Current through Register Vol. 46, No. 19, March 20, 2024
(2)
Definitions. For the
purpose of this chapter, the definitions of 641-Chapters 38 and 40 may also
apply. The following are specific to 641-Chapter 41.
"Accessible surface" means the external
surface of the enclosure or housing of the radiation producing machine as
provided by the manufacturer.
"Added filtration" means any filtration which
is in addition to the inherent filtration.
"Aluminum equivalent" means the thickness of
type 1100 aluminum alloy affording the same attenuation, under specified
conditions, as the material in question.
"Attenuation block" means a block or stack,
having dimensions 20 centimeters by 20 centimeters by 3.8 centimeters, of type
1100 aluminum alloy or other materials having equivalent attenuation.
"Automatic exposure control
(AEC)" means a device which automatically controls one or more
technique factors in order to obtain at a preselected location(s) a required
quantity of radiation (see also "Phototimer"). (Includes devices such as
phototimers and ion chambers.)
"Base density" means the optical density due
to the supporting base of the film alone. The base density of a film is the
optical density that would result if an unexposed film were processed through
the fixer, wash, and dryer, without first passing through the developer.
"Base plus fog density" means the optical
density of a film due to its base density plus any action of the developer on
the unexposed silver halide crystals. The base plus fog density can be measured
by processing an unexposed film through the entire processing cycle and
measuring the resultant optical density.
"Beam monitoring system" means a system
designed to detect and measure the radiation present in the useful beam.
"C-arm X-ray system" means an X-ray system in
which the image receptor and X-ray tube housing assembly are connected by a
common mechanical support system in order to maintain a desired spatial
relationship. This system is designed to allow a change in the projection of
the beam through the patient without a change in the position of the
patient.
"Cassette" means a light-tight case, usually
made of thin, low X-ray absorption plastic, for holding X-ray film. One or two
intensifying screens for the conversion of X-rays to visible light photons are
mounted inside the cassette so that they are in close contact to the
film.
"Cephalometric device" means a device intended
for the radiographic visualization and measurement of the dimensions of the
human head.
"Certified components" means components of
X-ray systems which are subject to regulations promulgated under Public Law
90-602, the "Radiation Control for Health and Safety Act of 1968," the Food and
Drug Administration.
"Certified system" means any X-ray system
which has one or more certified component(s).
"Coefficient of variation" or
"C" means the ratio of the standard deviation to the mean
value of a population of observations. It is estimated using the following
equation:
Click here
to view Image
where:
s= Estimated standard deviation of the
population.
X = Mean value of observations in sample.
Xi= ith
observation in sample.
n = Number of observations in sample.
"Computed tomography" means the production of
a tomogram by the acquisition and computer processing of X-ray transmission
data.
"Control chart" means a chart used to record
(and control) the results of quality control testing as a function of
time.
"Control limit" means the range of variation
on a control chart beyond which action must be taken to correct the results of
quality control testing.
"Control panel" (see X-ray control
panel).
"Cooling curve" means the graphical
relationship between heat units stored and cooling time.
"CT" (see "Computed tomography").
"Dead-man switch" means a switch so
constructed that a circuit closing contact can be maintained only by continuous
pressure on the switch by the operator.
"Dedicated mammography equipment" means X-ray
systems designed specifically for breast imaging, providing optimum imaging
geometry, a device for breast compression and low dose exposure that can
generate reproducible images of high quality.
"Densitometer" means an instrument which
measures the degree of blackening (or radiographic density) of film due to
radiation or light by measuring the ratio of the light intensity incident on
the film to the light intensity transmitted by the film.
"Detents" means mechanical settings that limit
or prevent the motion or rotation of an X-ray tube, cassette assembly, or image
receptor system.
"Developer" means a chemical solution
(alkaline) that changes the latent image (exposed silver halide crystals) on a
film to a visible image composed of minute masses of black metallic
silver.
"Developer replenishment" means the process,
occurring as film travels past a certain point in the processor, triggering the
activation of a pump, whereby fresh developer is added in small amounts to the
solution in the developer tank of the processor. The purpose is to maintain the
proper alkalinity, chemical activity, and level of solution in the developer
tank.
"Diagnostic mammography" means mammography
performed on an individual who, by virtue of symptoms or physical findings, is
considered to have a substantial likelihood of having breast disease.
"Diagnostic source assembly" means the tube
housing assembly with a beam-limiting device attached.
"Direct scattered radiation" means that
scattered radiation which has been deviated in direction only by materials
irradiated by the useful beam (see "Scattered radiation").
"Entrance exposure
rate" means the exposure free in air per unit time at the point where
the center of the useful beam enters the patient.
"Equipment" (see "X-ray equipment").
"Field emission equipment" means equipment
which uses an X-ray tube in which electron emission from the cathode is due
solely to the action of an electric field.
"Filter" means material placed in the useful
beam to preferentially absorb selected radiations.
"Fixer" means a chemical solution (acidic)
which removes the unexposed and undeveloped silver halide crystals from film so
it will not discolor or darken with age or exposure to light. Fixer also
hardens the gelatin containing the black metallic silver so film may be dried
and resist damage from abrasions.
"Fixer retention" means the inadequate removal
of fixer from the film by the water in the wash tank of the processor. Retained
fixer causes eventual brown discoloration of the radiograph.
"Fluoroscopic imaging assembly" means a
subsystem in which X-ray photons produce a visual image. It includes the image
receptor(s) such as the image intensifier and spot-film device, electrical
interlocks, if any, and structural material providing linkage between the image
receptor and diagnostic source assembly.
"Focal spot (actual)" means the area projected
on the anode of the X-ray tube bombarded by the electrons accelerated from the
cathode and from which the useful beam originates.
"Focal spot size" means the area of the target
or anode that is bombarded by electrons from the cathode of the X-ray tube to
produce X-rays. The smaller the focal spot, the better the limited spatial
resolution of the X-ray system, especially in magnification mammography.
"Fog" means the density added to a radiograph
due to unwanted action of the developer on the unexposed silver halide crystals
or by light, radiation, chemical, or heat exposure during storage, handling,
and processing.
"General purpose radiographic X-ray system"
means any radiographic X-ray system which, by design, is not limited to
radiographic examination of specific anatomical regions.
"Gonad shield" means a protective barrier for
the testes or ovaries.
"Healing arts screening" means the use of
radiation on human beings for the detection or evaluation of health indicators
for which the individual is considered at high risk when such tests are not
specifically and individually ordered by:
1. An individual authorized under
41.1(3)"a"(7), or
2. An individual licensed as a physician in
Iowa and listed as an authorized user on an NRC or agreement state radioactive
materials license.
"Heat unit" means a unit of energy equal to
the product of the peak kilovoltage, milliamperes, and seconds, i.e., kVp x mA
x second.
"Image contrast" means the amount of
radiographic density difference between adjacent areas resulting from a fixed
amount of attentuation difference or light exposure difference.
"Image intensifier" means a device, installed
in its housing, which instantaneously converts an X-ray pattern into a
corresponding light image of higher energy intensity.
"Image noise" See "Radiographic noise."
"Image quality" means the overall clarity and
detail of a radiographic image. Limiting spatial resolution (or resolving
power), image sharpness, and image contrast are three common measures of image
quality.
"Image receptor" means any device, such as a
fluorescent screen or radiographic film, which transforms incident X-ray
photons either into a visible image or into another form which can be made into
a visible image by further transformations.
"Image sharpness" means the overall impression
of detail and clarity in a radiographic image.
"Inherent filtration" means the filtration of
the useful beam provided by the permanently installed components of the tube
housing assembly.
"Kilovolts peak" (see "Peak tube
potential").
"kVp" (see "Peak tube potential").
"kWs" means kilowatt second.
"Leakage technique factors" means the
technique factors associated with the diagnostic or therapeutic source assembly
which are used in measuring leakage radiation. They are defined as
follows:
a. For diagnostic source
assemblies intended for capacitor energy storage equipment, the maximum rated
peak tube potential and the maximum-rated number of exposures in an hour for
operation at the maximum-rated peak tube potential with the quantity of charge
per exposure being 10 millicoulombs, i.e., 10 milliampere seconds, or the
minimum obtainable from the unit, whichever is larger.
b. For diagnostic source assemblies intended
for field emission equipment rated for pulsed operation, the maximum-rated peak
tube potential and the maximum-rated number of X-ray pulses in an hour for
operation at the maximum-rated peak tube potential.
c. For all other diagnostic or therapeutic
source assemblies, the maximum-rated peak tube potential and the maximum-rated
continuous tube current for the maximum-rated peak tube potential.
"Linear attenuation coefficient" or "µ"
means the quotient of dN/N divided by dl when dN/N is the fraction of uncharged
ionizing radiation that experience interactions in traversing a distance dl in
a specified material.
"Line-voltage regulation" means the difference
between the no-load and the load line potentials expressed as a percent of the
load line potential. It is calculated using the following equation:
Percent line-voltage regulation = 100
(Vn-Vl)/Vl
where
Vn = No-load line potential and
Vl = Load line potential.
"mAs" means milliampere second.
"Maximum line current" means the
root-mean-square current in the supply line of an X-ray machine operating at
its maximum rating.
"Mobile X-ray equipment" (see "X-ray
equipment").
"PBL" (see "Positive beam limitation").
"Phototimer" means a method for controlling
radiation exposures to image receptors by the amount
of radiation which reaches a radiation-monitoring device(s). The
radiation-monitoring device(s) is part of an electronic circuit which controls
the duration of time the tube is activated (see "Automatic
exposure control").
"PID" (see "Position indicating
device").
"Portable X-ray equipment" (see "X-ray
equipment").
"Position indicating device" means a device on
dental X-ray equipment used to indicate the beam position and to establish a
definite source-surface (skin) distance. It may or may not incorporate or serve
as a beam-limiting device.
"Positive beam limitation" means the automatic
or semiautomatic adjustment of an X-ray beam to the size of the selected image
receptor, whereby exposures cannot be made without such adjustment.
"Processor" means an automated device which
transports film in a controlled manner by a system of rollers through
specialized sections where developing, fixing, washing, and drying of the film
occur.
"Protective apron" means an apron made of
radiation-absorbing materials used to reduce radiation exposure.
"Protective glove" means a glove made of
radiation-absorbing materials used to reduce radiation exposure.
"Quality assurance" means the overall program
of testing and maintaining the highest possible standards of quality in the
acquisition and interpretation of radiographic images.
"Quality control" means the actual process of
testing and maintaining the highest possible standards of quality in equipment
performance and the acquisition and interpretation of radiographic
images.
"Radiation therapy simulation system" means a
radiographic or fluoroscopic X-ray system intended for localizing the volume to
be exposed during radiation therapy and confirming the position and size of the
therapeutic irradiation field.
