Chapter DHS 157

DHS 157.75(3)(b) (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.

DHS 157.75(3)(c) (c) For all other diagnostic source assemblies, the maximum-rated peak tube potential and the maximum-rated continuous tube current for the maximum-rated peak tube potential.

DHS 157.75(4) (4) Radiation from components other than the diagnostic source assembly. The radiation emitted by a component other than the diagnostic source assembly may not exceed 20mGy (2.15 milliroentgens) 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.

DHS 157.75(5) (5) Beam quality.

DHS 157.75(5)(a) (a) The half-value layer of the useful beam for a given x-ray tube potential may not be less than the values shown in Table DHS 157.75. If it is necessary to determine the half-value layer at an x-ray tube potential that is not listed in Table DHS 157.75, linear interpolation or extrapolation may be made.

- See PDF for table

DHS 157.75(5)(b) (b) For x-ray systems using capacitor discharge to provide power to an x-ray tube, half-value layer shall be determined with the system fully charged and a setting of 10 mAs for each exposure.

DHS 157.75(5)(c) (c) The required minimal half-value layer of the useful beam shall include the filtration contributed by all materials that are permanently between the source and the patient.

DHS 157.75(5)(d) (d) For x-ray systems with variable filtration controls, the system shall prevent an exposure unless the appropriate filtration is in place for the kilovolts peak selected.

DHS 157.75(6) (6) Multiple tubes. When 2 or more radiographic tubes are controlled by one exposure switch, the tube that has been selected shall be clearly indicated prior to initiation of the exposure. The indication shall be both on an x-ray control panel and at or near the selected tube housing assembly.

DHS 157.75(7) (7) 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 an x-ray system.

DHS 157.75(8) (8) Technique indicators.

DHS 157.75(8)(a) (a) 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.

DHS 157.75(8)(b) (b) The requirement in par. (a) 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.

DHS 157.75(9) (9) Maintaining compliance. Diagnostic x-ray systems and their associated components used on humans and certified under the federal x-ray equipment performance standard, 21 CFR 1020, shall be maintained in compliance with applicable requirements of that standard.

DHS 157.75(10) (10) Locks. All position locking, holding and centering devices on x-ray system components and systems shall function as intended.

DHS 157.75 History History: CR 01-108: cr. Register July 2002 No. 559, eff. 8-1-02; CR 06-021: am. Table Register October 2006 No. 610, eff. 11-1-06; CR 22-015: am. Table Register June 2023 No. 810, eff. 7-1-23.

DHS 157.76 DHS 157.76 Fluoroscopic equipment. Only image-intensified or direct-digital receptor fluoroscopic equipment shall be used for fluoroscopy. Equipment for fluoroscopic imaging or for recording images from the fluoroscopic image receptor, except computed tomography x-ray systems manufactured on or after November 29, 1984, shall meet all the following requirements:

DHS 157.76(1) (1) Limitation of useful beam.

DHS 157.76(1)(a) (a) The fluoroscopic imaging assembly shall be provided with a primary protective barrier which intercepts the entire cross section of the useful beam at any source to image distance. The x-ray tube used for fluoroscopy shall not produce x-rays unless the barrier is in position to intercept the entire useful beam. The air kerma rate due to transmission through the barrier with the attenuation block in the useful beam combined with radiation from the fluoroscopic image receptor shall not exceed 3.34 x 10-3 percent of the entrance air kerma rate, at a distance of 10 cm from any accessible surface of the fluoroscopic imaging assembly beyond the plane of the image receptor.

DHS 157.76(1)(b) (b) Compliance shall be determined as follows:

DHS 157.76(1)(b)1. 1. The air kerma rate shall be measured as required under sub. (4). The air kerma rate due to transmission through the primary barrier combined with radiation from the fluoroscopic image receptor shall be determined by measurements averaged over an area of 100 square cm with no linear dimension greater than 20 cm.

DHS 157.76(1)(b)2. 2. If the source is below the tabletop, the measurement shall be made with the input surface of the fluoroscopic imaging assembly positioned 30 cm above the tabletop. If the source is above the tabletop and the source to image distance 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 cm.

DHS 157.76(1)(b)3. 3. Movable grids and compression devices shall be removed from the useful beam during the measurement.

DHS 157.76(1)(b)4. 4. For all measurements, the attenuation block shall be positioned in the useful beam 10 cm from the point of measurement of entrance air kerma rate and between this point and the input surface of the fluoroscopic imaging assembly.

