Illinois Administrative Code › Title 32 - ENERGY › Part 370 - QUALITY STANDARDS AND CERTIFICATION REQUIREMENTS FOR FACILITIES PERFORMING MAMMOGRAPHY › Appendix A - Mammography Dose Measurement Protocol

Current through Register Vol. 48, No. 28, July 12, 2024
The technique factors used for performing a mammography
				examination shall not permit the mean glandular absorbed dose to exceed the
				limits specified in Section
				370.110(e)(7)
				of this Part. Radiation measurements shall be performed with an integrating
				radiation measuring device that is appropriate to the high beam intensity and
				mammographic kilovoltage peak (kVp) used, and sufficiently sensitive to
				determine compliance with the criteria specified in Section
				370.110(i)(2)
				of this Part. The instrument shall have been calibrated as specified in Section
				370.110(i)(2)
				of this Part.
The mammography exam dose limits are based on an average
				compressed breast value of 4.2 centimeters having an average density (i.e., 50
				percent adipose and 50 percent glandular).
Perform the following steps to determine the mean glandular
				dose to a nominal 4.2 centimeter compressed breast:
a) Measure and record the x-ray system's useful beam
				half-value layer (HVL). (See Section 370.110(e)(5) of this Part.) Any
				compression device normally in the useful beam during mammography procedures
				shall be required to be placed between the x-ray tube target and measuring
				device when determining the HVL. The useful beam shall be collimated to a size
				encompassing the detector.
AGENCY NOTE: Filters used for the HVL evaluation
				should be placed as close to the target as practical. The HVL for screen-film
				mammography should not exceed the minimum acceptable HVL by more than 0.1
				millimeter of aluminum equivalent.
b) Determine the glandular dose to entrance exposure
				factor from the Mammography Dose Evaluation Table (see Table A of this Part)
				using the appropriate HVL, kVp and x-ray tube target-filter material.
AGENCY NOTE: The kVp of screen-film mammography
				systems with molybdenum target-filter combinations should be accurately
				measured to determine the appropriate glandular dose to entrance exposure
				factor from Table A of this Part.
c) If the equipment has the capability for variable
				source-image receptor distance, set the craniocaudal source-image receptor
				distance (SID) for the image receptor system used.
d) Position in the useful beam any compression
				apparatus normally used.
AGENCY NOTE: Some mammography systems have the
				capability of providing automatic adjustment of technique factors through
				feedback from the position of the compression device. On such systems, the
				compression device should be lowered to a position 4.2 centimeters above the
				breast support assembly (BSA). The device should then be removed, inverted and
				replaced to allow placement of the phantom and measuring device on the BSA
				below the compression device. If the compression device cannot be replaced in
				an inverted position, the device should be placed in the beam using auxiliary
				support.
e) Placement of the Radiation Measuring
				Device
1) For systems equipped with automatic exposure
				control (AEC):
A) Place a properly loaded film cassette in the
				cassette holder.
AGENCY NOTE: The loaded cassette is placed in the
				cassette holder to simulate, as much as is possible, the conditions under which
				actual patient exposures are made. Following radiation measurements, the film
				should be discarded and the cassette reloaded with unexposed film.
B) Place a mammography phantom (see the definition
				for "Phantom" in Section 370.20 of this Part) on the breast support assembly
				(BSA). Align the phantom so that the edge of the phantom is aligned with the
				chest wall side of the BSA and the phantom is over the automatic exposure
				control device(s).
C) Place a radiation measuring device in the useful
				beam so the center axis of the device is parallel to the breast support
				assembly (BSA). The geometric center of the measuring device shall be
				positioned 4.5 centimeters above the BSA, 2.5 centimeters from the chest wall
				edge of the BSA and immediately adjacent to either side of the mammography
				phantom.
2) For systems not equipped with AEC, place a
				radiation measuring device in the useful beam so that the center axis of the
				device is parallel to the breast support assembly (BSA). The geometric center
				of the measuring device shall be positioned so that it is centered 4.5
				centimeters above the BSA, 2.5 centimeters from the chest wall edge of the BSA
				and at the center line of the BSA. No part of the device's detector area shall
				be outside of the useful beam.
f) Collimate the x-ray field to the size normally
				used and assure that the area covered by the useful beam includes the detector
				area of the radiation measuring device and the mammography phantom if the
				equipment is equipped with automatic exposure.
g) Set the appropriate technique factors or
				automatic exposure controls normally used for a nominal 4.2 centimeter
				compressed breast.
h) Measure and record the exposure in air with the
				radiation measuring device.
i) Calculate the mean glandular dose for a 4.2
				centimeter compressed breast by multiplying the measured exposure in
				millicoulombs per kilogram or in roentgens by the glandular dose to entrance
				exposure factor, which was determined using the procedure described in
				subsection (b) of this Section.
EXAMPLE: A mammography system is provided with a
				molybdenum target-filter combination, and the HVL and kVp are determined to be
				0.3 and 30, respectively. Therefore, for a 4.2 centimeter compressed breast,
				the glandular dose to entrance exposure factor from the Mammography Dose
				Evaluation Table (Table A of this Part) would be 159 mrad. The measured
				roentgen output determined in subsection (h) of this Appendix is determined to
				be 1.8 R. Therefore, the mean glandular dose would be 1.8 R multiplied by 159
				mrad/R. This results in a mean glandular dose measurement of 286 mrad. As such,
				the system would be in compliance with Section 370.110(e)(7) of this
				Part.