"Radiograph" means an image receptor on which
the image is created directly or indirectly by an X-ray pattern and results in
a permanent record.
"Radiographic contrast" means the magnitude of
optical density difference between structures of interest and their
surroundings, or between areas of film receiving different amount of X-ray or
visible light exposure.
"Radiographic noise" means unwanted
fluctuations in optical density on the screen-film image.
"Rating" means the operating limits as
specified by the component manufacturer.
"Recording" means producing a permanent form
of an image resulting from X-ray photons.
"Repeat (or reject) analysis" means a
systematic approach to determine the causes for radiographs being discarded or
repeated, or both.
"Replenishment rate" means the amount of
chemicals added in order to maintain the proper chemical activity of developer
and fixer solutions.
"Response time" means the time required for an
instrument system to reach 90 percent of its final reading when the
radiation-sensitive volume of the instrument system is exposed to a step change
in radiation flux from zero sufficient to provide a steady state midscale
reading.
"Safelight" means a source of minimal visible
light in a darkroom, produced at frequencies (colors) to which the film is
insensitive, protecting the film from unwanted exposure (fog) while allowing
personnel to function more efficiently and safely.
"Screen" means microscopic phosphor crystals
on a plastic support used in conjunction with either single or double emulsion
film; the screen emits visible light when exposed to X-radiation, creating a
latent image on X-ray film.
"Screen-film combination" means a particular
intensifying screen used with a particular type of film. Care must be taken to
match the number of screens (one or two) to the number of emulsions coating the
film and to match the light output spectrum of the screen to the light
sensitivity of the film.
"Screen-film contact" means the close
proximity of the intensifying screen to the emulsion of the film, necessary in
order to achieve a sharp image on the film.
"Sensitometer" means a device used to
reproducibly expose a piece of film to a number of different levels of light
intensity.
"Sensitometric strip" means a sheet of film
exposed by a sensitometer, resulting in a gray scale range. Such strips are
used to measure the range of densities, from minimum to maximum, resulting from
a reproducible set of exposures.
"Sensitometry" means a quantitative
measurement of the response of film to exposure and development. Sensitometry
is used to test the processor setup and stability.
"SID" (see "Source-image receptor
distance").
"Source" means the focal spot of the X-ray
tube.
"Source-image receptor distance" means the
distance from the source to the center of the input surface of the image
receptor.
"Spot check" means a procedure which is
performed to ensure that a previous calibration continues to be valid.
"Spot film" means a radiograph which is made
during a fluoroscopic examination to permanently record conditions which exist
during that fluoroscopic procedure.
"Spot-film device" means a device intended to
transport or position a radiographic image receptor between the X-ray source
and fluoroscopic image receptor. It includes a device intended to hold a
cassette over the input end of an image intensifier for the purpose of making a
radiograph.
"Stationary X-ray equipment" (see "X-ray
equipment").
"Technique factors" means the following
conditions of operation:
a. For
capacitor energy storage equipment, peak tube potential in kV and quantity of
charge in mAs;
b. For field
emission equipment rated for pulsed operation, peak tube potential in kV, and
number of X-ray pulses;
c. For CT
X-ray systems designed for pulsed operation, peak tube potential in kV, scan
time in seconds, and either tube current in mA, X-ray pulse width in seconds,
and the number of X-ray pulses per scan, or the product of tube current, X-ray
pulse width, and the number of X-ray pulses in mAs;
d. For CT X-ray systems not designed for
pulsed operation, peak tube potential in kV, and either tube current in mA and
scan time in seconds, or the product of tube current and exposure time in mAs
and the scan time when the scan time and exposure time are equivalent;
and
e. For all other equipment,
peak tube potential in kV, and either tube current in mA and exposure time in
seconds, or the product of tube current and exposure time in mAs.
"Tomogram" means the depiction of the X-ray
attenuation properties of a section through the body.
"Tube rating chart" means the set of curves
which specify the rated limits of operation of the tube in terms of the
technique factors.
"Useful beam" means the radiation emanating
from the tube housing port or the radiation head and passing through the
aperture of the beam-limiting device when the exposure controls are in a mode
to cause the system to produce radiation.
"Variable-aperture beam-limiting device" means
a beam-limiting device which has capacity for stepless adjustment of the X-ray
field size at a given SID.
"Viewbox" means a device by which a uniform
field of white light is transmitted through an X-ray so that the image on the
film may be seen.
"Visible area" means that portion of the input
surface of the image receptor over which incident X-ray photons are producing a
visible image.
"X-ray control panel" means a device which
controls input power to the X-ray high-voltage generator and the X-ray tube. It
includes equipment such as timers, phototimers, automatic brightness
stabilizers, and similar devices, which control the technique factors of an
X-ray exposure.
"X-ray equipment" means an X-ray system,
subsystem, or component thereof. Types of X-ray equipment are as
follows:
a.
"Mobile X-ray
equipment" means X-ray equipment mounted on a permanent base with
wheels or casters for moving while completely assembled.
b.
"Portable X-ray
equipment" means X-ray equipment designed to be hand-carried but used
with a tripod or other stabilization mechanism so the operator is not holding
the equipment during exposure.
c.
"Stationary X-ray equipment" means X-ray equipment which is
installed in a fixed location.
d.
"Handheld X-ray equipment" means X-ray equipment designed by
the manufacturer to be handheld by the operator during the exposure. X-ray
equipment designed without a backscatter shield is prohibited.
"X-ray exposure control" means a device,
switch, button or similar means by which an operator initiates or terminates
the radiation exposure. The X-ray exposure control may include such associated
equipment as timers and backup timers.
"X-ray field" means that area of the
intersection of the useful beam and any one of the set of planes parallel to
and including the plane of the image receptor, whose perimeter is the locus of
points at which the exposure rate is one-fourth of the
maximum in the intersection.
"X-ray high-voltage generator" means a device
which transforms electrical energy from the potential supplied by the X-ray
control to the tube operating potential. The device may also include means for
transforming alternating current to direct current, filament transformers for
the X-ray tube(s), high-voltage switches, electrical protective devices, and
other appropriate elements.
"X-ray system" means an assemblage of
components for the controlled production of X-rays. It includes minimally an
X-ray high-voltage generator, an X-ray control, a tube housing assembly, a
beam-limiting device, and the necessary supporting structures. Additional
components which function with the system are considered integral parts of the
system.
"X-ray table" means a patient support device
with its patient support structure (tabletop) interposed between the patient
and the image receptor during radiography or fluoroscopy. This includes, but is
not limited to, any stretcher equipped with a radiolucent panel and any table
equipped with a cassette tray (or bucky), cassette tunnel, image intensifier,
or spot-film device beneath the tabletop.
(3)
Administrative controls.
a. Registrant. The registrant shall be
responsible for maintaining and directing the operation of the X-ray system(s)
under the registrant's administrative control, for ensuring that the
requirements of these rules are met in the operation of the X-ray system(s),
and for having the following minimum tests performed by a registered service
facility according to the following schedule:
1. Medical/chiropractic: timer accuracy,
exposure reproducibility, kVp accuracy as set forth in 41.1(6), and light
field/X-ray field alignment as set forth in 41.1(6) every two years.
2. Dental/podiatry: timer accuracy, exposure
reproducibility and kVp accuracy as set forth in 41.1(7) every four
years.
3. Fluoroscopic: entrance
exposurerate (41.1(5)"c"), and
minimum SSD (41.1(5)"f") annually.
4. Veterinary systems are exempt from the
above testing requirements.
All service and installation shall be performed by persons
registered under 641-subrule 39.3(3). The registrant or the registrant's agent
shall ensure that the requirements of these rules are met in the operation of
the X-ray system(s).
(1) An X-ray
system which does not meet the provisions of these rules shall not be operated
for diagnostic or therapeutic purposes unless so directed by the agency. All
position locking, holding, and centering devices on X-ray system components and
systems shall function as intended. All X-ray systems shall be maintained in
good mechanical repair and comply with all state and local electrical code
requirements.
(2) Individuals who
will be operating the X-ray systems shall be adequately instructed in safe
operating procedures and be competent in the safe use of the equipment. In
addition:
1. Operators in medical facilities
shall meet the requirements of 641-Chapter 42, as applicable, and shall make
the permit available at the individual's place of employment. If the permit
holder works at more than one facility, a duplicate of the permit shall be kept
at each facility.
(3) A
chart shall be provided in the vicinity of the diagnostic X-ray system's
control panel which specifies, for all examinations performed with that system,
the appropriate technique and guidance for employing available dose reduction
methods and technologies across all patient sizes and clinical indications. The
following information shall be included:
1.
Patient's body part and anatomical size, or body part thickness, or age (for
pediatrics), versus technique factors to be utilized unless automatically set
by the X-ray system;
2. Type and
size of the film or film-screen combination to be used;
3. Type and focal distance of the grid to be
used, if any; and
4. Source to
image receptor distance to be used, except for dental intraoral
radiography.
(4) Written
safety procedures shall be provided to each individual operating X-ray
equipment, including patient holding and any restrictions of the operating
technique required for the safe operation of the particular X-ray system. The
operator shall be able to demonstrate familiarity with these
procedures.
(5) Except for patients
who cannot be moved out of the room, only the staff and ancillary personnel
required for the medical procedure or training shall be in the room during the
radiographic exposure. Other than the patient being examined:
1. All individuals shall be positioned such
that no part of the body will be struck by the useful beam unless protected by
0.5 millimeter lead equivalent.
2.
The X-ray operator, other staff, ancillary personnel, and other persons
required for the medical procedure shall be protected from the scattered
primary radiation by protective aprons or whole body protective barriers of not
less than 0.25 millimeter lead equivalent.
3. Human patients who cannot be removed from
the room shall be protected from the direct scatter radiation by whole body
protective barriers of 0.25 millimeter lead equivalent or shall be so
positioned that the nearest portion of the body is at least 2 meters from both
the tube head and the nearest edge of the image receptor.
(6) A sufficient number of protective apparel
(e.g., aprons, gloves, collars) and shields shall be available to provide the
necessary radiation protection for all patients and personnel who are involved
with X-ray operations.
(7)
Individuals shall not be exposed to the useful beam unless (1) the radiation
exposure occurs in the context of a previously established professional
relationship between a licensed practitioner of the healing arts or a licensed
registered nurse who is registered as an advanced registered nurse practitioner
pursuant to Iowa Code chapter 152 and a patient, which includes a physical
examination by the practitioner of the patient unless such examination is not
clinically indicated; and (2) such practitioner issues a written order for the
radiation exposure. The written order shall be issued prior to the exposure
unless the exposure results from care provided in an emergency or surgery
setting. A verbal order may be issued provided the licensed practitioner is
supervising the procedure and the order is documented in the patient's record
after the procedure is completed. This provision specifically prohibits
deliberate exposure for the following purposes:
1. Exposure of an individual for training,
demonstration, or other non-healing arts purposes; and
2. Exposure of an individual for the purpose
of healing arts screening except as authorized by 41.1(3)
"a"(11).
