Investigation of cone-beam acquisitions implemented using a novel dedicated mammotomography system with unique arbitrary orbit capability
We investigate cone-beam acquisitions implemented on a novel dedicated cone-beam transmission computed mammotomography (CmT) system with unique arbitrary orbit capability for pendant, uncompressed breasts. We use a previously reported optimized quasi-monochromatic beam technique together with orbits made possible with a novel CmT gantry system, to evaluate Vertical-Axis-Of-Rotation (VAOR), Circle-Plus-Two-Arcs (CP2A), and Saddle trajectories. Acquisition parameters include: W target, 60 kVp tube potential, 100th VL Nd filtration, 1.25 mAs, 55 cm SID, Csl(Tl) digital flat panel x-ray detector, and 7.7cm diameter uniform disc (Défrise) and resolution phantoms. Complex orbits were also performed for a realistic breast phantom. Reconstructions used an iterative ordered subsets transmission (OSTR) algorithm with 4×4 binned projections, 8 subsets, and 10 iterations, with 0.125 mm 3 voxels. We evaluate the results for image artifacts, distortion, and resolution. Reconstructed images of the disc coronal and sagittal slices show significant distortion of the discs and phantom interfaces away from the central plane of the conebeam for VAOR, less distortion for CP2A, and minimal distortion for the complex 3D Saddle orbit. Resolution phantoms indicate no loss of resolution with the Saddle orbit, with the smallest 1.1mm diameter rods clearly resolved. Other image artifacts such as streaking were also significantly reduced in the Saddle orbit case. Results indicate that arbitrary orbits of pendant uncompressed breasts using cone-beam acquisitions and OSTR iterative reconstructions can be successfully implemented for dedicated CmT to improve angular sampling with significant reduction in distortion and other image artifacts. This capability has the potential to improve the performance of dedicated CmT by adequately sampling the breast and anterior chest volumes of prone patients with pendant, uncompressed breasts.
McKinley, RL; Brzymialkiewicz, CN; Madhav, P; Tornai, MP
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