Evaluation of different target/filter combinations in mammography equipment in terms of image quality and mean glandular dose

Contrast-to-Noise Ratio (CNR) is one of the most frequently adopted metric for evaluating digital radiographic image quality, being positively correlated with image quality. However, the increase in CNR is conditioned to an increment in Mean Glandular Dose (MGD) in patients. The objective of the study was to verify if the target/filter combination interferes in the relationship between CNR and MGD and, thus, to analyze the best combination to balance image quality and dose in the patient. In total, 98 images of the breast simulator Phantom Mama, for a breast simulating phantom 50mm thick, were acquired for the target/filter combinations Mo/Mo and W/Rh. For all images, we employed a voltage of 28kV and variable current-time product (mAs) in a Siemens Mammomat Inspiration digital mammography equipment. A linear relationship was observed between AGD and mAs with coefficients of determination (R²) equal to 0.99994 (Mo/Mo) and 0.99999 (W/Rh), and a linear relationship between MGD and CNR² with coefficients of determination (R² ) equal to 0.912 (Mo/Mo) and 0.944 (W/Rh). The angular coefficients indicate that the W/Rh combination has a higher CNR² for the same MGD value compared to Mo/Mo. It was concluded that W/Rh combination provides a higher image quality for the same irradiation conditions as the phantom conditions. (author)