(8) When a patient or film must be provided
with auxiliary support during a radiation exposure:
1. Mechanical holding devices shall be used
when the technique permits. The written safety procedures, required by
41.1(3)"a"(4), shall list individual projections where holding
devices cannot be utilized;
2.
Written safety procedures, as required by 41.1(3)"a"(4), shall
indicate the requirements for selecting a holder and the procedure the holder
shall follow;
3. The human holder
shall be instructed in personal radiation safety and protected as required by
41.1(3)"a"(5)"2";
4. No individual shall be used routinely to
hold film or patients; and
5. In
those cases where the human patient must hold the film, except during intraoral
examinations, any portion of the body other than the area of clinical interest
struck by the useful beam shall be protected by not less than 0.5 millimeter
lead equivalent material.
6. Each
facility shall have leaded aprons and gloves available in sufficient numbers to
provide protection to all personnel who are involved with X-ray operations and
who are otherwise not shielded.
(9) Procedures and auxiliary equipment
designed to minimize patient and personnel exposure commensurate with the
needed diagnostic information shall be utilized.
1. The speed of film or screen and film
combinations shall be the fastest speed consistent with the diagnostic
objective of the examinations. Film cassettes without intensifying screens
shall not be used for any routine diagnostic radiological imaging, with the
exception of veterinary radiography and standard film packets for intraoral use
in dental radiography.
2. The
radiation exposure to the patient shall be the minimum exposure required to
produce images of good diagnostic quality.
3. Portable or mobile X-ray equipment shall
be used only for examinations, excluding intraoral dental imaging, where it is
impractical to transfer the patient(s) to a stationary X-ray installation.
Handheld mobile X-ray equipment may be used for routine intraoral dental
imaging in place of stationary equipment. Handheld X-ray equipment shall be
used only for intraoral dental radiography.
4. X-ray systems subject to 41.1(6) shall not
be utilized in procedures where the source to human patient distance is less
than 30 centimeters.
5. If grids
are used between the patient and the image receptor to decrease scatter to the
film and improve contrast, the grid shall:
* Be positioned properly, i.e., tube side facing the correct
direction, and the grid centered to the central ray;
* If the grid is of the focused type, be at the proper focal
distance for the SIDs being used.
(10) All individuals who are associated with
the operation of an X-ray system are subject to the requirements of 641-subrule
40.36(4) and rules 641-40.15 (136C) and
641-40.37 (136C). In addition:
1. When protective clothing or devices are
worn on portions of the body and a personnel monitoring device(s) is present,
it (they) shall be worn in accordance with the recommendations found in Chapter
4 of the National Council of Radiation Protection and Measurements Report No.
57.
2. Exposure of a personnel
monitoring device to deceptively indicate a dose delivered to an individual is
prohibited.
(11) Healing
arts screening. Any person proposing to conduct a healing arts screening
program shall not initiate such a program in the state of Iowa without prior
written approval of the agency. When requesting such approval, that person
shall submit the information outlined in Appendix C of this chapter. The agency
shall not approve a healing arts screening program unless the applicant submits
data supporting the efficacy of the screening test in diagnosing the disease or
condition being screened. If any information submitted to the agency becomes
invalid or outdated, the applicant shall notify the agency in writing within
five calendar days.
b. Information and maintenance record and
associated information. Records in 41.1(3)
"b"(1) and (3) below
shall be maintained until the X-ray system is removed from the facility. There
shall be two cycles of records on file for items in
41.1(3)
"b"(2) below. The registrant shall maintain the
following information for each X-ray system for inspection by the agency:
(1) User's manual for the X-ray
system;
(2) Records of surveys,
calibrations, maintenance, and modifications performed on the X-ray system(s)
with the names of persons who performed such services;
(3) A copy of all correspondence with this
agency regarding that X-ray system.
c. X-ray utilization log. Except for
veterinary facilities, each facility shall maintain an X-ray log containing the
patient's name, the type of examinations, the dates the examinations were
performed, the name of the individual performing the X-ray procedure, and the
number of exposures and retakes involved. When the patient or film must be
provided with human auxiliary support, the name of the human holder shall be
recorded. These records shall be kept until the facility is inspected by this
agency or until all films listed on the utilization log have been
purged.
d. Plan review.
(1) Prior to construction of all new
installations, or modifications of existing installations, or installation of
equipment into existing facilities utilizing X-rays for diagnostic or
therapeutic purposes, the floor plans and equipment arrangements shall be
submitted to the agency for review and verification that national standards
have been met. The required information is denoted in Appendices A and B of
this chapter.
(2) The agency may
require the applicant to utilize the services of a qualified expert to
determine the shielding requirements prior to the plan review and
approval.
(3) The approval of such
plans shall not preclude the requirement of additional modifications should a
subsequent analysis of operating conditions indicate the possibility of an
individual receiving a dose in excess of the limits prescribed in 641-Chapter
40.
e. Federal
performance standards. All X-ray equipment shall comply with the applicable
performance standards of
21 CFR
1020.30 to
1020.40
which were in effect at the time the unit was manufactured. All equipment
manufactured before the effective date of
21 CFR
1020.30 to
1020.40
shall meet the requirements of the Iowa rules. Persons registered to possess
the affected radiation-emitting equipment in Iowa shall be responsible for
maintaining the equipment in compliance with the appropriate federal
performance standards.
f. X-ray
film processing facilities and practices (except for mammography). Each
installation using a radiographic X-ray system and using analog image receptors
(e.g., radiographic film) shall have available suitable equipment for handling
and processing radiographic film in accordance with the following provisions:
(1) Manually developed film.
1. Processing tanks shall be constructed of
mechanically rigid, corrosion-resistant material; and
2. Film shall be processed in accordance with
the time-temperature relationships recommended by the film developer
manufacturer. The specified developer temperature and immersion time shall be
posted in the darkroom. Deviations from the manufacturer's recommendations
shall be in writing and on file at the facility. Documentation shall include
justification for the deviation.
3.
Devices shall be utilized which will indicate the actual temperature of the
developer and signal the passage of a preset time appropriate to the developing
time required.
(2)
Automatic processors and other closed processing systems.
1. Film shall be processed in accordance with
the time-temperature relationships recommended by the film developer
manufacturer.
2. Processing
deviations from the requirements of 41.1(3)"f" shall be
documented by the registrant in such manner that the requirements are shown to
be met or exceeded (e.g., extended processing and special rapid
chemistry).
3. All processing
equipment shall be in good mechanical working order.
(3) Other requirements.
1. Pass boxes, if provided, shall be so
constructed as to exclude light from the darkroom when cassettes are placed in
or removed from the boxes, and shall incorporate adequate shielding from stray
radiation to prevent exposure of undeveloped film.
2. The darkroom shall be light tight and use
proper safelighting such that any film type in use exposed in a cassette to
X-radiation sufficient to produce an optical density from 1 to 2 when processed
shall not suffer an increase in density greater than 0.1 when exposed out of
the cassette in the darkroom for 2 minutes with all safelights on. If used,
daylight film handling boxes shall preclude fogging of the film.
3. Darkrooms typically used by more than one
individual shall be provided a method to prevent accidental entry while
undeveloped films are being handled or processed.
4. Film shall be stored in a cool, dry place
and shall be protected from exposure to stray radiation. Film in open packages
shall be stored in a light tight container.
5. Film cassettes and intensifying screens
shall be inspected periodically and shall be cleaned and replaced as necessary
to best ensure radiographs of good diagnostic quality.
6. Outdated X-ray film shall not be used for
diagnostic radiographs, unless the film has been stored in accordance with the
manufacturer's recommendations and a sample of the film passes a sensitometric
test for normal ranges of base plus fog and speed.
7. Film developing solutions shall be
prepared in accordance with the directions given by the manufacturer and shall
be maintained in strength by replenishment or renewal so that full development
is accomplished within the time specified by the manufacturer.
(4) Records shall be maintained to
verify that the items in 41.1(3)"f" are performed according to
the requirements. Records may be discarded only after an agency inspection has
been completed and the facility determined to be in compliance.
g. Retention of films. Record
retention of films shall be seven years for patients 18 years of age or older
and seven years plus the difference between the patient's age and 18 for
minors.
(1) If the facility is currently
utilizing hard-copy film to store images, it may continue to use this method
throughout the retention period.
(2) If the facility is currently utilizing
computer media and also storing images in a hard-copy format, it may continue
to use this method of retention throughout the retention period. If the images
are also on computer media, the data should be backed up, or refreshed, at
appropriate intervals as defined by the facility.
(3) If the facility is solely utilizing
computer media to store study information for which a report is generated, the
recording media is to be stored in conditions that will ensure that
deterioration will not occur for the period required by this policy. The
facility must maintain either retrieval or access or both to the stored
images.
(4) If a patient's medical
images are identified as being involved in a legal case, the records should
immediately be coded appropriately, and maintained for the required time frame
defined in this paragraph. At the time the records have reached the end of the
appropriate time frame for retention, the previously identified responsible
individuals involved in the legal action should be contacted for further
instruction.
(5) If records are
temporarily transferred to any party, appropriate information relating to
location, date of release, and individual having custody of the records should
be maintained.
(6) A facility that
is ceasing operations must either transfer its film records to another facility
or provide the film records to its patients. A certified letter as to the
location, or disposition, of the film records must be sent to notify the
patients of the transferal.
(4)
General requirements for all
diagnostic X-ray systems. In addition to other requirements of this
chapter, all diagnostic X-ray systems shall meet the following requirements:
a. Warning label. The control panel
containing the main power switch shall bear the warning statement, legible and
accessible to view: "WARNING: This X-ray unit may be dangerous to patient and
operator unless safe exposure factors and operating instructions are
observed."
b. Battery charge
indicator. On battery-powered X-ray generators, visual means shall be provided
on the control panel to indicate whether the battery is in a state of charge
adequate for proper operation.
c.
Leakage radiation from the diagnostic source assembly. The leakage radiation
from the diagnostic source assembly measured at a distance of 1 meter in any
direction from the source shall not exceed 100 milliroentgens (25.8
µC/kg) in one hour when the X-ray tube is operated at
its leakage technique factors. Compliance shall be determined by measurements
averaged over an area of 100 square centimeters with no linear dimension
greater than 20 centimeters.
d.
