Study of the performance change in digital mammography systems depending on the total number of examinations

Abstract

Digital mammography equipment should operate at a high-performance level for detecting breast cancer over the lifetime of the systems. This study investigates the performance of the Fujifilm Amulet Innovality full-field digital mammography system in relation to the number of exposures. The performance of twelve systems, from new and up to 17 000 examinations, was compared. The x-ray output, half-value layer (HVL), contrast-detail (C-D) detectability, contrast-to-noise ratio (CNR), mean glandular dose (MGD), signal transfer property (STP), pre-sampled modulation transfer function (MTF), normalized noise power spectra (NNPS), detective quantum efficiency (DQE) tests were performed to determine the performance change. The noise sources were also analyzed in the spatial domain. The x-ray output and HVL values at 28 kV with tungsten anode and rhodium filter were 15 mu Gy/mAs +/- 1.0 (coefficient of variation (cov) = 7.0%) and 0.54 mmAl +/- 0.008 (cov = 1.5%), respectively. The average MGDs for 60 mm equivalent breast to reach the achievable image quality level for 0.1 mm and 0.25 mm detail diameters of circular discs on the CDMAM 3.4 phantom image were 1.17 mGy +/- 0.13 (cov = 11%) and 1.40 mGy +/- 0.09 (cov = 6%), respectively. The average MGD for 53 mm equivalent breast was 1.08 mGy +/- 0.14 (cov = 13%) at dose setting Normal in automatic exposure control (AEC) mode. All tested devices demonstrated good linearity with R-2 >= 0.999 in the STP curves. The average MTF at 5.0 mm(-1) spatial frequency was 0.66 +/- 0.007 (cov = 1.0%). The average NNPS was 2.38 x 10(-6) mm(2) +/- 2.13 x 10(-7) (cov = 9.0%) at 5.0 mm(-1). The average DQE value at 5.0 mm(-1) was 0.33 +/- 0.02 (cov = 5.0%), and the mean peak DQE was 0.66 +/- 0.03 (cov = 5.0%). The mean power coefficient (b), determined from the power relationship between linearised standard deviation and detector dose while analyzing noise sources, was 0.49 +/- 0.007 (cov = 1.4%). There was no gradual change in the x-ray tube and detector performance by the number of exposures, and taking up to 68 000 images did not decrease the quality of the systems.