D.C. Mun. Regs. tit. 22, r. 22-B10854
The provisions of this section apply to equipment for radiography, except equipment for fluoroscopic imaging or for recording images from the fluoroscopic image receptor, or computed tomography x-ray systems manufactured on or after November 29, 1984.
The technique factors to be used during an exposure shall be indicated before the exposure begins, except when automatic exposure controls are used, in which case the technique factors which are set prior to the exposure shall be indicated. On equipment having fixed technique factors, this requirement may be met by permanent markings. Indication of technique factors shall be visible from the operator's position except in the case of spot films made by the fluoroscopist.
Means shall be provided to terminate the exposure at a preset time interval, a preset product of current and time, a preset number of pulses, or a preset radiation exposure to the image receptor.
Except during serial radiography, the operator shall be able to terminate the exposure at any time during an exposure of greater than one-half (1/2) second. Except during panoramic dental radiography, termination of exposure shall cause automatic resetting of the timer to its initial setting or to zero (0). It shall not be possible to make an exposure when the timer is set to a zero (0) or off position if either position is provided.
During serial radiography, the operator 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.
When an automatic exposure control is provided:
Deviation of technique factors from indicated values shall not exceed the limits given in the information provided in accordance with § 10853.17.
The following requirements shall apply when the equipment is operated on an adequate power supply as specified by the manufacturer in accordance with the requirements of § 10853.17.
For any specific combination of selected technique factors, the estimated coefficient of variation of the air kerma shall be no greater than five hundredths (0.05).
Determination of compliance shall be based on ten (10) consecutive measurements taken within a time period of one (1) hour. Equipment manufactured after September 5, 1978, shall be subject to the additional requirement that all variable controls for technique factors shall be adjusted to alternate settings and reset to the test setting after each measurement. The percent line-voltage regulation shall be determined for each measurement. All values for percent line-voltage regulation shall be within plus or minus one (+/- 1) of the mean value for all measurements. For equipment having automatic exposure controls, compliance shall be determined with a sufficient thickness of attenuating material in the useful beam such that the technique factors can be adjusted to provide individual exposures of a minimum of twelve (12) pulses on field emission equipment rated for pulsed operation or no less than one-tenth (0.10) second per exposure on all other equipment.
The following requirements apply when the equipment is operated on a power supply as specified by the manufacturer in accordance with the requirements of § 10853.17 for any fixed x-ray tube potential within the range of forty percent (40%) to one hundred percent (100%) of the maximum rated.
The average ratios of air kerma to the indicated milliampere-seconds product (mGy/mAs) obtained at any two consecutive tube current settings shall not differ by more than one tenth (0.10) times their sum. This is: X[1] - X[2] </= 0.10(X[1] + X[2]); where X[1] and X[2] are the average mGy/mAs values obtained at each of two (2) consecutive milliampere-seconds selector settings or at two (2) settings differing by no more than a factor of two (2) where the milliampere-seconds selector provides continuous selection.
For equipment manufactured after May 3, 1994, the average ratios of air kerma to the indicated milliampere-seconds product (mGy/mAs) obtained at any two (2) consecutive mAs selector settings shall not differ by more than one tenth (0.10) times their sum. This is: X[1] - X[2] </= 0.10 (X[1] + X[2]); where X[1] and X[2] are the average mGy/mAs values obtained at each of two (2) consecutive milliampere-seconds elector settings or at two (2) settings differing by no more than a factor of two (2) where the milliampere seconds selector provides continuous selection.
Determination of compliance will be based on ten (10) exposures, made within one (1) hour, at each of the two (2) settings. These two (2) settings may include any two (2) focal spot sizes except where one (1) is equal to or less than forty-five hundredths millimeter (0.45 mm) and the other is greater than forty-five hundredths millimeter (0.45 mm). For purposes of this requirement, focal spot size is the focal spot size specified by the x-ray tube manufacturer. The percent line-voltage regulation shall be determined for each measurement. All values for percent line-voltage regulation at any one (10) combination of technique factors shall be within plus or minus one (1) of the mean value for all measurements at these technique factors.
Except when spot-film devices are in service, mobile, portable, and stationary general purpose radiographic x-ray systems shall meet the following requirements:
Except when spot-film devices are in service, stationary general purpose x-ray systems shall meet the following requirements in addition to those prescribed in § 10854.16:
Equipment for use with intraoral image receptors. Radiographic equipment designed for use with an intraoral image receptor shall be provided with means to limit the x-ray beam such that:
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 two percent (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.
Radiographic systems designed only for mammography and general purpose radiography systems, when special attachments for mammography are in service, manufactured on or after November 1, 1977, and before September 30, 1999, shall be provided with means to limit the useful beam such that the x-ray field at the plane of the image receptor does not extend beyond any edge of the image receptor at any designated SID except the edge of the image receptor designed to be adjacent to the chest wall where the x-ray field may not extend beyond this edge by more than two percent (2%) of the SID. This requirement can be met with a system that performs as prescribed in § 10854.23(a), (b), and (c). When the beam-limiting device and image receptor support device are designed to be used to immobilize the breast during a mammographic procedure and the SID may vary, the SID indication specified in § 10854.23(b) and (c) shall be the maximum SID for which the beam-limiting device or aperture is designed.
