DHS 157.77(5)(b)(b) An air kerma of 0.88 mGy (100mr/exposure) in one hour at 100 centimeters from the x-ray source, with the beam-limiting device fully open, when the system is discharged through the x-ray tube either manually or automatically by use of a discharge switch or deactivation of the input power. Compliance shall be determined by measurements of the maximum air kerma per discharge multiplied by the total number of discharges in one hour (duty cycle). The measurements shall be averaged over an area of 100 square centimeters with no linear dimension greater than 20 centimeters.

DHS 157.77(6)(6) Accuracy. Deviation of measured technique factors from indicated values of kVp and exposure time may not exceed the limits specified for that system by its manufacturer. In the absence of manufacturer’s specifications, the deviation may not exceed 10% of the indicated value for kVp and 10% of the time limit.

DHS 157.77(7)(7) mA/mAs linearity. X-ray equipment that 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 shall meet all the following requirements:

DHS 157.77(7)(a)(a) Equipment having independent selection of x-ray tube current (mA). The average ratios of exposure to the indicated milliampere-seconds product obtained at any 2 consecutive tube current settings may not differ by more than 0.10 times their sum:

where X1 and X2 are the average values obtained at any of 2 consecutive tube current settings or at 2 settings differing by no more than a factor of 2 where the tube current selection is continuous.

DHS 157.77(7)(b)(b) Equipment having a combined x-ray tube current-exposure time product selector, but not a separate tube current selector. The average ratios of exposure to the indicated milliampere-seconds product, in units of .001 mGy/mAs (mR/mAs), obtained at any 2 consecutive mAs selector settings may not differ by more than 0.10 times their sum:

where X1 and X2 are the average values obtained at any 2 consecutive mAs selector settings, or at 2 settings differing by no more than a factor of 2 where the mAs selector provides continuous selection.

DHS 157.77(7)(c)(c) Measuring compliance. Determination of compliance shall be based on 10 exposures taken within a time period of one hour at each of the 2 settings. These 2 settings may include any 2 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 an x-ray tube manufacturer.

DHS 157.77(8)(8) Additional requirements applicable to certified systems only. A diagnostic x-ray system incorporating one or more certified components shall meet all of the following additional requirements that relate to that certified component or components:

DHS 157.77(8)(a)(a) Beam limitation for stationary and mobile general purpose x-ray systems. Stationary and mobile general purpose x-ray systems shall meet all the following beam limitation requirements:

DHS 157.77(8)(a)1.1. There shall be provided a means of stepless adjustment of the size of the x-ray field. The minimum field size at a SID of 100 centimeters shall be equal to or less than 5 centimeters by 5 centimeters.

DHS 157.77(8)(a)2.2. When a light localizer type of collimator is used to define the x-ray field, it shall provide an average illumination of not less than 160 lux or 15 footcandles 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.

DHS 157.77(8)(a)3.3. 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 one millimeter in diameter.

DHS 157.77(8)(b)(b) Beam limitation and alignment on stationary general purpose x-ray systems equipped with PBL. If PBL is being used, the x-ray system shall meet all of the following requirements:

DHS 157.77(8)(b)1.1. PBL shall prevent the production of x-rays when either one of the following occurs:

DHS 157.77(8)(b)1.a.a. The length or width of the x-ray field in the plane of the image receptor differs, except as permitted by manual override, from the corresponding image receptor dimensions by more than 3% of the SID.

DHS 157.77(8)(b)1.b.b. The sum of the length and width differences, without regard to positive or negative mathematical sign, exceeds 4% of the SID.

DHS 157.77(8)(b)2.2. Compliance for exposure lock-out 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 more than 5 seconds after insertion of the image receptor.

DHS 157.77(8)(b)3.3. 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 adjustment of the field size. The minimum field size at a SID of 100 centimeters shall be equal to or less than 5 centimeters by 5 centimeters.

DHS 157.77(8)(b)4.4. The PBL system shall be designed such that a change in image receptor causes the automatic return to PBL.

DHS 157.77(8)(c)(c) Beam limitation for portable x-ray systems. Beam limitation for portable x-ray systems shall meet the beam limitation requirements for manual collimators.

DHS 157.77(9)(9) 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 hand-held during exposures.

DHS 157.77 HistoryHistory: CR 01-108: cr. Register July 2002 No. 559, eff. 8-1-02; CR 06-021: r. and recr. (5) Register October 2006 No. 610, eff. 11-1-06; CR 09-062: am. (2) (g) Register April 2010 No. 652, eff. 5-1-10; CR 16-078: am. (2) (h) 1., (i) Register January 2018 No. 745, eff. 2-1-18.

DHS 157.78(1)(1) General. In addition to the provisions of ss. DHS 157.74 and 157.75, the requirements in this section apply to x-ray equipment and associated facilities used for dental radiography. Requirements for extraoral dental radiographic systems are contained in s. DHS 157.77.

DHS 157.78(2)(2) 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 either one of the following: