New Mexico Administrative Code
Title 20 - ENVIRONMENTAL PROTECTION
Chapter 3 - RADIATION PROTECTION
Part 6 - X-RAYS IN HEALING ARTS
Section 20.3.6.7 - DEFINITIONS

A. "Accessible surface" means the external surface of the enclosure or housing provided by the manufacturer.

B. "Added filter" means the filter added to the inherent filtration.

C. "Aluminum equivalent" means the thickness of aluminum (type 1100 alloy) affording the same attenuation, under specified conditions as the material in question. (The nominal chemical composition of type 1100 aluminum alloy is 99.00 percent minimum aluminum, 0.12 percent copper.)

D. "Attenuation block" means a block or stack 3.8 cm thick of type 1100 aluminum alloy or other material having equivalent attenuation.

E. "Automatic exposure control" 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").

F. "Barrier" (see "Protective barrier").

G. "Beam axis" means a line from the source through the center of the x-ray field.

H. "Beam-limiting device" means a device which provides a means to restrict the dimensions of the x-ray field.

I. "Changeable filter" means any filter, exclusive of inherent filtration, which can be removed from the useful beam through any electronic, mechanical or physical process.

J. "Coefficient of variation (SA)" means the ratio of the standard deviation to the mean value of a population of observations. It is estimated using the following equation:

where:

x = mean value of observations in sample

xi = ith observation in sample

N = number of observations in sample

K. "Collimator" means a device or mechanism by which the x-ray beam is restricted in size.

L. "Contact therapy system" means that the x-ray tube port is put in contact with, or within 5 centimeters of, the surface being treated.

M. "Control panel" means that part of the x-ray control upon which are mounted the switches, knobs, pushbuttons, and other hardware necessary for manually setting the technique factors.

N. "Cooling curve" means the graphical relationship between heat units stored and cooling time.

O. "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.

P. "Density (D)" (as used in conjunction with image receptors) means the logarithm to the base 10 of the ratio of the incident to the transmitted luminous flux, where I is luminous flux.

D=LOG SUB 10 [{I~Incident} over {I~Transmitted}]

Q. "Diagnostic source assembly" means the tube housing assembly with a beam-limiting device attached.

R. "Diagnostic x-ray system" means an x-ray system designed for irradiation of any part of the human body for the purpose of diagnosis or visualization.

S. "Direct scattered radiation" means that scattered radiation which has been deviated in direction only by materials irradiated by the useful beam (see also "Scattered radiation").

T. "Entrance exposure rate" means the roentgens per unit time at the point where the center of the useful beam enters the patient.

U. "Equipment" (see "X-ray equipment").

V. "Exposure" means the quotient of dQ by dm where dQ is the absolute value of the total charge of the ions of one sign produced in air when all the electrons (negatrons and positrons) liberated by photons in a volume element of air having mass dm are completely stopped in air. (The special unit of exposure is the roentgen, 1R = 2.58 x 10-4 C/Kg)

W. "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.

X. "Filter" means material placed in the useful beam to absorb preferentially the less penetrating components.

Y. "Fluoroscopic imaging assembly" means a component which comprises a reception system in which x-ray photons produce a fluoroscopic image. It includes equipment housings, electrical interlocks if any, the primary protective barrier, and structural material providing linkage between the image receptor and the diagnostic source assembly.

Z. "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.

AA. "Gonad shield" means a protective barrier for the testes or ovaries.

AB. "Half-value layer (HVL)" means the thickness of specified material which attenuates the beam of radiation to an extent such that the exposure rate is reduced to one-half of its original value. In this definition the contribution of all scattered radiation, other than any which might be present initially in the beam concerned, is deemed to be excluded.

AC. "Image intensifier" means a device which produces an image of greater contrast than would be produced without the device present.

AD. "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.

AE. "Inherent filtration" means filtration permanently in the useful beam; it includes the window of the x-ray tube and any permanent tube or source enclosure.

AF. "Interlock" means a device for precluding access to a radiation area by automatically terminating exposure upon entry by personnel.

AG. "Kilovolts peak (kVp)" (see "Peak tube potential").

AH. "kWs" means kilowatt second which is equal to the product of peak kilovolts, amperes, and seconds or 103 kVmA sec.

AI. "Lead equivalent" means the thickness of material in question affording the same attenuation, under specified conditions, as the lead in question.

AJ. "Leakage radiation" means radiation emanating from the diagnostic or therapeutic source assembly except for:

AK. "Leakage technique factors" means the technique factors associated with the tube housing assembly which are used in measuring leakage radiation. They are defined as follows:

AL. "Light field" means that area of the intersection of the light beam from the beam-limiting device and 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 illumination is one-fourth of the maximum in the intersection.