DHS 157.76(1)(c) (c) Radiation therapy simulation systems shall be exempt from this requirement provided the systems are intended only for remote control operation and the manufacturer sets forth instructions for assemblers with respect to control location as part of the information required in 21 CFR 1020.30 (g).

DHS 157.76(2) (2) Field limitation.

DHS 157.76(2)(a) (a) For fluoroscopic equipment manufactured after February 25, 1978, when the angle between the image receptor and the beam axis of the x-ray beam 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. Compliance with par. (e) 1. and 2. shall be determined with the beam axis indicated to be perpendicular to the plane of the image receptor.

DHS 157.76(2)(b) (b) Means shall be provided to permit further limitation of the x-ray field to sizes smaller than the limits of par. (e) 1. and 2. Beam limiting devices manufactured after May 22, 1979, and incorporated in equipment with a variable source to image distance, the capability of a visible area of greater than 300 square cm, or both, shall be provided with means for stepless adjustment of the x-ray field. Equipment with a fixed source to image distance and the capability of a visible area of no greater than 300 square cm shall be provided with either stepless adjustment of the x-ray field or with a means to further limit the x-ray field size at the plane of the image receptor to 125 square cm or less. Stepless adjustment shall, at the greatest source to image distance, provide continuous field sizes from the maximum obtainable to a field size containable in a square of 5 cm by 5 cm. This paragraph does not apply to intensified fluoroscopy units without image intensification.

DHS 157.76(2)(c) (c) The x-ray field produced by non-image-intensified fluoroscopic equipment shall not extend beyond the entire visible area of the image receptor. Means shall be provided for stepless adjustment of field size. The minimum field size, at the greatest source to image distance, shall be containable in a square of 5 cm by 5 cm.

DHS 157.76(2)(d) (d) For fluoroscopic equipment with inherently circular image receptors manufactured before June 10, 2006, other than radiation therapy simulation systems, all the following applies:

DHS 157.76(2)(d)1. 1. 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% of the source to image distance. The sum of the excess length and the excess width shall be no greater than 4% of the source to image distance.

DHS 157.76(2)(d)2. 2. For rectangular 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.

DHS 157.76(2)(e) (e) For fluoroscopic equipment manufactured on or after June 10, 2006, other than radiation therapy simulation systems, the maximum area of the x-ray field in the plane of the image receptor shall conform to one of the following requirements:

DHS 157.76(2)(e)1. 1. When any linear dimension of the visible area of the image receptor measured through the center of the visible area is less than or equal to 34 cm in any direction, at least 80% of the area of the x-ray field overlaps the visible area of the image receptor.

DHS 157.76(2)(e)2. 2. When any linear dimension of the visible area of the image receptor measured through the center of the visible area is greater than 34 cm in any direction, the x-ray field measured along the direction of greatest misalignment with the visible area of the image receptor does not extend beyond the edge of the visible area of the image receptor by more than 2 cm.

DHS 157.76(2)(f) (f) For x-ray systems with inherently rectangular image receptors manufactured on or after June 10, 2006, all the following applies:

DHS 157.76(2)(f)1. 1. 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% of the source to image distance. The sum of the excess length and the excess width shall be no greater than 4% of the source to image distance.

DHS 157.76(2)(f)2. 2. 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.

DHS 157.76(2)(g) (g) If the fluoroscopic x-ray field size is adjusted automatically as the source to image distance or image receptor size is changed, a capability may be provided for overriding the automatic adjustment in case of system failure. If it is so provided, a signal visible at the fluoroscopist’s position shall indicate whenever the automatic field adjustment is overridden. Each such system failure override switch shall be clearly labeled as follows:

For X-ray Field Limitation System Failure

DHS 157.76(3) (3) Activation of tube. X-ray production in the fluoroscopic mode shall be controlled by a device which requires continuous pressure by the operator for the entire time of any exposure. When recording serial radiographic images from the fluoroscopic image receptor, the operator shall be able to terminate the x-ray exposure at any time, but means may be provided to permit completion of any single exposure of the series in process.

DHS 157.76(4) (4) Air kerma rates.

DHS 157.76(4)(a) (a) Fluoroscopic equipment manufactured before May 19, 1995 shall meet all the following requirements:

DHS 157.76(4)(a)1. 1. Equipment provided with automatic exposure rate control shall not be operable at any combination of tube potential and current that will result in an air kerma rate in excess of 88 mGy per minute (10 R/min) at the measurement point specified in par. (e), except as specified in par. (e) 6.

