Image Quality and Radiation Dose for Fibrofatty Breast using Target/filter Combinations in Two Digital Mammography Systems

Abstract

Objectives: The aim of this study was to determine the optimum combinations of target and filter materials for various X-ray tube voltage settings, as well as their effects on image quality and radiation dose. This was done using different digital mammography (DM) imaging systems with a breast equivalent phantom. Material and Methods: Two DM units with a tungsten (W) target, silver (Ag), and rhodium (Rh) filters and dual molybdenum (Mo) and Rh targets/filters were used. A tissue-equivalent mammography phantom of 6 cm thickness equivalent to a fibrofatty breast was exposed 20 times to different target/filter material combinations (W/Rh, W/Ag, Rh/Rh, Mo/Rh, and Mo/Mo) and various kV settings (28–34 kV). The signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were calculated for each exposure. Results: The W/Ag combination resulted in the lowest entrance skin dose and mean glandular dose (MGD). The MGD for the W/Rh combination was 60% less than that of the W/Ag combination at 34 kV (P < 0.05). There was a direct relationship in the SNR with the Mo/Mo, Mo/Rh, and Rh/Rh combinations and an inverse relationship with the CNR in the 34 kV range. There were statistically significant differences between all five target/filter combinations, and the best SNR and CNR were observed for the W/Rh combination with a reduced radiation dose in the range of 28–30 kV (P < 0.05). Conclusion: For a breast thicknesses of 6 cm with a fibrofatty nature, the W/Rh combination delivers high performance in terms of image quality at a lower dose.

An evaluation of the present status of quality assurance program implementation in digital mammography facilities in a developing country

“…The wide distribution and moderately right-skewed distribution in the box plots of HVL, D G , SNR, and CNR (figures 3-6) contrast with the narrowed distribution previously reported [16,25], and this could be attributable to the intermittent QAP/QC evaluation reported in this work, which increases the probability to cross the threshold of out-of-tolerance values [3,9,16,34,36]. However, the average HVL [25,37] and D G [8,16,17,37] results obtained agreed with those previously reported.…”

“…A QAP includes quality control (QC) tests and quality administration procedures, and should be updated throughout the entire operation of the establishment [6]. Even though the risk of cancer induction associated with mammography acquisition is relatively low, a QC protocol application (as a part of a QAP) is mandatory, in order to guarantee that subtle contrast differences among healthy breast tissues and breast abnormalities (masses or microcalcifications) are well differentiated in the diagnostic image [7][8][9].…”

“…On the other hand, prior to patient image acquisition, commissioning QC tests must be performed within the mammography unit by qualified personnel (such as the MP) and, subsequently, frequent QCs must be carried out to ensure that the equipment works properly. The presence of a phantom (even a simple one, such as polymethylmethacrylate slabs) is a basic tool to follow up the presence of artifacts, consistency of exposure factors, exposure index behavior, compression scale accuracy, or any other short-term fluctuations in the components of the image chain [6,9,10]. The absence or incorrect implementation of a QC phantom puts the patient's safety and mammography at risk.…”