Section 157.77. General purpose radiographic systems.

 

(1)   Beam limitation.

(a) Collimation. The useful beam shall be limited to the area of clinical interest. This requirement is met if a positive beam-limiting device meeting manufacturer's specifications has been properly used or if evidence of collimation is shown on at least 3 sides or 3 corners of the film. Mammography systems are exempt from the collimation requirement.

(b) General purpose stationary and mobile x-ray systems. General purpose stationary and mobile x-ray systems, including veterinary systems other than portable, shall meet both of the following requirements:

1. Only x-ray systems provided with means for independent stepless adjustment of at least 2 dimensions of the x-ray field may be used.

2. 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 may 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) Stationary general purpose x-ray systems. Stationary general purpose x-ray systems, both certified and non-certified, shall meet all the following requirements:

1. 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 2% of the SID and to indicate the SID to within 2%.

2. The beam-limiting device shall indicate numerically the field size in the plane of the image receptor to which it is adjusted.

3. Field size dimensions and SIDs shall be specified in inches or centimeters and shall ensure that aperture adjustments result in x-ray field dimensions in the plane of the image receptor that 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.

(d) 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.

(e) Miscellaneous and veterinary x-ray systems. X-ray systems other than those described in pars. (a) to (c) , veterinary systems installed prior to the effective date of August 1, 2002, and all portable veterinary x-ray systems shall meet all of the following requirements:

1. 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.

2. 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.

3. The requirements in subds. 1. and 2. may be met with a collimator system that meets the requirements for a general purpose x-ray system or, when alignment means are also provided, may be met with either of the following:

a. 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.

b. A beam-limiting device with 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 that each aperture is designed for and shall indicate which aperture is in position for use.

(2)   Radiation exposure control.

(a) Exposure initiation. 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 may not be initiated without such an action. In addition, exposure may not be initiated when the timer is set to a "zero" or "off" position if either position is provided.

(b) 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.

(c) 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."

(d) Manual exposure control. An x-ray control shall be incorporated into each x-ray system so that the operator may terminate an exposure at any time except for any one of the following:

1. Exposure of 0.5 second or less.

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

(e) Automatic exposure controls. When an automatic exposure control is provided, it shall meet all the following requirements:

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 2 pulses.

3. The minimum exposure time for all equipment other than field emission equipment shall be equal to or less than one-sixtieth second or a time interval required to deliver 5 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.

5. A visible signal shall indicate when an exposure has been terminated and manual resetting shall be required before further automatically timed exposures may be made.

(f) Exposure duration linearity. For systems having independent selection of exposure time settings, the average ratios of exposure to the indicated timer setting, in units of .001mGy/s (mR/s), obtained at any 2 clinically used timer settings may not differ by more than 0.10 times their sum as expressed as:

(X 1 - X 2 ) < 0.1 (X 1 + X 2 )

where X 1 and X 2 are the average .001 mGy/s (mR/s).

(g) Exposure control location. The x-ray exposure control shall be placed so that the operator may view the patient while making any exposure and at least 1 meter (3.3 feet) from the end of the protective barrier.

(h) Operator protection, except veterinary systems. X-ray systems, excluding veterinary systems, shall meet all the following requirements to protect the operator during system use, as applicable:

1. 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.

2. Mobile and portable x-ray systems used continuously for greater than one week in the same location shall meet the requirements of stationary systems.

3. Mobile and portable x-ray systems used for less than one week at the same location shall be provided with either a protective barrier at least 2 meters (6.5 feet) high for operator protection during exposures or a means to allow the operator to be at least 2 meters (6.5 feet) from the tube housing assembly during the exposure.

(i) Operator protection for veterinary systems. All stationary, mobile or portable x-ray systems used for veterinary work shall be provided with either a 2 meter (6.5 feet) high protective barrier for operator protection during exposures or a means to allow the operator to be at least 2 meters (6.5 feet) from the tube housing assembly during exposures. Persons restraining the animal during radiography shall be protected with at least 0.5mm lead aprons and full coverage gloves or full coverage mittens containing not less than 0.5mm lead equivalent material. The exposure control may be foot operated.

(3)   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.

(4)   Air kerma reproducibility. When all technique factors are held constant, including control panel selections associated with automatic exposure control systems, the coefficient of variation of air kerma for both manual and automatic exposure control systems may not exceed 0.05. This requirement applies to clinically used techniques.

(5)   Radiation from capacitor energy storage equipment in standby status. Radiation emitted from the x-ray tube when the system is fully charged and the exposure switch or timer is not activated may not exceed any of the following:

(a) A rate of 0.26mGy (0.03mR exposure) in one minute at 5 centimeters from any accessible surface of the diagnostic source assembly with the beam-limiting device fully open.

(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.

(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.

(7)   m A/ m As 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:

(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:

X 1 -X 2 < 0.10 (X 1 +X 2 )

where X 1 and X 2 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.

(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:

X 1 -X 2 < 0.10 (X 1 +X 2 )

where X 1 and X 2 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.

(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.

(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:

(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:

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.

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.

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 I 1 /I 2 where I 1 is the illumination 3 millimeters from the edge of the light field toward the center of the field; and I 2 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.

(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:

1. PBL shall prevent the production of x-rays when either one of the following occurs:

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.

b. The sum of the length and width differences, without regard to positive or negative mathematical sign, exceeds 4% of the SID.

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.

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.

4. The PBL system shall be designed such that a change in image receptor causes the automatic return to PBL.

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

(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.

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.