AM. "Line pair" means an object in which parallel wires or strips are placed so that the space between each wire or strip is equal to the width of the wire or strip. A line pair is one space and a strip or wire.

AN. "Linear Accelerator" means a device for accelerating particles employing alternate electrodes and gaps arranged in a straight line, so proportioned that when their potentials are varied in the proper amplitude and frequency, particles passing through them receive successive increments of energy.

AO. "Line-voltage regulation" means the difference between the no-load and the load potentials expressed as a percent of the load line potential, that is: Percent line-voltage regulation = 100 (Vn-V1)/V1 where:

AP. "Maximum line current" means the root mean square current in the supply line of an x-ray machine operating at its maximum rating.

AQ. "Mobile equipment" (see "X-ray equipment").

AR. "Peak tube potential" means the maximum value of the potential difference across the x-ray tube during an exposure.

AS. "Personal monitoring" means the estimation of dose to a person.

AT. "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 devices(s) is part of an electronic circuit which controls the duration of time the tube is activated (see also "Automatic exposure control").

AU. "Portable equipment" (see "X-ray equipment").

AV. "Position indicating device (PID)" 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.

AW. "Primary protective barrier" (see "Protective barrier").

AX. "Protective apron" means an apron made of radiation absorbing materials, used to reduce radiation exposure.

AY. "Protective barrier" means a barrier of radiation absorbing material(s) used to reduce radiation exposure. The types of protective barriers are as follows:

AZ. "Protective glove" means a glove made of radiation absorbing materials used to reduce radiation exposure.

BA. "Qualified expert" (see 106.CC [Subsection CC. Of Section 7 of 20.3.1.7 NMAC]).

BB. "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.

BC. "Radiographic imaging system" means any system whereby a permanent or semi-permanent image is recorded on an image receptor by the action of ionizing radiation.

BD. "Recording" means producing a permanent form of an image resulting from x-ray photons (e.g., film, video tape).

BE. "Registrant", as used in this Subpart [Part], means any person who owns or possesses and administratively controls an x-ray system which is used to deliberately expose humans or animals to the useful beam of the system and is required by the provisions in Subpart 1 and 2 [Part 1 and 2] of these regulations to register with this Department.

BF. "Repair person (Service person)" means an individual who maintains an x-ray system; not limited to a manufacturer, assembler or user.

BG. "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.

BH. Scattered radiation" means radiation that, during passage through matter, has been deviated in direction (see also "Direct scattered radiation").

BI. "Secondary protective barrier (see "Protective barrier").

BJ. "SID" (see "Source-image receptor distance").

BK. "Source" means the focal spot of the x-ray tube.

BL. "Source-image receptor distance (SID)" means the distance from the source to the center of the input surface of the image receptor.

BM. "Spot film" means a radiograph which is made during a fluoroscopic examination to permanently record conditions which exist during that fluoroscopic procedure.

BN. "Stationary equipment " (see "X-ray equipment").

BO. "Stray radiation" means the sum of leakage and scattered radiation.

BP. "Technique factors" means the conditions of operation. They are specified as follows:

BQ. "Therapeutic-type protective tube housing" means the tube housing with tube installed and it includes high voltage or filament transformers and other appropriate elements when they are contained within that housing.

BR. "Tube" means an x-ray tube, unless otherwise specified.

BS. "Tube housing assembly" means the tube housing with tube installed. It includes high-voltage or filament transformers and other appropriate elements when they are contained within the tube housing.

BT. "Tube rating chart" means the set of curves which specify the rated limits of operation of the tube in terms of the technique factors.

BU. "Useful beam" means the radiation which passes through the tube housing port and the aperture of the beam-limiting device when the exposure switch or timer is activated.

BV. "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.

BW. "Visible area" means that portion of the input surface of the image receptor over which incident x-ray photons produce a visible image.

BX. "X-ray control" means a device which controls input power to the x-ray high-voltage generator of the x-ray tube. It includes equipment which controls the technique factors of an x-ray exposure.

BY. "X-ray equipment" means an x-ray system, subsystem or component thereof. Types of x-ray equipment are as follows:

BZ. "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.

CA. "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.

CB. "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.

CC. "X-ray subsystem" means any combination of two or more components of an x-ray system for which there are requirements specified in this Subpart [Part].

CD. "X-ray tube" means any electron tube which is designed for the conversion of electrical energy into x-ray energy.