Dosimetric and Contrast Noise Ratio Comparison of Three Different Digital Imaging Technologies in Mammography

The purpose of the study was to compare the three most common technologies available in digital mammography based in the evaluation of average glandular dose and contrast noise ratio (CNR).

The average glandular dose was estimated with a direct digital detector (aSe) with a pixel size of 0.85 μm, a photon counter with a pixel size of 50 μm and a computerized radiography (CR) system. A semiconductor detector was used to measure the input kerma to the detector, and the average glandular dose was calculated from the conversion factors dependent on the anode filter combination, half value layer and breast glandularity.

The average glandular dose obtained with polymethyl methacrylate and CNR of mean thickness 4.5 cm using direct digital equipment was 1.02 mGy and CNR = 7.4; using the photon counter it was 0.43 mGy and CNR = 4.7 in C100 mode, and 0.64 mGy and CNR = 5.7 in C120 mode; and using the photostimulable CR, the estimated value was 1.65 mGy and CNR = 5.1.

The photon counter offers a lower average glandular dose than the other two devices with adequate image quality (CNR). The CR equipment offers a similar CNR value but delivers a higher dose than the new generations of available mammograms.