Code of Massachusetts Regulations
105 CMR - DEPARTMENT OF PUBLIC HEALTH
Title 105 CMR 120.000 - The Control of Radiation
RECORDKEEPING REQUIREMENTS
Section 120.406 - Diagnostic X-ray Systems

Universal Citation: 105 CMR 120.000 MA Code of Regs 120.406

Current through Register 1531, September 27, 2024

(A) Beam Limitation Except for Mammographic Systems. The useful beam shall be limited to the area of clinical interest. This shall be deemed to have been met if a positive beam limiting device meeting manufacturer's specifications and the requirements of 105 CMR 120.406(G)(2) has 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, Including Veterinary Systems (Other than Portable) Installed After December 31, 1997.
(a) Only x-ray systems provided with a means for independent stepless adjustment of at least two dimensions of the x-ray field shall be used;

(b) A method shall be provided for visually defining the perimeter of the x-ray field. 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% 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;

(c) The Agency may grant an exemption on non-certified x-ray systems to 105 CMR 120.406(A)(1)(a); and,

(d) Provided the registrant makes a written application for such exemption and in that application:
1. Demonstrates it is impractical to comply with 105 CMR 120.406(A)(1)(a) and (b); and,

2. The purpose of 105 CMR 120.406(A)(1)(a) and (b) will be met by other methods.

(2) Additional Requirements for Stationary General Purpose X-ray Systems. In addition to the requirements of 105 CMR 120.406, all stationary general purpose x-ray systems, both certified and non-certified shall meet the following requirements:
(a) 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 two percent of the SID, and to indicate the SID to within 2%;

(b) The beam-limiting device shall indicate numerically the field size in the plane of the image receptor to which it is adjusted; and,

(c) Indication of field size dimensions and SID's shall be specified in inches and/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% 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% 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) Radiographic Systems Other Than Those Designated in 105 CMR 120.406(A)(1) through (3).
(a) 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% of the SID when the axis of the x-ray beam is perpendicular to the plane of the image receptor.

(b) Means shall be provided to align the center of the x-ray field with the center of the image receptor to within 2% 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.

(c)105 CMR 120.406(A)(4)(a) and (b) may be met with a system that meets the requirements for a general purpose x-ray system as specified in 105 CMR 120.406(A)(1) or, when alignment means are also provided, may be met with either:
1. 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,

2. 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.

(1) Timers. 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. In addition, it shall not be possible to initiate 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.

(3) Exposure Termination. 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. Except for dental panoramic systems, termination of an exposure shall cause automatic resetting of the timer to its initial setting or to "zero."
(a) 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:

1. Exposure 1/2 of second or less; or,

2. During serial radiography when means shall be provided to permit completion of any single exposure of the series in process.

(b) 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 two pulses;

3. The minimum exposure time for all equipment other than that specified in 105 CMR 120.406(B)(3)(b)2. shall be equal to or less than 1/60 second or a time interval required to deliver five 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 105 CMR 120.406(B)(3)(b)4., and manual resetting shall be required before further automatically timed exposures can be made.

(4) Exposure Duration (Timer) Linearity. For systems having independent selection of exposure time settings, the average ratios (Xi) 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:

(X1 - X2) <= 0.1 (X1 + X2)

where X1 and X2 are the average C kg-1s-1 (mR/s) values.

(5) Exposure Control Location. The x-ray exposure control shall be so placed that the operator can view the patient while making any exposure.

(6) Operator Protection, Except Veterinary Systems.
(a) Stationary Systems. Stationary x-ray systems shall be required to have the x-ray control permanently mounted in a protected area so that the operator is required to remain in that protected area during the entire exposure.

(b) Mobile and Portable Systems. Mobile and portable x-ray systems which are:
1. Used continuously for greater than one week in the same location, i.e., a room or suite, shall meet the requirements of 105 CMR 120.406(B)(6)(a);

2. Used for less than one week at the same location shall be provided with either a protective barrier at least 6.5 feet (two m) high for operator protection during exposure, or means shall be provided to allow the operator to be at least nine feet (2.7 m) from the tube housing assembly during the 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.

(7) Exposure Reproducibility. When all techniques factors are held constant, including control panel selections associated with 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.

(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) Radiation from Capacitor Energy Storage Equipment in Standby Status. Radiation emitted from the x-ray tube when the exposure switch or timer is not activated shall not exceed a rate of two milliroentgen (0.516 µC/kg) per hour at five centimeters from any accessible surface of the diagnostic source assembly, with the beam-limiting device fully open.

