A regional survey for mammographic systems

Performance tests of 26 analog mammographic units manufactured by nine different companies were carried out. Measurement protocols and recommended limits were taken from different organizations. Test of tube output (radiation output of the X ray tube, repeatability of output, variation of output with tube voltage, current and target/filter combination), check of kVp calibration, accuracy of beam alignment for different collimations, tests of automatic exposure control were made. ESAK values were measured for Perspex phantoms of different thickness in order to estimate the breast dose of any size. Tests for automatic film processors, dark rooms and film/screen combinations were carried out together with film sensitometry measurements. Qualitative and quantitative evaluations of image quality were performed using different phantoms. Tube outputs of six (6) systems were in the desirable range (40-49 μGy/mAs). Outputs of 18 systems were within the 31-39 μGy/mAs, and there were two systems with the outputs of 28 and 30 μGy/mAs. Repeatability of all systems were within the normal limits. The calibration of kVp was tested mainly at 28 kVp and, with the exception of one system, maximum deviations for all the others remained within the 5%. HVL tests were carried out at 28 kVp and all the systems were found within the recommended limits. 2, 4, 6 cm of Perspex slabs were used for the performance measurement of automatic exposure control (AEC). The results of nine (9) systems were in acceptable limits, AEC of four (4) systems was not functioning and the results of the remaining 13 systems were not within the suggested limits.The ESAK values were measured for 2,4 and 6 cm Perspex slabs, glandular doses were calculated for 4.5 cm breast thickness. The measured values were between 0.4 and 2.97 mGy with a mean of 1.46 mGy. X ray field/image receptor alignment tests were made both for 18x24 cm and 24x30 cm cassette sizes. X ray field/light field misalignment was found for 12 systems. There were eight systems that indicated alignment errors between the X ray field and exposed film area. The alignment of chest wall edge with the film area was not within the limits for three systems. There were wide variations of film-screen combinations. The screens of Kodak MinR 2000, Kodak MinR-2, Kodak Min R 2190, Agfa Mamoray HDS, Agfa Mamoray MR Detail, Konica MD100 were in use with the films from different manufacturers (Retina, Kodak Min R, Konica CM H, Agfa HDR, Primax RTG, Life Ray). Screen/film contact tests of 180 pairs were performed and 44 of them were found to be in poor condition. The films from 18 centres were exposed with a sensitometer, and H-D curves were analysed. The mean and variations of base plus fog level and average gradient were 0.21 (0.16-0.28) O.D and 2.72 (1.19-3.2) O.D., respectively. Variation of relative speed was 1.41 and 2.03. in the range of The measured range of developer temperatures of the automatic film processors were 28 deg.-37 deg.. The test of seventeen dark rooms were also performed using the films exposed with sensitometers and considerable light leaks were inspected for nine of them. CIRS Model 11 A and GE MTM 100 phantoms were used for the test of image qualities. In addition to the visual evaluation of images, spatial resolutions parallel and perpendicular to anode-cathode axis were also measured with the line pair test pattern insert of CIRS phantom. The resolving power of four systems were not within the tolerances. The measured mean ESAK value was 9.91 mGy and the results were within 3.9 mGy and 14.9 mGy. Image qualities of 21 systems were also measured with a GE MTM 100 phantom which has a scoring feature. The range of scores was between the 4 and 48, and the score of 3 systems were lower then threshold value given by the phantom manufacturer. The mean ESAK value of 9.02 mGy was found for this phantom