DHS 157.76(4)(a)2. 2. Equipment provided without automatic exposure rate control shall not be operable at any combination of tube potential and current that will result in an air kerma rate in excess of 44 mGy per minute (5 R/min) at the measurement point specified in par. (e), except as specified in par. (e) 6.

DHS 157.76(4)(a)3. 3. Equipment provided with both an automatic exposure rate control mode and a manual mode shall not be operable at any combination of tube potential and current that will result in an air kerma rate in excess of 88 mGy per minute (10 R/min) in either mode at the measurement point specified in par. (e), except as specified in par. (e) 6.

DHS 157.76(4)(a)4. 4. Equipment may be modified in accordance with 21 CFR 1020.30(q) to comply with par. (a). When the equipment is modified, it shall bear a label indicating the date of the modification and the statement:

Modified to comply with 21 CFR 1020.32 (h) (2).

DHS 157.76(4)(b) (b) The requirements of par. (a) do not apply to all the following:

DHS 157.76(4)(b)1. 1. During recording of fluoroscopic images.

DHS 157.76(4)(b)2. 2. When a mode of operation has an optional high-level control, in which case that mode shall not be operable at any combination of tube potential and current that will result in an air kerma rate in excess of the rates specified in this subsection at the measurement point specified in par. (e), unless the high-level control is activated. Special means of activation of high-level controls shall be required. The high-level control shall be operable only 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.

DHS 157.76(4)(c) (c) Fluoroscopic equipment manufactured on or after May 19, 1995 shall meet all the following requirements:

DHS 157.76(4)(c)1. 1. Equipped with automatic exposure rate control if operable at any combination of tube potential and current that results in an air kerma rate greater than 44 mGy per minute (5 R/min) at the measurement point specified in this subsection. Provision for manual selection of technique factors may be provided.

DHS 157.76(4)(c)2. 2. Not be operable at any combination of tube potential and current that will result in an air kerma rate in excess of 88 mGy per minute (10 R/min) at the measurement point specified in par. (e)

DHS 157.76(4)(d) (d) The requirements of par. (c) do not apply to all the following:

DHS 157.76(4)(d)1. 1. For equipment manufactured prior to June 10, 2006, during the recording of images from a fluoroscopic image receptor using photographic film or a video camera when the x-ray source is operated in a pulsed mode.

DHS 157.76(4)(d)2. 2. For equipment manufactured on or after June 10, 2006, during the recording of images from the fluoroscopic image receptor for the purpose of providing the user with a recorded image after termination of exposure. Such recording does not include images resulting from a last image-hold feature that are not recorded.

DHS 157.76(4)(d)3. 3. When a mode of operation has an optional high-level control and the control is activated, in which case the equipment shall not be operable at any combination of tube potential and current that will result in an air kerma rate in excess of 176 mGy per minute (20 R/min) at the measurement point specified par. (e). Special means of activation of high-level controls shall be required. The high-level control shall be operable only 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.

DHS 157.76(4)(e) (e) Compliance with par. (c) shall be determined as follows:

DHS 157.76(4)(e)1. 1. If the source is below the x-ray table, the air kerma rate shall be measured at 1 cm above the tabletop or cradle.

DHS 157.76(4)(e)2. 2. If the source is above the x-ray table, the air kerma rate shall be measured at 30 cm above the tabletop with the end of the beam-limiting device or spacer positioned as closely as possible to the point of measurement.

DHS 157.76(4)(e)3. 3. In a C-arm type of fluoroscope, the air kerma rate shall be measured at 30 cm from the input surface of the fluoroscopic imaging assembly, with the source positioned at any available source to image distance, provided that the end of the beam limiting device or spacer is no closer than 30 cm from the input surface of the fluoroscopic imaging assembly.

DHS 157.76(4)(e)4. 4. In a C-arm type of fluoroscope having an source to image distance less than 45 cm, the air kerma rate shall be measured at the minimum source to skin distance.

DHS 157.76(4)(e)5. 5. In a lateral type of fluoroscope, the air kerma rate shall be measured at a point 15 cm 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 cm to the centerline of the x-ray table.

DHS 157.76(4)(e)6. 6. Fluoroscopic radiation therapy simulation systems are exempt from this paragraph.

DHS 157.76(5) (5) Indication of potential and current. During fluoroscopy and cinefluorography, x-ray tube potential and current shall be continuously indicated. Deviation of x-ray tube potential and current from the indicated values shall not exceed the maximum deviation as stated by the manufacturer in accordance with 21 CFR 1020.30 (h) (3).

DHS 157.76(6) (6) Source to skin distance.