Radiation from components other than the diagnostic source assembly. The
radiation emitted by a component other than the diagnostic source assembly
shall not exceed 2 milliroentgens (0.516 µC/kg) in one
hour at 5 centimeters from any accessible surface of the component when it is
operated in an assembled X-ray system under any conditions for which it was
designed. Compliance shall be determined by measurements averaged over an area
of 100 square centimeters with no linear dimension greater than 20
centimeters.
e. Beam quality.
(1) Half-value layer.
1. The half-value layer of the useful beam
for a given X-ray tube potential shall not be less than the values shown in
Table I. If it is necessary to determine such half-value layer at an X-ray tube
potential which is not listed in Table I, linear interpolation or extrapolation
may be made.
Table I
|
Design operating range (kVp)
|
Measured potential (kVp)
|
Half-value layer (mm of aluminum)
|
|
Below 50 ..............
|
30
|
0.3
|
|
40
|
0.4
|
|
49
|
0.5
|
|
50 to 70 ...............
|
50 |
1.2
|
|
60
|
1.3
|
|
70
|
1.5
|
|
Above 70 ..............
|
71
|
2.1
|
|
80
|
2.3
|
|
90
|
2.5
|
|
100
|
2.7
|
|
110
|
3.0
|
|
120
|
3.2
|
|
130
|
3.5
|
|
140
|
3.8
|
|
150
|
4.1
|
2. and
3. Reserved.
4. For capacitor
energy storage equipment, compliance with the requirements of
41.1(4)"e" shall be determined with the system fully charged
and a setting of 10 mAs for each exposure.
5. The required minimal half-value layer of
the useful beam shall include the filtration contributed by all materials which
are permanently between the source and the patient.
(2) Filtration controls. For X-ray systems
which have variable kVp and variable filtration for the useful beam, a device
shall link the kVp selector with the filter(s) and shall prevent an exposure
unless the minimum amount of filtration required by
41.1(4)"e"(1)"1" is in the useful beam for the given kVp which
has been selected.
f.
Multiple tubes. Where two or more radiographic tubes are controlled by one
exposure switch, the tube or tubes which have been selected shall be clearly
indicated prior to initiation of the exposure. This indication shall be both on
the X-ray control panel and at or near the tube housing assembly which has been
selected.
g. Mechanical support of
tube head. The tube housing assembly supports shall be adjusted such that the
tube housing assembly will remain stable during an exposure unless tube housing
movement is a designed function of the X-ray system.
h. Technique indicators.
(1) The technique factors to be used during
an exposure shall be indicated before the exposure begins. If automatic
exposure controls are used, the technique factors
which are set prior to the exposure shall be indicated.
(2) The requirement of
41.1(4)"h"(1) may be met by permanent markings on equipment
having fixed technique factors. Indication of technique factors shall be
visible from the operator's position except in the case of spot films made by
the fluoroscopist.
(3) The
technique indicators shall be accurate to within manufacturer's
standards.
(5)
Fluoroscopic X-ray systems except for computed tomography X-ray
systems. All fluoroscopic X-ray systems shall be image intensified and
meet the following requirements:
a.
Limitation of useful beam.
(1) Primary
barrier.
1. The fluoroscopic imaging assembly
shall be provided with a primary protective barrier which intercepts the entire
cross section of the useful beam at any SID.
2. The X-ray tube used for fluoroscopy shall
not produce X-rays unless the barrier is in position to intercept the entire
useful beam.
(2)
Fluoroscopic beam limitation.
1. For certified
fluoroscopic systems with or without a spot film device, neither the length nor
the width of the X-ray field in the plane of the image receptor shall exceed
that of the visible area of the image receptor by more than 3 percent of the
SID. The sum of the excess length and the excess width shall be no greater than
4 percent of the SID.
2. For
uncertified fluoroscopic systems with a spot film device, the X-ray beam with
the shutter fully opened (during fluoroscopy or spot filming) shall be no
larger than the largest spot film size for which the device is designed.
Measurements shall be made at the maximum SID available but at no less than 20
centimeters from the tabletop to the film plane distance.
3. For uncertified fluoroscopic systems
without a spot film device, the requirements of
41.1(5)"a"(2)"1" apply.
4. Other requirements for fluoroscopic beam
limitation:
* Means shall be provided to permit further limitation of the
field. Beam-limiting devices manufactured after May 22, 1979, and incorporated
in equipment with a variable SID or a visible area of greater than 300 square
centimeters shall be provided with means for stepless adjustment of the X-ray
field;
* All equipment with a fixed SID and a visible area of 300
square centimeters or less shall be provided either with stepless adjustment of
the X-ray field or with means to further limit the X-ray field size at the
plane of the image receptor to 125 square centimeters or less;
* If provided, stepless adjustment shall, at the greatest SID,
provide continuous field sizes from the maximum attainable to a field size of 5
centimeters by 5 centimeters or less;
* For equipment manufactured after February 25, 1978, when the
angle between the image receptor and beam axis is variable, means shall be
provided to indicate when the axis of the X-ray beam is perpendicular to the
plane of the image receptor;
* For noncircular X-ray fields used with circular image
receptors, the error in alignment shall be determined along the length and
width dimensions of the X-ray field which pass through the center of the
visible area of the image receptor.
(3) Spot-film beam limitation. Spot-film
devices shall meet the following requirements:
1. Means shall be provided between the source
and the patient for adjustment of the X-ray field size in the plane of the film
to the size of that portion of the film which has been selected on the
spot-film selector. Such adjustment shall be automatically accomplished except
when the X-ray field size in the plane of the film is smaller than that of the
selected portion of the film. For spot-film devices manufactured after June 21,
1979, if the X-ray field size is less than the size of the selected portion of
the film, the means for adjustment of the field size shall be only at the
operator's option;
2. Neither the
length nor the width of the X-ray field in the plane of the image receptor
shall differ from the corresponding dimensions of the selected portion of the
image receptor by more than 3 percent of the SID when adjusted for full
coverage of the selected portion of the image receptor. The sum, without regard
to sign, of the length and width differences shall not exceed 4 percent of the
SID;
3. It shall be possible to
adjust the X-ray field size in the plane of the film to a size smaller than the
selected portion of the film. The minimum field size at the greatest SID shall
be equal to, or less than, 5 centimeters by 5 centimeters;
4. The center of the X-ray field in the plane
of the film shall be aligned with the center of the selected portion of the
film to within 2 percent of the SID; and
5. On spot-film devices manufactured after
February 25, 1978, if the angle between the plane of the image receptor and
beam axis is variable, means shall be provided to indicate when the axis of the
X-ray beam is perpendicular to the plane of the image receptor, and compliance
shall be determined with the beam axis indicated to be perpendicular to the
plane of the image receptor.
(4) Override. If a means exists to override
any of the automatic X-ray field size adjustments required in
41.1(5)
"a"(2) and 41.1(5)
"a"(3), that means:
1. Shall be designed for use only in the
event of system failure;
2. Shall
incorporate a signal visible at the fluoroscopist's position which will
indicate whenever the automatic field size adjustment is overridden;
and
3. Shall have a clear and
durable label as follows:
FOR X-RAY FIELD
LIMITATION SYSTEM FAILURE
b. Activation of the fluoroscopic tube. X-ray
production in the fluoroscopic mode shall be controlled by a device which
requires continuous pressure by the fluoroscopist for the entire time of any
exposure. When recording serial fluoroscopic images, the fluoroscopist shall be
able to terminate the X-ray exposure(s) at any time, but means may be provided
to permit completion of any single exposure of the series in process.
c.
exposurerate
limits.
(1) Entrance
exposure rate allowable limits.
1. Fluoroscopic equipment which is provided
with automatic
exposure rate control shall not be
operable at any combination of tube potential and current which will result in
an
exposure rate in excess of 2.6 mC/kg (10 roentgens)
per minute at the point where the center of the useful beam enters the patient,
except
* During recording of fluoroscopic images; or
* When an optional high level control is provided. When so
provided, the equipment shall not be operable at any combination of tube
potential and current which will result in an exposure
rate in excess of 5 roentgens (1.3 mC/kg) per minute at the point where the
center of the useful beam enters the patient unless the high level control is
activated. Special means of activation of high level controls shall be
required. The high level control shall only be operable when continuous manual
activation is provided by the operator. A continuous signal audible to the
fluoroscopist shall indicate that the high level control is being
employed.
2. Fluoroscopic
equipment which is not provided with automatic
exposure rate control shall not be operable at any
combination of tube potential and current which will result in an
exposure rate in excess of 5 roentgens (1.3 mC/kg) per
minute at the point where the center of the useful beam enters the patient,
except:
* During recording of fluoroscopic images; or
* When the mode or modes have an optional high level control,
in which case the mode or modes shall not be operable at any combination of
tube potential and current which shall result in an
exposure rate in excess of 5 roentgens (1.3 mC/kg) per
minute at the point where the center of the useful beam enters the patient,
unless the high level control is activated. Special means of activation of high
level controls shall be required. The high level control shall only be operable
when continuous manual activation is provided by the operator. A continuous
signal audible to the fluoroscopist shall indicate that the high level control
is being employed.
3.
Compliance with the requirements of 41.1(5)
"c" shall be
determined as follows:
* If the source is below the table,
exposure rate shall be measured 1 centimeter above the
tabletop or cradle;
* If the source is above the table, the
exposure rate shall be measured at 30 centimeters
above the tabletop with the end of the beam-limiting device or spacer
positioned as closely as possible to the point of measurement;
* All C-arm fluoroscopes, both stationary and mobile, shall
meet the entrance exposure rate limits at 30
centimeters from the input surface of the fluoroscopic imaging assembly with
the source positioned at any available SID provided that the end of the spacer
assembly or beam-limiting device is not closer than 30 centimeters from the
input surface of the fluoroscopic imaging assembly.
* For a lateral type fluoroscope, the
exposure rate shall be measured at a point 15
centimeters from the centerline of the X-ray table and in the direction of the
X-ray source with the end of the beam-limiting device or spacer positioned as
closely as possible to the point of measurement. If the tabletop is movable, it
shall be positioned as closely as possible to the lateral X-ray source, with
the end of the beam-limiting device or spacer no closer than 15 centimeters to
the centerline of the X-ray table.
4. Fluoroscopic equipment which is provided
with both automatic exposure rate control mode and a manual mode shall not be
operable at any combination of tube potential and current which shall result in
an exposure rate in excess of 10 roentgens (2.6 mC/kg) per minute in either
mode at the point where the center of the useful beam enters the patient,
except:
* During recording of fluoroscopic images; or
* When the mode or modes have an optional high level control,
in which case the mode or modes shall not be operable at any combination of
tube potential and current which shall result in an exposure rate in excess of
5 roentgens (1.3 mC/kg) per minute at the point where the center of the useful
beam enters the patient, unless the high level control is activated. Special
means of activitation of high level controls shall be required. The high level
control shall only be operable when continuous manual activitation is provided
by the operator. A continuous signal audible to the fluroscopist shall indicate
that the high level control is being employed.