Mammographic beam-limiting devices manufactured on or after September 30, 1999, shall be provided with a means to limit the useful beam such that the x-ray field at the plane of the image receptor does not extend beyond any edge of the image receptor by more than two percent (2%) of the SID. This requirement can be met with a system that performs as prescribed in § 10854.23(a), (b), and (c). For systems that allow changes in the SID, the SID indication specified in § 10854.23(b) and (c) shall be the maximum SID for which the beam-limiting device or aperture is designed.
Each image receptor support device manufactured on or after November 1, 1977, intended for installation on a system designed for mammography shall have clear and permanent markings to indicate the maximum image receptor size for which it is designed.
Radiographic systems not specifically covered in § 10854.16, 10854.17, 10854.23(b), 10854.23(c), and 10854.31, and systems covered in Paragraph (a), which are also designed for use with extraoral image receptors and when used with an extraoral image receptor, shall be provided with means 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 two percent (2%) of the SID, when the axis of the x-ray beam is perpendicular to the plane of the image receptor. In addition, means shall be provided to align the center of the x-ray field with the center of the image receptor to within two percent (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. These requirements may be met with:
The requirements of this section shall apply to radiographic systems which contain positive bean limitation (PBL).
When a PBL system is provided, it shall prevent x-ray production when:
When provided, the PBL system shall function as described in § 10854.25 whenever all the following conditions are met:
Compliance with the requirements of § 10854.25 shall be determined when the equipment indicates that the beam axis is perpendicular to the plane of the image receptor and the provisions of § 10854.26 are met. Compliance shall be determined no sooner than five (5) seconds after insertion of the image receptor.
The PBL system shall be capable of operation such that, at the discretion of the operator, the size of the field may be made smaller than the size of the image receptor through stepless adjustment of the field size. Each dimension of the minimum field size at an SID of one hundred centimeters (100 cm) shall be equal to or less than five centimeters (5 cm). Return to PBL function as described in § 10854.25 shall occur automatically upon any change of image receptor size or SID.
A capability may be provided for overriding PBL in case of system failure and for servicing the system. This override may be for all SIDs and image receptor sizes. A key shall be required for any override capability that is accessible to the operator. It shall not be possible to remove the key while PBL is overridden. Each such key switch or key shall be clearly and durably labeled as follows:
"For X-ray Field Limitation System Failure".
The override capability is considered accessible to the operator if it is referenced in the operator's manual or in other material intended for the operator or if its location is such that the operator would consider it part of the operational controls.
The following requirements shall apply to spot-film devices, except when the spot-film device is provided for use with a radiation therapy simulation system:
A capability may be provided for overriding the automatic x-ray field size adjustment in case of system failure. If it is so provided, a signal visible at the fluoroscopist's position shall indicate whenever the automatic x-ray field size adjustment override is engaged. Each such system failure override switch shall be clearly labeled as follows:
"For X-ray Field Limitation System Failure".
X-ray systems designed for use with an intraoral image receptor shall be provided with means to limit the source-skin distance to not less than:
Mobile and portable x-ray systems other than dental shall be provided with means to limit the source-skin distance to not less than thirty centimeters (30 cm).
The x-ray control shall provide visual indication whenever x-rays are produced. In addition, a signal audible to the operator shall indicate that the exposure has terminated.
Where two or more radiographic tubes are controlled by one exposure switch, the tube or tubes which have been selected shall be clearly indicated before initiation of the exposure. This indication shall be both on the x-ray control and at or near the tube housing assembly which has been selected.
Radiation emitted from the x-ray tube shall not exceed:
For x-ray systems manufactured after September 5, 1978, and before September 30, 1999, 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 air kerma five centimeters (5 cm) from any accessible surface beyond the plane of the image receptor supporting device does not exceed eighty-eight hundredths microgray (0.88 mGy) (vice 0.1 mR exposure) for each activation of the tube.
For mammographic x-ray systems manufactured on or after September 30, 1999:
Compliance with the requirements of § 10854.37 and 10854.38(c) for transmission shall be determined with the x-ray system operated at the minimum SID for which it is designed, at the maximum rated peak tube potential, at the maximum rated product of x-ray tube current and exposure time (mAs) for the maximum rated peak tube potential, and by measurements averaged over an area of one hundred square centimeters (100 cm2) with no linear dimension greater than twenty centimeters (20 cm). The sensitive volume of the radiation measuring instrument shall not be positioned beyond the edge of the primary protective barrier along the chest wall side.
D.C. Mun. Regs. tit. 22, r. 22-B10854