(E) 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% of the indicated value for kVp and 20% for time.

(F) 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% to 100% of the maximum rated:

(1) Equipment Having Independent Selection of X-ray Tube Current (mA). The average ratios (Xi) of air kerma to the indicated milliampere-seconds product (C kg-1 mAs-1 (or mR/mAs)) obtained at any two consecutive tube current settings shall not differ by more than 0.10 times their sum:

X1-X2 <= 0.10 (X1+X2)

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 two where the tube current selection is continuous.

(2) Equipment Having a Combined X-ray Tube Current-exposure Time Product (mAs) Selector. The average ratios (Xi) of air kerma to the indicated milliampere-seconds product, in units of C kg-1 mAs-1 (or mR/mAs), obtained at any two consecutive mAs selector settings shall not differ by more than 0.10 times their sum:

X1-X2 <= 0.10 (X1 +X2)

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 two where the mAs selector provides continuous selection.

(3) Measuring Compliance. Determination of compliance shall be based on three 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.

(G) 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 Portable X-ray Systems. Beam limitation for portable x-ray systems shall meet the beam limitation requirements of 105 CMR 120.406(A)(1).

(2) Field Limitation and Alignment on Stationary General Purpose X-ray Systems. For stationary, general purpose x-ray systems which contain a tube housing assembly, an x-ray control, and, for those systems so equipped, a table, all certified in accordance with 21 CFR 1020.30(C):
(a) Means shall be provided for positive beam limitation which will, at the SID for which the device is designed, either cause automatic adjustment of the x-ray field in the plane of the image receptor to the image receptor size within five seconds after insertion of the image receptor or, if adjustment is accomplished automatically in a time interval greater than five seconds or is manual, will prevent production of x-rays until such adjustment is completed. For the SID at which the device is not intended to operate, the device shall prevent the production of x-rays.

(b) The x-ray field size in the plane of the image receptor, whether automatically or manually adjusted, shall be such that neither the length nor the width of the x-ray field differs from that of the image receptor by greater than 2% of the SID and that the sum of the length and width differences without regard to sign be no greater than 3% of the SID when the equipment indicates that the beam axis is perpendicular to the plane of the image receptor.

(c) The radiographic system shall be capable of operation, at the discretion of the operator, such that the field size at the image receptor can be adjusted to a size smaller than the image receptor. The minimum field size at a distance of 100 centimeters shall be equal to or less than five by five centimeters. Return to positive beam limitation as specified in 105 CMR 120.406(F)(6)(a) and (b) shall occur upon a change in image receptor.

(d) Positive beam limitation may be bypassed when radiography is conducted which does not use the cassette tray or permanently mounted vertical cassette holder, or when either the beam axis or table angulation is not within 10° of the horizontal or vertical during any part of the exposure, or during stereoscopic radiography. If the bypass mode is provided, return to positive beam limitation shall be automatic.

(e) A capability may be provided for overriding positive beam limitation in the event of system failure or to perform special procedures which cannot be performed in the positive mode. If so provided, a key shall be required to override the positive mode It shall be impossible to remove the key while the positive mode is overridden.

(3) Timers. Except for dental panoramic systems, termination of exposure shall cause automatic resetting of the timer to its initial setting or to "zero."

(4) Transmission Limit for Image Receptor Supporting Devices Used for Mammography. For x-ray systems manufactured after September 5, 1978 which are designed only for mammography, the transmission of the primary beam through any image receptor support provided with the system shall be limited such that the Exposure five centimeters from any accessible surface beyond the plane of the image receptor supporting device does not exceed 0.1 milliroentgen (25.8 C/kg) for each activation of the tube. Exposure shall be measured with the system operated at the minimum SID for which it is designed. Compliance shall be determined at the maximum rated peak tube potential for the system and at the maximum rated product of tube current and exposure time (mAs) for that peak tube potential. Compliance shall be determined by measurements averaged over an area of 100 square centimeters with no linear dimension greater than 20 centimeters.

(H) Any facility that utilizes a CR or DR system shall follow the manufacturer's recommendations for Quality Assurance and Quality Control.

(1) All Quality Control tests and results shall be documented.

(2) Quality assurance and quality control records shall be maintained for a minimum of 24 months and readily available for review by representatives of the Department.

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