5. Any fluoroscopic equipment manufactured
after May 19, 1995, which can exceed 5 roentgens (1.3 mC/kg) per minute shall
be equipped with an automatic exposure rate control. All entrance exposure rate
limits shall be 10 roentgens (2.6 mC/kg) per minute with an upper limit of 20
roentgens (5.2 mC/kg) per minute when the high level control is
activated.
6. Conditions of
periodic measurement of maximum entrance
exposure rate
are as follows:
* The measurement shall be made under the conditions that
satisfy the requirements of 41.1(5) "c"(1)"3";
* The kVp, mA, or other selectable parameters shall be adjusted
to those settings which give the maximum entrance
exposure rate;
* The X-ray system(s) that incorporates automatic
exposure rate control shall have sufficient
attenuative material placed in the useful beam to produce either a
milliamperage or kilovoltage or both to satisfy the conditions of
41.1(5)"c"(1)"3."
(2) Reserved.
d. Barrier transmitted radiation rate limits.
(1) The exposure
rate due to transmission through the primary protective barrier with the
attenuation block in the useful beam, combined with radiation from the image
intensifier, if provided, shall not exceed 2 milliroentgens (0.516
µC/kg) per hour at 10 centimeters from any accessible
surface of the fluoroscopic imaging assembly beyond the plane of the image
receptor for each roentgen per minute of entrance
exposure rate.
(2) Measuring compliance of barrier
transmission.
1. The
exposure rate due to transmission through the primary
protective barrier combined with radiation from the image intensifier shall be
determined by measurements averaged over an area of 100 square centimeters with
no linear dimension greater than 20 centimeters.
2. If the source is below the tabletop, the
measurement shall be made with the input surface of the fluoroscopic imaging
assembly positioned 30 centimeters above the tabletop.
3. If the source is above the tabletop and
the SID is variable, the measurement shall be made with the end of the
beam-limiting device or spacer as close to the tabletop as it can be placed,
provided that it shall not be closer than 30 centimeters.
4. Movable grids and compression devices
shall be removed from the useful beam during the measurement.
e. Indication of
potential and current. During fluoroscopy and cinefluorography the kV and the
mA shall be continuously indicated.
f. Source-to-skin distance. The SSD shall not
be less than:
(1) 38 centimeters on stationary
fluoroscopes installed on or after August 1, 1974,
(2) 35.5 centimeters on stationary
fluoroscopes which were in operation prior to August 1, 1974,
(3) 30 centimeters on all mobile
fluoroscopes, and
(4) 20
centimeters for mobile fluoroscopes used for specific surgical
application.
(5) The written safety
procedures must provide precautionary measures to be adhered to during the use
of this device in addition to the procedures provided in
41.1(3)"a"(4).
g. Fluoroscopic timer.
(1) Means shall be provided to preset the
cumulative on-time of the fluoroscopic X-ray tube. The maximum cumulative time
of the timing device shall not exceed five minutes without resetting.
(2) A signal audible to the fluoroscopist
shall indicate the completion of any preset cumulative on-time. Such signal
shall continue to sound while X-rays are produced until the timing device is
reset.
h. Control of
scattered radiation.
(1) Fluoroscopic table
designs when combined with procedures utilized shall be such that no
unprotected part of any staff or ancillary individual's body shall be exposed
to unattenuated scattered radiation which originates from under the table. The
attenuation required shall be not less than 0.25 millimeter lead
equivalent.
(2) Equipment
configuration when combined with procedures shall be such that no portion of
any staff or ancillary individual's body, except the extremities, shall be
exposed to the unattenuated scattered radiation emanating from above the
tabletop unless that individual:
1. Is at
least 120 centimeters from the center of the useful beam, or
2. The radiation has passed through not less
than 0.25 millimeter lead equivalent material including, but not limited to,
drapes, Bucky-slot cover panel, or self-supporting curtains, in addition to any
lead equivalency provided by the protective apron referred to in
41.1(3)"a"(5).
(3) The agency may grant exemptions to
41.1(5)"h"(2) where a sterile field will not permit the use of
the normal protective barriers. Where the use of prefitted sterilized covers
for the barriers is practical, the agency shall not permit such
exemption.
i. Spot-film
exposure reproducibility. Fluoroscopic systems equipped with spot-film
(radiographic) mode shall meet the exposure reproducibility requirements of
41.1(6)"d" when operating in the spot-film mode.
j. Radiation therapy simulation systems.
Radiation therapy simulation systems shall be exempt from all the requirements
of 41.1(5)
"a," "c," "d," and
"g" provided
that:
(1) Such systems are designed and used
in such a manner that no individual other than the patient is in the X-ray room
during periods of time when the system is producing X-rays; and
(2) Systems which do not meet the
requirements of 41.1(5)"g" are provided with a means of
indicating the cumulative time that an individual patient has been exposed to
X-rays. Procedures shall require in such cases that the timer be reset between
examinations.
k.
Dose-area-product monitor requirements.
(1)
All fluoroscopic equipment installed after July 1, 2002, and used for special
procedures (e.g., pacemaker implantation, diagnostic cardiac procedures
(catheterization), and therapeutic cardiac procedures (angioplasty-balloon;
stent; directional coronary atherectomy; rotational atherectomy; laser
atherectomy; radio frequency ablation; and intravascular brachytherapy)) shall
be equipped with a dose-area-product monitor capable of recording the total
radiation dose received by a patient when the fluoroscopic tube is used.
Equipment used and installed prior to July 1, 2002, shall be retrofitted with
the radiation exposure device by January 1, 2004.
(2) Each facility using fluoroscopic
equipment for special procedures shall include in the patient's chart and in a
log for agency review the patient radiation exposure received per procedure.
Adult doses that exceed 300 rad and doses for children (under the age of 18)
that exceed 100 rad must be reviewed by the facility's radiation safety
committee. The review must document the reason why a dose exceeded 300 rad for
adults or 100 rad for children, and the reason must be documented in the
committee's minutes. If a facility does not have a radiation safety committee,
the facility must provide the agency, within 30 days of the event,
documentation stating why the patient's dose exceeded 300 rad for adults or 100
rad for children. Also, if the patient doses noted above are exceeded, the
patient's physician must do a follow-up examination of the patient to determine
if there is any evidence of dose recorded reaction and to ensure that proper
treatment is rendered.
(3) All
fluoroscopic radiation detection devices in this subrule shall be calibrated
annually or after repair or replacement.
l. Equipment operation.
(1) All imaging formed by the use of
fluoroscopic X-ray systems shall be directly viewed and interpreted by a
licensed practitioner of the healing arts.
(2) Overhead fluoroscopy shall not be used as
a positioning tool for general purpose radiographic examinations.
(3) Facilities that use fluoroscopic X-ray
systems shall maintain a record of cumulative fluoroscopic exposure time used
and the number of spot films for each examination. This record shall indicate
patient identification, type of examination, date of examination, and
operator's name.
m.
Additional requirements for stationary fluoroscopic systems used for cardiac
catheterization procedures.
(1) Protective
barriers shall be available for use by individuals whose presence is required
in the room during activation of the X-ray tube(s). If a protective barrier
includes or consists of a transparent viewing panel, the viewing panel shall
afford protection of not less than 0.5 millimeter of lead equivalent.
(2) Protective aprons of not less than 0.25
millimeter of lead equivalent shall be worn in the fluoroscopy room by all
individuals (except the patient). Any individual required to be in the room for
short periods of time may not be required to wear a protective apron if
exposure levels below minimum as seen on film badge reports can be verified.
Individuals not using protective aprons should follow ALARA by using time and
distance to reduce exposure. Any declared pregnant individual must meet the
requirements of 641-40.22
(136C).
n. Supervision of
fluoroscopy. The use of fluoroscopy by radiologic technologists and radiologic
students shall be performed under the direct supervision of a licensed
practitioner, a radiologist assistant or an advanced registered nurse
practitioner (ARNP), pursuant to 655-subrule 7.2(2), for the purpose of
localization to obtain images for diagnostic or therapeutic
purposes.
(6)
Radiographic systems other than fluoroscopic, dental intraoral,
veterinary, or computed tomography X-ray systems.
a. Beam limitation. The useful beam shall be
limited to the area of clinical interest. This shall be considered met if a
positive beam-limiting device meeting manufacturer's specifications and the
requirements of 41.1(6)
"h"(2) have been properly used or if
evidence of collimation is shown on at least three sides or three corners of
the film (for example, projections from the shutters of the collimator, cone
cutting at the corners, or borders at the film's edge.)
(1) General purpose stationary and mobile
X-ray systems and veterinarian systems (other than portable) installed after
July 1, 1998.
1. Only X-ray systems provided
with means for independent stepless adjustment of at least two dimensions of
the X-ray field shall be used.
2. A
method shall be provided for visually defining the perimeter of the X-ray
field.
* Illuminance shall be greater than 7.5 foot-candles or 80.3
LUX at 100 centimeters or maximum SID whichever is less.
* The total misalignment of the edges of the visually defined
field with the respective edges of the X-ray field along either the length or
width of the visually defined field shall not exceed 2 percent of the distance
from the source to the center of the visually defined field when the surface
upon which it appears is perpendicular to the axis of the X-ray beam.
3. The agency may grant an
exemption on noncertified X-ray systems to 41.1(6)"a"(1) "1"
and "2" provided the registrant makes a written application for such exemption
and in that application demonstrates it is impractical to comply with
41.1(6)"a"(1)"1" and "2"; and the purpose of
41.1(6)"a"(1)"1" and "2" will be met by other methods.
(2) Additional
requirements for stationary general purpose X-ray systems. In addition to the
requirements of 41.1(6)
"a"(1) , stationary general purpose
X-ray systems, both certified and noncertified, shall meet the following
requirements:
1. A method shall be provided to
indicate when the axis of the X-ray beam is perpendicular to the plane of the
image receptor, to align the center of the X-ray field with respect to the
center of the image receptor to within 2 percent of the SID, and to indicate
the SID to within 2 percent;
2. The
beam-limiting device shall indicate numerically the field size in the plane of
the image receptor to which it is adjusted; and
3. Indication of field size dimensions and
SIDs shall be specified in inches or centimeters, and shall be such that
aperture adjustments result in X-ray field dimensions in the plane of the image
receptor which correspond to those indicated by the beam-limiting device to
within 2 percent of the SID when the beam axis is indicated to be perpendicular
to the plane of the image receptor.
