Projection imaging such as digital mammography (DM) suffers from superimpositions, especially in dense breasts. Breast tomosynthesis (BT) and dedicated breast computed tomography (BCT) try to overcome this disadvantage. The study compared the performance of DM, BT, and BCT in detecting high- and low-contrast objects with and without superimposing structures as a function of average glandular dose (AGD).
METHOD AND MATERIALSThe performance of DM and BT using standard clinical systems and protocols was compared to a novel photon-counting BCT (pcBCT). Two breast-equivalent phantoms mimicking a compressed breast (for DM/BT) and a pendant breast (for pcBCT) were used. Both phantoms offer cubical (4 cm)³ cavities to be filled with up to 64 cubical (1 cm)³ breast equivalent inserts. Structures of varying size (130–530 µm calcifications (µCa), 1–8 mm lesions) and shape (spheres and fibrils) were embedded in 16 inserts. These 16 test structures were arranged randomly in one or two transverse planes of interest (POI). The positions of the POIs were varied in different distances to the phantom border and to each other. Superimpositions were simulated by placing organic structures above and below the POIs. Images were acquired with and without superimpositions using AGD levels from 1 to 10 mGy. Receiver operating characteristics were determined for five observers with respect to the detectability of the test structures.
RESULTSThe detection rates for test structures without superimpositions were similar in DM, BT and pcBCT for AGD below 5mGy: detection of 2 mm lesions in BT and pcBCT, 4 mm in DM; detection of 160 µm µCa pcBCT, 250 µm in DM and BT. When superimposing structures were present the detection rates remained constant in pcBCT. They were superior compared to DM and BT especially regarding low contrast objects: detection of 2 mm lesions in pcBCT, no lesion detection in DM and BT; detection of 160 µm µCa in pcBCT, 250 µm in BT, and 530 µm in DM.
CONCLUSIONBT showed higher performance than DM. pcBCT outperformed DM and BT due to superior detectability performance for calcifications and low-contrast objects owing to higher image contrast and the absence of superimpositions.
CLINICAL RELEVANCE/APPLICATIONpcBCT offers the opportunity to increase sensitivity and specificity in early detection of breast cancer and thus the potential to improve the diagnostic accuracy compared to DM and BT.