DHS 157.76(6)(a) (a) Means shall be provided to limit the source to skin distance to not less than 38 cm on stationary fluoroscopes and to not less than 30 cm on mobile and portable fluoroscopes. In addition, for fluoroscopes intended for specific surgical application that would be prohibited at the source-skin distances specified in this paragraph, provisions may be made for operation at shorter source-skin distances but in no case less than 20 cm.

DHS 157.76(6)(b) (b) For stationary, mobile, or portable C-arm fluoroscopic systems manufactured on or after June 10, 2006, having a maximum source-image receptor distance of less than 45 cm, means shall be provided to limit the source-skin distance to not less than 19 cm. Such systems shall be labeled for extremity use only. In addition, for those systems intended for specific surgical application that would be prohibited at the source-skin distances specified in this paragraph, provisions may be made for operation at shorter source-skin distances but in no case less than 10 cm.

DHS 157.76(7) (7) Fluoroscopic irradiation time, display, and signal.

DHS 157.76(7)(a) (a) Fluoroscopic equipment manufactured before June 10, 2006, shall be provided with means to preset the cumulative irradiation time of the fluoroscopic tube. The maximum cumulative time of the timing device shall not exceed 5 minutes without resetting. A signal audible to the fluoroscopist shall indicate the completion of any preset cumulative Irradiation time. Such signal shall continue to sound while x-rays are produced until the timing device is reset.

DHS 157.76(7)(b) (b) As an alternative to the requirements of par. (a), radiation therapy simulation systems may be provided with a means to indicate the total cumulative exposure time during which x-rays were produced, and which is capable of being reset between x-ray examinations.

DHS 157.76(7)(c) (c) For x-ray controls manufactured on or after June 10, 2006, all of the following shall be provided for each fluoroscopic tube:

DHS 157.76(7)(c)1. 1. A display of the fluoroscopic irradiation time at the fluoroscopist’s working position.

DHS 157.76(7)(c)2. 2. The display required in subd. 1. shall function independently of the audible signal described in par. (a) and meet all the following requirements:

DHS 157.76(7)(c)2.a. a. When the x-ray tube is activated, the fluoroscopic irradiation time in minutes and tenths of minutes shall be continuously displayed and updated at least once every 6 seconds.

DHS 157.76(7)(c)2.b. b. The fluoroscopic irradiation time shall also be displayed within 6 seconds of termination of an exposure and remain displayed until reset.

DHS 157.76(7)(c)2.c. c. Means shall be provided to reset the display to zero prior to the beginning of a new examination or procedure.

DHS 157.76(7)(c)3. 3. A signal audible to the fluoroscopist shall sound for each passage of 5 minutes of fluoroscopic irradiation time during an examination or procedure. The signal shall sound until manually reset or, if automatically reset, for at least 2 seconds.

DHS 157.76(7)(d) (d) If fluoroscopic equipment is modified in accordance with 21 CFR 1020.30(q) to comply with the requirements in par. (a), it shall bear a label that states:

Modified to comply with 21 CFR 1020.32(h)(2)

DHS 157.76(8) (8) Mobile and portable fluoroscopes. Mobile and portable fluoroscopes shall use image-intensification or a direct-digital receptor.

DHS 157.76(9) (9) Display of last-image-hold.

DHS 157.76(9)(a) (a) Fluoroscopic equipment manufactured on or after June 10, 2006, shall be equipped with means to display the last image following termination of the fluoroscopic exposure.

DHS 157.76(9)(b) (b) For an LIH obtained by retaining pre-termination fluoroscopic images, if the number of images and method of combining images are selectable by the user, the selection shall be indicated prior to initiation of the fluoroscopic exposure.

DHS 157.76(9)(c) (c) For an LIH image obtained by initiating a separate radiographic-like exposure at the termination of fluoroscopic imaging, the technique factors for the LIH image shall be selectable prior to the fluoroscopic exposure, and the combination selected shall be indicated prior to initiation of the fluoroscopic exposure.

DHS 157.76(9)(d) (d) Means shall be provided to clearly indicate to the user whether a displayed image is the LIH radiograph or fluoroscopy. Display of the LIH radiograph shall be replaced by the fluoroscopic image concurrently with re-initiation of fluoroscopic exposure, unless separate displays are provided for the LIH radiograph and fluoroscopic images.

DHS 157.76(9)(e) (e) The predetermined or selectable options for producing the LIH radiograph shall be described in the information required by 21 CFR 1020.30 (h). The information shall include a description of any technique factors applicable for the selected option and the impact of the selectable options on image characteristics and the magnitude of radiation emissions.