(3) X-ray systems designed for one image
receptor size. Radiographic equipment designed for only one image receptor size
at a fixed SID shall be provided with means to limit the field at the plane of
the image receptor to dimensions no greater than those of the image receptor,
and to align the center of the X-ray field with the center of the image
receptor to within 2 percent of the SID, or shall be provided with means to
both size and align the X-ray field such that the X-ray field at the plane of
the image receptor does not extend beyond any edge of the image
receptor.
(4) Reserved.
(5) X-ray systems other than those described
in 41.1(6)
"a"(1), (2), and (3), and veterinary systems
installed prior to July 1, 1998, and all portable veterinary X-ray systems.
1. Means shall be provided to limit the X-ray
field in the plane of the image receptor so that such field does not exceed
each dimension of the image receptor by more than 2 percent of the SID when the
axis of the X-ray beam is perpendicular to the plane of the image
receptor.
2. Means shall be
provided to align the center of the X-ray field with the center of the image
receptor to within 2 percent of the SID, or means shall be provided to both
size and align the X-ray field such that the X-ray field at the plane of the
image receptor does not extend beyond any edge of the image receptor.
Compliance shall be determined with the axis of the X-ray beam perpendicular to
the plane of the image receptor.
3.
41.1(6)
"a"(5)"1" and "2" may be met with a system that meets
the requirements for a general purpose X-ray system as specified in
41.1(6)
"a"(1) or, when alignment means are also provided, may
be met with either:
* An assortment of removable, fixed-aperture, beam-limiting
devices sufficient to meet the requirement for each combination of image
receptor size and SID for which the unit is designed with each such device
having clear and permanent markings to indicate the image receptor size and SID
for which it is designed; or
* A beam-limiting device having multiple fixed apertures
sufficient to meet the requirement for each combination of image receptor size
and SID for which the unit is designed. Permanent, clearly legible markings
shall indicate the image receptor size and SID for which each aperture is
designed and shall indicate which aperture is in position for use.
b. Radiation
exposure control devices.
(1) Timers.
1. Means shall be provided to initiate the
radiation exposure by a deliberate action on the part of the operator, such as
the depression of a switch. Radiation exposure shall not be initiated without
such an action.
2. Means shall be
provided to terminate the exposure at a preset time interval, preset product of
current and time, a preset number of pulses, or a preset radiation exposure to
the image receptor. In addition, it shall not be possible to make an exposure
when the timer is set to a "zero" or "off" position if either position is
provided. Except for dental panoramic systems, termination of an exposure shall
cause automatic resetting of the timer to its initial setting or to
"zero."
(2) X-ray
control.
1. Manual exposure control. An X-ray
control shall be incorporated into each X-ray system such that an exposure can
be terminated by the operator at any time except for exposure of one-half
second or less, or during serial radiography when means shall be provided to
permit completion of any single exposure of the series in process.
2. Each X-ray control shall be located in
such a way as to meet the following requirements: Stationary X-ray systems
(except podiatry and veterinary units) shall be required to have the X-ray
exposure switch permanently mounted in a protected area so that the operator is
required to remain in that protected area during the entire exposure and so
that the operator can view the patient while making any exposures; and mobile
and portable X-ray systems which are:
* Used for greater than one week in the same location, i.e., a
room or suite, shall meet the requirements of
41.1(6)"b"(2)"2"; or
* Used for greater than one hour and less than one week at the
same location, i.e., a room or suite, orin a clinical setting for routine
extremities only, or where moving the X-ray system from room to room is
impractical, shall meet the requirement of the above paragraph or be provided
with a 6.5 foot (1.98 m) high protective barrier which is placed at least 2.7
meters (9 feet) from the tube housing assembly. Written procedures must
instruct the operator to remain in the protected area during the entire
exposure. Stationary podiatric systems which do not meet the above requirements
shall be provided with a 9-foot exposure button cord which allows the operator
to remain behind a protective barrier during the entire exposure. If the
protective barrier is moveable, written procedures must be on file at the
facility, which dictate that the operator will remain behind the barrier during
the entire exposure.
3. The
X-ray control shall provide visual indication observable at or from the
operator's protected position whenever X-rays are produced. In addition, a
signal audible to the operator shall indicate that the exposure has
terminated.
(3) Automatic
exposure controls. When an automatic
exposure control is provided:
1. Indication shall be made on the control
panel when this mode of operation is selected;
2. If the X-ray tube potential is equal to or
greater than 50 kVp, the minimum exposure time for field emission equipment
rated for pulsed operation shall be equal to or less than a time interval
equivalent to 2 pulses;
3. The
minimum exposure time for all equipment other than that specified in
41.1(6)"b"(3)"2" shall be equal to or less than one-sixtieth
second or a time interval required to deliver 5 mAs, whichever is
greater;
4. Either the product of
peak X-ray tube potential, current, and exposure time shall be limited to not
more than 60 kWs per exposure, or the product of X-ray tube current and
exposure time shall be limited to not more than 600 mAs per exposure except
that, when the X-ray tube potential is less than 50 kVp, the product of X-ray
tube current and exposure time shall be limited to not more than 2000 mAs per
exposure; and
5. A visible signal
shall indicate when an exposure has been terminated at the limits required by
41.1(6)"b"(3)"4," and manual resetting shall be required
before further automatically timed exposures can be made.
(4) Reproducibility. With a timer setting of
0.5 seconds or less, the average exposure period (T) shall be greater than or
equal to five times the maximum exposure period (Tmax)
minus the minimum exposure period (Tmin) when four timer
tests are performed:
Click here
to view Image
(5)
Exposure duration (timer) linearity. For systems having independent selection
of exposure time settings, the average ratios (X1) of
exposure to the indicated timer setting, in units of C
kg-1s-1 (mR/s), obtained
at any two clinically used timer settings shall not differ by more than 0.10
times their sum. This is written as:
Click here
to view Image
where X1 and X2
are the average C
kg-1s-1(mR/s)
values.
c.
Source-to-skin distance. All mobile or portable radiographic systems shall be
provided with means to limit the source-to-skin distance to equal to or greater
than 30 centimeters except for veterinary systems.
d.
exposure
reproducibility. When all technique factors are held constant, including
control panel selections associated with automatic exposure control systems,
the coefficient of variation of exposure for both manual and automatic exposure
control systems shall not exceed 0.05. This requirement applies to clinically
used techniques.
e. Radiation from
capacitor energy storage equipment in standby status. Radiation emitted from
the X-ray tube when the system is fully charged and the exposure switch or
timer is not activated shall not exceed a rate of 2 milliroentgens (0.516
µC/kg) per hour at 5 centimeters from any accessible
surface of the diagnostic source assembly, with the beam-limiting device fully
open.
f. Accuracy. Deviation of
measured technique factors from indicated values of kVp and exposure time shall
not exceed the limits specified for that system by its manufacturer. In the
absence of manufacturer's specifications, the deviation shall not exceed 10
percent of the indicated value for kVp and 20 percent for time.
g. mA/mAs linearity. The following
requirements apply when the equipment is operated on a power supply as
specified by the manufacturer for any fixed X-ray tube potential within the
range of 40 percent to 100 percent of the maximum rated:
(1) Equipment having independent selection of
X-ray tube current (mA). The average ratios (Xi) of
exposure to the indicated milliampere-seconds product (C
kg-1mAs-1(or mR/mAs))
obtained at any two consecutive tube current settings shall not differ by more
than 0.10 times their sum:
Click here
to view Image
where X1 and X2
are the average values obtained at each of two consecutive tube current
settings, or at two settings differing by no more than a factor of 2 where the
tube current selection is continuous.
(2) Equipment having a combined X-ray tube
current-exposure time product (mAs) selector, but not a separate tube current
(mA) selector. The average ratios (Xi) of exposure to
the indicated milliampere-seconds product, in units of mR/mAs (or C
kg-1mAs-1), obtained at
any two consecutive mAs selector settings shall not differ by more than 0.10
times their sum:
Click here
to view Image
where X1 and X2
are the average values obtained at any two consecutive mAs selector settings,
or at two settings differing by no more than a factor of 2 where the mAs
selector provides continuous selection.
(3) Measuring compliance. Determination of
compliance shall be based on 10 exposures taken within a time period of one
hour, at each of the two settings. These two settings may include any two focal
spot sizes except where one is equal to or less than 0.45 millimeters and the
other is greater than 0.45 millimeters. For purposes of this requirement, focal
spot size is the nominal focal spot size specified by the X-ray tube
manufacturer.
h.
Additional requirements applicable to certified systems only. Diagnostic X-ray
systems incorporating one or more certified component(s) shall be required to
comply with the following additional requirement(s) which relate to that
certified component(s).
(1) Beam limitation
for stationary and mobile general purpose X-ray systems.
1. There shall be provided a means of
stepless adjustment of the X-ray field. The minimum field size at an SID of 100
centimeters shall be equal to or less than 5 centimeters by 5
centimeters.
2. When a light
localizer is used to define the X-ray field, it shall provide an average
illumination of not less than 160 lux or 15 foot-candles at 100 centimeters or
at the maximum SID, whichever is less. The average illumination shall be based
upon measurements made in the approximate center of each quadrant of the light
field. Radiation therapy simulation systems manufactured on and after May 27,
1980, are exempt from this requirement.
3. The edge of the light field at 100
centimeters or at the maximum SID, whichever is less, shall have a contrast
ratio, corrected for ambient lighting, of not less than 4 in the case of
beam-limiting devices designed for use on stationary equipment, and a contrast
ratio of not less than 3 in the case of beam-limiting devices designed for use
on mobile equipment. The contrast ratio is defined as
I1/I2 where
I1 is the illumination 3 millimeters from the edge of
the light field toward the center of the field; and I2
is the illumination 3 millimeters from the edge of the light field away from
the center of the field. Compliance shall be determined with a measuring
instrument aperture of 1 millimeter in diameter.
(2) Beam limitation and alignment on
stationary general purpose X-ray systems equipped with PBL. If PBL is being
used, the following requirements shall be met:
1. PBL shall prevent the production of X-rays
when
* Either the length or width of the X-ray field in the plane of
the image receptor differs, except as permitted by
41.1(6)"h"(3), from the corresponding image receptor
dimensions by more than 3 percent of the SID; or
* The sum of the length and width differences as stated in
41.1(6)"h"(2)"1" above without regard to sign exceeds 4
percent of the SID;
2.
Compliance with 41.1(6)"h"(2)"1" shall be determined when the
equipment indicates that the beam axis is perpendicular to the plane of the
image receptor. Compliance shall be determined no sooner than 5 seconds after
insertion of the image receptor;
3.
The PBL system shall be capable of operation, at the discretion of the
operator, such that the size of the field may be made smaller than the size of
the image receptor through stepless adjustment of the field size. The minimum
field size at an SID of 100 centimeters shall be equal to or less than 5
centimeters by 5 centimeters;
4.
