1997 Volume 6 Issue 2 Pages 175-183
The success of screening mammography depends on the production of high-quality and low -dose images. Achieving high-quality studies at low dose requires vigilant attention to quality control for everyone involved in breast cancer screening. We evaluated 14 mammography units in Gunma Prefecture as outlined in the American College of Radiology Mammography Quality Control Manual (Revised Edition, 1994).
We selected five quality control programs from the ACR-QC-Manual.
1) Automatic exposure control (AEC) system performance assessment
2) RMI-156 phantom images
3) High-contrast resolution pattern measurement of limiting resolution
4) Beam quality assessment half value layer measurement
5) Breast entrance exposure average glandular dose
[Results]
1) In evaluation of the AEC system, the maximum difference in film density at each thickness of the acrylic slab (2, 4, 6 cm) was 0.71. Upon comparison of film density with the same thickness of acrylic slab in each unit, the maximum difference in film density was more than 1.0.
2) The RMI-156 phantom image of each unit passed 64.3% of the ACR mammography accrediation.
3) In measuring limiting resolution, the smaller focus size of the X-ray tube gave higher resolution. However, there was considerable difference even with the same type of unit.
4) All units with a Mo filter for HVL passed the ACR mammography accreditation.
5) The average glandular dose was regulated to lower than 3 mGy with the grid, but one of the units without such a grid had a value of over 1 mGy. The mean dose was 1.23 mGy with the grid, and 0.94 mGy without.
