Determining the Optimal Angular Range of the X-Ray Source Motion in Tomosynthesis Using Virtual Clinical Trials.

The limited angle and limited number of projections in digital breast tomosynthesis (DBT) produce under-sampled datasets that may compromise calcification detection. Small breast lesions, such as microcalcifications, may not be discernible without sufficient sampling in the reconstructed DBT images. We propose a virtual clinical trial (VCT) method to evaluate the calcification detection in DBT using computer simulations of breast phantoms, images, and virtual readers. We used multiple-reader multiple-case (MRMC) receiver operating characteristic (ROC) analyses to evaluate the performance of channelized Hotelling observers (CHOs) in calcification detection. The angular motion path of the x-ray source was varied to simulate different DBT acquisition geometries. We simulated continuous and step-and-shoot x-ray source motion and three angular motion paths: ±7.5°, ±15°, and ±25°. The detection of calcifications is affected by the angular motion path, particularly for the ±25° angular range, combined with continuous tube motion, larger detector element sizes (0.14 mm) and larger reconstructed voxel sizes (0.10 mm). When an angular range of ±25° is compared to ±7.5°, the difference in the area under the curve (AUC) is -0.030 (' ratio=0.633) and -0.067 (' ratio=0.584), for one- and two-voxel calcifications (0.1 mm and 0.2 mm), respectively. There is no significant difference in calcification detection using images acquired with ±7.5° and ±15°. The results provide insight on the impact of angular range for calcification detection, an ongoing limitation of tomosynthesis.