The PBL system shall be designed such that if a change in image receptor does
not cause an automatic return to PBL function as described in
41.1(6)"h"(2)"1," then any change of image receptor size or
SID must cause the automatic return.
(3) Beam limitation for portable X-ray
systems. Beam limitation for portable X-ray systems shall meet the beam
limitation requirements of 41.1(6)"a" or
41.1(6)"h"(2).
i. Tube stands for portable X-ray systems. A
tube stand or other mechanical support shall be used for portable X-ray
systems, so that the X-ray tube housing assembly need not be handheld during
exposures.
j. Systems used in a
clinical (nonsurgical) setting shall be restricted to one room within a
location or suite which meets the requirements of 41.1(3)"d."
(7)
Intraoral
dental radiographic systems. In addition to the provisions of 41.1(3)
and 41.1(4), the requirements of 41.1(7) apply to X-ray equipment and
associated facilities used for dental radiography. Requirements for extraoral
dental radiographic systems are covered in 41.1(6). Only systems meeting the
requirements of 41.1(7) shall be used. Additional requirements specific to
handheld dental X-ray equipment are outlined in 41.1(7)"i."
a.
Source-to-skin distance.
X-ray systems designed for use with an intraoral image receptor shall be
provided with means to limit source-to-skin distance to not less than:
(1) 18 centimeters if operable above 50 kVp,
or
(2) 10 centimeters if not
operable above 50 kVp.
b.
Beam limitation. Radiographic systems designed for use with an
intraoral image receptor shall be provided with means to limit the X-ray beam
such that:
(1) If the minimum source-to-skin
distance (SSD) is 18 centimeters or more, the X-ray field, at the minimum SSD,
shall be containable in a circle having a diameter of no more than 7
centimeters; and
(2) If the minimum
SSD is less than 18 centimeters, the X-ray field, at the minimum SSD, shall be
containable in a circle having a diameter of no more than 6
centimeters.
(3) The position
indicating device shall be shielded and open-ended. The shielding shall be
equivalent to the requirements of
41.1(4)"c."
c.
Exposure control.
(1) Exposure initiation.
1. Means shall be provided to initiate the
radiation exposure by a deliberate action on the part of the operator, such as
the depression of a switch. Radiation exposure shall not be initiated without
such an action; and
2. It shall not
be possible to make an exposure when the timer is set to a "zero" or "off"
position if either position is provided.
(2) Exposure indication. Means shall be
provided for visual indication observable at or from the operator's protected
position whenever X-rays are produced. In addition, a signal audible to the
operator shall indicate that the exposure has terminated except in X-ray
systems that cannot be altered to meet this requirement.
(3) Exposure termination.
1. Means shall be provided to terminate the
exposure at a preset time interval, preset product of current and time, a
preset number of pulses, or a preset radiation exposure to the image receptor.
In addition:
2. Termination of
exposure shall cause automatic resetting of the timer to its initial setting or
to "zero."
3. An X-ray control
shall be incorporated into each X-ray system such that an exposure can be
terminated by the operator at any time, except for exposures of one-half
(½) second or less.
(4) Exposure duration (timer) linearity. For
systems having independent selection of exposure time settings, the average
ratios (X1) of exposure to the indicated timer setting,
in units of C
kg-2s-1(mR/s), obtained
at any two clinically used timer settings shall not differ by more than 0.10
times their sum. This is written as:
Click here
to view Image
where X1 and X2
are the average values.
(5)
Each X-ray exposure switch shall be located in such a way as to meet the
following requirements:
1. Stationary X-ray
systems shall be required to have the X-ray exposure switch located in a
protected area or have an exposure switch cord of sufficient length to permit
the operator to activate the equipment while in a protected area, e.g.,
corridor outside the operatory. The procedures required under
41.1(3)"a"(4) must instruct the operator to remain in the
protected area during the entire exposure.
2. Mobile and portable X-ray systems which
are:
* Used for greater than one week in the same location, i.e., a
room or suite, shall meet the requirements of
41.1(7)"c"(5)"1."
* Used for greater than one hour and less than one week at the
same location, i.e., a room or suite, shall meet the requirements of the above
paragraph or be provided with a 6.5 foot (1.98 m) high protective barrier or
means to allow the operator to be at least 6 feet ( 1.8 meters) from the tube
housing assembly while making exposure.
3. Portable dental X-ray systems designed
with a backscatter shield may be used without an additional protective barrier,
but the operator must stand directly behind the equipment to allow the shield
to function as designed.
d.
Reproducibility. When the
equipment is operated on an adequate power supply as specified by the
manufacturer, the estimated coefficient of variation of radiation
exposures shall be no greater than 0.05, for any
specific combination of selected technique factors.
e.
mA/mS linearity. The
following requirements apply when the equipment is operated on a power supply
as specified by the manufacturer for any fixed X-ray tube potential within the
range of 40 percent to 100 percent of the maximum rated.
(1) Equipment having independent selection of
X-ray tube current (mA). The average ratios (X1) of
exposure to the indicated milliampere-seconds product, in units of C
kg-1mAs-1 (or mR/mAs),
obtained at any two consecutive tube current settings shall not differ by more
than 0.10 times their sum:
Click here
to view Image
where X1 and X2
are the average values obtained at each of two consecutive tube current
settings, or at two settings differing by no more than a factor of 2 where the
tube current selection is continuous.
(2) Equipment having a combined X-ray tube
current-exposure time product (mAs) selector, but not a separate tube current
(mA) selector. The average ratios (X1) of exposure to
the indicated milliampere-seconds product, in units of C
kg-1mAs-1(or mR/mAs),
obtained at any two consecutive mAs selector settings shall not differ by more
than 0.10 times their sum:
Click here
to view Image
where X1 and X2
are the average values obtained at any two mAs selector settings, or at two
settings differing by no more than a factor of 2 where the mAs selector
provides continuous selection.
(3) Measuring compliance. Determination of
compliance shall be based on 10 exposures taken within a time period of one
hour, at each of the two settings. These two settings may include any two focal
spot sizes except where one is equal to or less than 0.45 millimeters and the
other is greater than 0.45 millimeters. For purposes of this requirement, focal
spot size is the nominal focal spot size specified by the X-ray tube
manufacturer.
f.
Accuracy. Deviation of technique factors from indicated values
for kVp and exposure time (if time is independently selectable) shall not
exceed the limits specified for that system by its manufacturer. In the absence
of manufacturer's specifications the deviation shall not exceed 10 percent of
the indicated value for kVp and 20 percent for time.
g.
kVp limitations. Dental
X-ray machine with a nominal fixed kVp of less than 50 kVp shall not be used to
make diagnostic dental radiographs of humans.
h.
Administrative controls.
(1) Patient and film holding devices shall be
used when the techniques permit.
(2) The tube housing and the PID for
stationary or mobile systems shall not be held by the operator during an
exposure.
(3) The X-ray system
shall be operated in such a manner that the useful beam at the patient's skin
does not exceed the requirements of 41.1(7)"b"(1).
(4) Dental fluoroscopy without image
intensification shall not be used.
i.
Handheld dental X-ray
systems. Only equipment specifically designed by the manufacturer to
be held by the operator for intraoral dental X-ray exposures is allowed to be
operated pursuant to this subrule.
(1)
Operators shall be specifically trained to operate the equipment. Records of
training shall be kept at the facility until the operator is no longer an
employee or until the equipment is removed from the facility.
(2) Protective aprons of not less than 0.25
millimeter lead equivalent shall be provided for operators to wear while
operating the equipment.
(3)
Dosimetry shall be provided for operators who are expected to exceed 10 percent
of the annual occupational dose limit as outlined in
641-40.84 (136C).
(4) Operators shall operate the equipment
according to the manufacturer's instructions.
(5) The image receptor used must be digital
radiography (DR), computed radiography (CR), or intraoral film with a speed
class designated as "E/F" or a film with a faster speed designation than "F" or
"E/F."
(6) No individual except the
equipment operator may be within a radius of at least 6 feet from the patient
during exposures.
(7) The equipment
shall not be operated unless the backscatter shield is in place as designed by
the manufacturer.
(8) The equipment
shall not be operated in hallways, waiting rooms, or other areas where access
for individuals of the general public cannot be controlled.
(9) The equipment shall be held without any
motion during a patient examination. If the operator has difficulty in holding
the equipment stationary, the operator shall use a tube stand. The equipment
shall be operated on a tube stand whenever practicable to avoid unnecessary
motion and retakes.
(10) When not
in use, the equipment shall be stored in a manner that would prevent
inadvertent exposures or use by unauthorized individuals.
(9)
Bone densitometry units.
a. No additional shielding for the room is
required.
b. Film badges, OSL
devices, or TLDs must be issued for the first six months to all personnel
operating the unit. If monitoring indicates no exposure, the IDPH may allow
discontinuance of monitoring upon written request. When new procedures are
started that have not been previously monitored, monitoring must be reinstated
for six months and another request for discontinuance submitted to the
agency.
c. Reserved.
d. Specific operating procedures must be
prepared and made available at the operator's position.
e. Bone densitometry on human patients shall
be conducted only under a prescription of a licensed physician, a licensed
physician assistant as defined in Iowa Code section
148C.1, subsection 6,
or a licensed registered nurse who is registered as an advanced registered
nurse practitioner pursuant to Iowa Code chapter 152.
f. During the operation of the bone
densitometry system:
(1) The operator,
ancillary personnel, and members of the general public shall be positioned at
least one meter from the patient and bone densitometry system during the
examination.
(2) The operator shall
advise the patient that the bone densitometry examination is a type of X-ray
procedure.
g. Equipment
shall be maintained and operated in accordance with the manufacturer's
specifications. Records of maintenance shall be kept for inspection by the
agency.
(11)
Computed tomography
X-ray systems.
a. Definitions. In
addition to the definitions provided in
641-38.2 (136C),
641-40.2 (136C), and 41.1(2),
the following definitions shall be applicable to 41.1(11):
"Computed tomography dose index" means the
integral from "7T to +7T of the dose profile along a line perpendicular to the
tomographic plane divided by the product of the nominal tomographic section
thickness and the number of tomograms produced in a single scan, that
is:
Click here
to view Image
where:
z =Position along a line perpendicular to the tomographic
plane.
D(z)= Dose at position z.
T = Nominal tomographic section thickness.
n =Number of tomograms produced in a single scan.
This definition assumes that the dose profile is centered
around z = 0 and that, for a multiple tomogram system, the scan increment
between adjacent scans is nT.
"Contrast scale" means the change in the
linear attenuation coefficient per CTN relative to water, that is:
Click here
to view Image
where:
µx = Linear attenuation
coefficient of the material of interest.
