Investigation of Exposure Factors for Various Breast Composition and Thicknesses in Digital Screening Mammography Related to Breast Dose

Abstract

Objective: To investigate the effect of exposure factors used in digital screening mammography on image quality of different breast compositions. Material and Methods: A digital mammography unit, with tungsten (W) as target, rhodium (Rh) and silver (Ag) as filters, and amorphous selenium detectors, was used to image Computerized Imaging Reference Systems (CIRS) Model 12A phantoms of thickness 4, 5, and 6 cm. Images of each phantom were obtained using target-filter combinations of W/Rh and W/Ag, at 28, 30, and 32 kVp. Images were evaluated by 5 senior technologists with experience in mammography. Image scores were assigned, for each type of feature present in the phantom. Statistical analysis was performed using nonparametric tests to compare sets of image scores at p = 0.05. Results: A small but statistically significant improvement was detected in the visibility of microcalcifications (8.8 ± 0.2; p = 0.031) for the W/Rh combination but this did not show any differences in the visibility of masses or fibers. The entrance skin dose (ESD) and mean glandular dose (MGD) were lower for the W/Ag (ESD = 1.30–3.70; MGD = 0.44–0.93 mGy) combination compared to W/Rh (ESD = 1.66–5.40; MGD = 0.52–1.12 mGy). The Mann-Whitney test revealed that 30-kV exposure with the W/Rh combination showed a significantly better visibility of specks in the 30/70 phantom compared to other exposures. Conclusion: The use of an Rh filter showed a better image quality for all phantoms. 28 and 30 kVp with the W/Rh combination provided a slightly better image quality, and the MGD is less than 1.2 mGy.

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

“…The previous studies have shown that the W/Rh combination is always the optimum choice to deliver high performance in terms of image quality at a lower dose, [ 20 , 21 ] but they did not specify the breast thickness. The CNR for a 34 kV Rh filter was significantly better than that for other kV values ( P = 0.027).…”

“…[ 19 ] There are reports of using the W/Rh combination for compressed breast thicknesses ranging from 4 to 6 cm and different breast glandularities, which delivered high performance in terms of image quality at a lower radiation dose. [ 20 , 21 ] The main aim of this study was to determine the effects on the image quality and radiation dose of different combinations of target/filter materials with various settings of the X-ray tube voltage. Two DM imaging systems were used on a 6 cm thickness equivalent breast phantom containing materials equivalent to 20% glandular tissue and 80% adipose tissue.…”

Comparison of Digital Breast Tomosynthesis and Digital Mammography for Detection of Breast Cancer in Kuwaiti Women

“…Radiation dose is cumulative over time, so it is prudent to limit exposure to DBT. A further dose reduction can be achieved by using a target/filter combination of tungsten/rhodium as suggested recently [28]. As we mentioned previously, DBT has already been implemented in Kuwait for the last 5 years.…”

Kuwait National Mammography Screening Program: outcomes of 5 years of screening in Kuwaiti women

“…The most notable of these drawbacks is that some of the malignancies may be missed or misinterpreted; there is a restricted opportunity to image microcalcification and there is a concern with the radiation dose. 23 – 26 In addition, in Kuwait, digital breast tomosynthesis (DBT) is not used as a screening tool. Despite DBT having a few drawbacks, several authors are investigating the possibilities of using it effectively in screening.…”