Only x-ray systems meeting the design and performance standards required under Mammography Quality Standards Act (MQSA) shall be used, unless otherwise specified in the following rules.
System design. The x-ray system shall be specifically designed for mammography.
Image receptor systems shall be specifically designed, or appropriate for mammography.
Systems using screen-film image receptors shall provide, at a minimum, image receptor sizes of 18 X 24 and 24 X 30 cm.
An adequate number of image receptors shall be provided to accommodate the resting period recommended by the manufacturer.
Target/filter. The x-ray system shall have the capability of providing kVp/target/filter combinations compatible with image receptor systems meeting the following requirements;
When more than one focal spot is provided, the system shall indicate, prior to exposure, which focal spot is selected.
When more than one target is provided, the system shall indicate, prior to exposure, the preselected target material.
When the target material and/or focal spot is selected by a system algorithm that is based on the exposure or on a test exposure, the system shall display, after exposure, the target material and/or focal spot actually used during the exposure.
Beam quality: When used with screen-film image receptors, and the contribution to filtration made by the compression device is included, the useful beam shall have a minimum half-value layer (HVL). The minimum HVL, for mammography equipment designed to operate below 50 kVp, is determined by dividing the actual kVp by 100, and is expressed in mm Al equivalent.
Resolution: Until October 28, 2002, focal spot condition shall be evaluated either by determining system resolution or by measuring focal spot dimensions. After October 28, 2002, facilities shall evaluate focal spot condition only by determining system resolution.
Each x-ray system used for mammography, in combination with the mammography screen-film combination used, shall provide a minimum resolution of 11 Cycles/mm (line-pairs/mm) when a high contrast resolution bar test pattern is oriented with the bars perpendicular to the anode-cathode axis, and a minimum resolution of 13 line-pairs/mm when the bars are parallel to that axis.
The bar pattern shall be placed 4.5 cm above the image receptor support surface, centered with respect to the chest wall edge of the image receptor, and with the edge of the pattern within 1 cm of the chest wall edge of the image receptor.
All mammography systems shall incorporate a compression device capable of compressing the breast with a force of at least 25 pounds.
Effective October 28, 2002, the maximum compression force for the initial power drive shall be between 25 pounds and 45 pounds.
All mammography systems shall be equipped with different sized compression paddles that match the sizes of all full field image receptors provided for the system. The compression paddle shall:
Be flat and parallel to the image receptor support and shall not deflect from parallel by more than 1.0 cm at any point on the surface of the compression paddle when compression is applied. If the compression paddle is not designed to be flat and parallel to the image receptor support during compression, it shall meet the manufacturer’s design specifications and maintenance requirements;
Have a chest wall edge that is straight and parallel to the edge of the image receptor support;
Clearly indicate the size and available positions of the detector at the x-ray input surface of the compression paddle;
Not extend beyond the chest wall edge of the image receptor support by more than 1 percent of the SID when tested with the compression paddle placed above the support surface at a distance equivalent to a standard breast thickness;
Shall not be visible, at its vertical edge, on the image.
When equipped with a compression paddle height digital display, the display shall accurately represent the actual height of the compression paddle to within +- 0.5 cms. Testing shall be performed according to manufacturer’s specifications.
System capabilities. A mammographic x-ray system utilizing screen-film image receptors shall:
Be equipped with moving grids matched to all image receptor sizes provided.
Provide an AEC mode that is operable in all combinations of equipment configuration provided, e.g., grid, non-grid, magnification; and various target-filter combinations.
The automatic exposure control shall be capable of maintaining film optical density (OD) within +0.30 of the mean optical density when thicknesses of a homogeneous material are varied over a range of 2 to 6 cms and the kVp is varied appropriately for such thicknesses over the kVp range used clinically. If this requirement cannot be met, a technique chart shall be developed showing appropriate techniques (kVp and density control settings) for different thicknesses and compositions that must be used so that optical densities within + 0.30 of the average under photo- timed conditions can be produced.
After October 28, 2002, the AEC shall be capable of maintaining film optical density (OD) to within + 0.15 of the mean optical density when thicknesses of a homogeneous material are varied over a range of 2 to 6 cm and the kVp is varied appropriately for such thicknesses over the kVp range used clinically.
Breast entrance kerma and AEC reproducibility. The coefficient of variation for both air kerma and mAs shall not exceed 0.05.
All mammography systems shall have beam-limiting devices that allow the entire chest wall edge of the x-ray field to extend to the chest wall edge of the image receptor and provide means to assure that the X-ray field does not extend beyond any edge of the image receptor by more than 2 percent of the SID. Under no circumstances, shall the x-ray field extend beyond the non-chest wall edges of the image receptor support.
The total misalignment of the edges of the visually defined light field with the respective edges of the X-ray field either along the length or width of the visually defined field shall not exceed 2 percent of the SID.
Kilovoltage peak (kVp) accuracy and reproducibility;
The kVp, shall be accurate within + 5 percent of the indicated or selected kVp at the lowest clinical kVp that can be measured by a kVp test device, and the most commonly used, and highest available clinical kVp; and
At the most commonly used clinical settings of kVp, the coefficient of variation of reproducibility of the kVp shall be equal to or less than 0.02.
Dose. The average glandular dose delivered during a single cranio-caudal view of an FDA accepted phantom simulating a standard breast, shall not exceed 250 millirad (mRad) (2.5 milliGy). The dose shall be determined with technique factors and conditions used, by the registrant, clinically for a standard breast. The testing protocol used shall be the same as used by MQSA.
If the average glandular dose exceeds 250 mRad (2.5 milliGray) but is no greater than 275 mRad (2.75 milliGray), patient mammography may be continued until the cause of the problem is determined and corrected. Correction must be completed within 30 working days of when the registrant became aware of the problem. If correction has not been completed within 30 working days, and the registrant has not requested an extension in writing from the Authority, patient mammography must cease until correction of the dose problem has occurred.
If the average glandular dose exceeds 275 mRad (2.5 milliGray), patient mammography must cease until the cause of the dose problem is determined and corrected.