µw= Linear attenuation coefficient of water.
CTNx = of the
material of interest.
CTNw = of water.
"CS" (see "Contrast scale").
"CT conditions of operation" means all
selectable parameters governing the operation of a CT X-ray system including,
but not limited to, nominal tomographic section thickness, filtration, and the
technique factors as defined in 41.1(2).
"CTDI" (see "Computed tomography dose
index").
"CT gantry" means the tube housing assemblies,
beam-limiting devices, detectors, and the supporting structures and frames
which hold these components.
"CTN" (see "CT number").
"CT number" means the number used to represent
the X-ray attenuation associated with each elemental area of the CT
image.
Click here
to view Image
where:
k = A constant. (The constant has a normal value of 1,000 when
the Houndsfield scale of CTN is used.)
µx = Linear attenuation
coefficient of the material of interest.
µw = Linear attenuation
coefficient of water.
"Dose profile" means the dose as a function of
position along a line.
"Elemental area" means the smallest area
within a tomogram for which the X-ray attenuation properties of a body are
depicted (see also "Picture element").
"Multiple tomogram system" means a computed
tomography X-ray system which obtains X-ray transmission data simultaneously
during a single scan to produce more than one tomogram.
"Noise" means the standard deviation of the
fluctuation in CTN expressed as a percentage of the attenuation coefficient of
water. Its estimate (Ss) is calculated using the
following expression:
Click here
to view Image
where:
CS = Linear attenuation coefficient of the material of
interest.
µw = Linear attenuation
coefficient of water.
s = Estimated standard deviation of the CTN of picture elements
in a specified area of the CT image.
"Nominal tomographic section thickness" means
the full width at half-maximum of the sensitivity profile taken at the center
of the cross-sectional volume over which X-ray transmission data are
collected.
"Picture element" means an elemental area of a
tomogram.
"Reference plane" means a plane which is
displaced from and parallel to the tomographic plane.
"Scan" means the complete process of
collecting X-ray transmission data for the production of a tomogram. Data can
be collected simultaneously during a single scan for the production of one or
more tomograms.
"Scan increment" means the amount of relative
displacement of the patient with respect to the CT X-ray system between
successive scans measured along the direction of such displacement.
"Scan sequence" means a preselected set of two
or more scans performed consecutively under preselected CT conditions of
operation.
"Scan time" means the period of time between
the beginning and end of X-ray transmission data accumulation for a single
scan.
"Single tomogram system" means a CT X-ray
system which obtains X-ray transmission data during a scan to produce a single
tomogram.
"Tomographic plane" means that geometric plane
which is identified as corresponding to the output tomogram.
"Tomographic section" means the volume of an
object whose X-ray attenuation properties are imaged in a tomogram.
b. Requirements for equipment.
(1) Termination of exposure.
1. Means shall be provided to terminate the
X-ray exposure automatically by either deenergizing the X-ray source or
shuttering the X-ray beam in the event of equipment failure affecting data
collection. Such termination shall occur within an interval that limits the
total scan time to no more than 110 percent of its preset value through the use
of either a backup timer or devices which monitor equipment function.
2. A visible signal shall indicate when the
X-ray exposure has been terminated through the means required by
41.1(11)"b"(1)"1."
3. The operator shall be able to terminate
the X-ray exposure at any time during a scan, or series of scans under CT X-ray
system control, of greater than one-half second duration.
(2) Tomographic plane indication and
alignment.
1. For any single tomogram system,
means shall be provided to permit visual determination of the tomographic plane
or a reference plane offset from the tomographic plane.
2. For any multiple tomogram system, means
shall be provided to permit visual determination of the location of a reference
plane. This reference plane can be offset from the location of the tomographic
planes.
3. If a device using a
light source is used to satisfy 41.1(11)"b"(2)"1" or "2," the
light source shall provide illumination levels sufficient to permit visual
determination of the location of the tomographic plane or reference plane under
ambient light conditions of up to 500 lux.
(3) Beam-on and shutter status indicators and
control switches.
1. The CT X-ray control and
gantry shall provide visual indication whenever X-rays are produced and, if
applicable, whether the shutter is open or closed.
2. Each emergency button or switch shall be
clearly labeled as to its function.
(4) Indication of CT conditions of operation.
The CT X-ray system shall be designed such that the CT conditions of operation
to be used during a scan or a scan sequence shall be indicated prior to the
initiation of a scan or a scan sequence. On equipment having all or some of
these conditions of operation at fixed values, this requirement may be met by
permanent markings. Indication of CT conditions of operation shall be visible
from any position from which scan initiation is possible.
(5) Extraneous radiation. When data are not
being collected for image production, the radiation adjacent to the tube port
shall not exceed that permitted by 41.1(4)"c."
(6) Maximum surface CTDI identification. The
angular position where the maximum surface CTDI occurs shall be identified to
allow for reproducible positioning of a CT dosimetry phantom.
(7) Additional requirements applicable to CT
X-ray systems containing a gantry manufactured after September 3, 1985.
1. The total error in the indicated location
of the tomographic plane or reference plane shall not exceed 5
millimeters.
2. If the X-ray
production period is less than one-half second, the indication of X-ray
production shall be actuated for at least one-half second. Indicators at or
near the gantry shall be discernible from any point external to the patient
opening where insertion of any part of the human body into the primary beam is
possible.
3. The deviation of
indicated scan increment versus actual increment shall not exceed plus or minus
1 millimeter with any mass from 0 to 100 kilograms resting on the support
device. The patient support device shall be incremented from a typical starting
position to the maximum incremented distance or 30 centimeters, whichever is
less, and then returned to the starting position. Measurement of actual versus
indicated scan increment may be taken anywhere along this travel.
4. Premature termination of the X-ray
exposure by the operator shall necessitate resetting of the CT conditions of
operation prior to the initiation of another scan.
c. Facility design requirements.
(1) Aural communication. Provision shall be
made for two-way aural communication between the patient and the operator at
the control panel.
(2) Viewing
systems.
1. Windows, mirrors, closed-circuit
television, or an equivalent shall be provided to permit continuous observation
of the patient during irradiation and shall be so located that the operator can
observe the patient from the control panel.
2. When the primary viewing system is by
electronic means, an alternate viewing system (which may be electronic) shall
be available for use in the event of failure of the primary viewing
system.
d.
Surveys, calibrations, spot checks, and operating procedures.
(1) Surveys.
1. All CT X-ray systems shall have a survey
made by, or under the direction of, a qualified expert. In addition, such
surveys shall be done after any change in the facility or equipment which might
cause a significant increase in radiation hazard.
2. The registrant shall obtain a written
report of the survey from the qualified expert, and a copy of the report shall
be made available to the agency upon request.
(2) Radiation calibrations.
1. The calibration of the radiation output of
the CT X-ray system shall be performed by, or under the direction of, a
qualified expert who is physically present at the facility during such
calibration.
2. The calibration of
a CT X-ray system shall be performed at intervals specified by a qualified
expert and after any change or replacement of components which, in the opinion
of the qualified expert, could cause a change in the radiation
output.
3. The calibration of the
radiation output of a CT X-ray system shall be performed with a calibrated
dosimetry system. The calibration of such system shall be traceable to a
national standard. The dosimetry system shall have been calibrated within the
preceding two years.
4. CT
dosimetry phantom(s) shall be used in determining the radiation output of a CT
X-ray system. Such phantom(s) shall meet the following specifications and
conditions of use: CT dosimetry phantom(s) shall be right circular cylinders of
polymethyl methacrylate of density 1.19 plus or minus 0.01 grams per cubic
centimeter. The phantom(s) shall be at least 14 centimeters in length and shall
have diameters of 32.0 centimeters for testing CT X-ray systems designed to
image any section of the body and 16.0 centimeters for systems designed to
image the head or for whole body scanners operated in the head scanning mode;
CT dosimetry phantom(s) shall provide means for the placement of a dosimeter(s)
along the axis of rotation and along a line parallel to the axis of rotation
1.0 centimeter from the outer surface and within the phantom. Means for the
placement of dosimeters or alignment devices at other locations may be
provided; any effects on the doses measured due to the removal of phantom
material to accommodate dosimeters shall be accounted for through appropriate
corrections to the reported data or included in the statement of maximum
deviation for the values obtained using the phantom; and all dose measurements
shall be performed with the CT dosimetry phantom placed on the patient couch or
support device without additional attenuation materials present.
5. The calibration shall be required for each
type of head, body, or whole-body scan performed at the facility.
6. Calibration shall meet the following
requirements: The dose profile along the center axis of the CT dosimetry
phantom for the minimum, maximum, and midrange values of the nominal
tomographic section thickness used by the registrant shall be measurable. Where
less than three nominal tomographic thicknesses can be selected, the dose
profile determination shall be performed for each available nominal tomographic
section thickness; the
CTDI3/ along the two axes
specified in 41.1(11)"d"(2)"4" shall be measured. (For the
purpose of determining the CTDI, the manufacturer's statement as to the nominal
tomographic section thickness for that particular system may be utilized.) The
CT dosimetry phantom shall be oriented so that the measurement point 1.0
centimeter from the outer surface and within the phantom is in the same angular
position within the gantry as the point of maximum surface CTDI identified. The
CT conditions of operation shall correspond to typical values used by the
registrant; and the spot checks specified in 41.1(11)"d"(3)
shall be made.
7. Calibration
procedures shall be in writing. Records of calibrations performed shall be
maintained for inspection by the agency.
(3) Spot checks.
1. The spot-check procedures shall be in
writing and shall have been developed by a qualified expert.
2. The spot-check procedures shall
incorporate the use of a CT dosimetry phantom which has a capability of
providing an indication of contrast scale, noise, nominal tomographic section
thickness, the resolution capability of the system for low and high contrast
objects, and measuring the mean CTN for water or other reference
material.
3. All spot checks shall
be included in the calibration required by 41.1(11)"d"(2) and
at time intervals and under system conditions specified by a qualified
expert.
4. Spot checks shall
include acquisition of images obtained with the CT dosimetry phantom(s) using
the same processing mode and CT conditions of operation as are used to perform
calibrations required by 41.1(11)"d"(2). The images shall be
retained, until a new calibration is performed, in two forms as follows:
photographic copies of the images obtained from the image display device; and
images stored in digital form on a storage medium compatible with the CT X-ray
system.
5. Written records of the
spot checks performed shall be maintained for inspection by the
agency.
(4) Operating
procedures.
1. The CT X-ray system shall not
be operated except by a licensed practitioner or an individual who has been
specifically trained in its operation and holds a current permit to practice as
a general radiologic technologist as defined under the provisions of
641-Chapter 42.
