Optimal Acquisition Parameters for Compressed Sensing-Based Sparse View, Upright, Cone-Beam Breast CT: Phantom Study
Abstract
Purpose
Cone-beam breast CT (CBBCT) offers volumetric imaging without tissue overlap, but achieving adequate image quality at screening-appropriate dose levels remains challenging. This study optimizes acquisition parameters for sparse-view acquisition and compressed sensing-based image reconstruction to achieve a targeted mean glandular dose (MGD) of 4.5 mGy while maintaining microcalcification visibility for a short-scan, upright, dedicated cone-beam breast CT (CBBCT).
Methods
A homogeneous breast phantom (20% glandular/80% adipose) containing test objects with microcalcifications (0.24 mm to 0.32 mm diameter CaCO3 spheres) was imaged using an upright CBBCT system at 60 kVp with 0.15 mm Cu filtration over a 210-degree short scan. Acquisition parameters were systematically varied, including X-ray tube current (40-50 mA), pulse width (18-20 ms), and angular sampling (sparse views). Reference acquisitions used 210 views (1 degree per view), yielding mean glandular doses (MGD) of 8.4-10.5 mGy. Images were reconstructed using the Fast, total variation-Regularized, Iterative, Statistical reconstruction Technique (FRIST), a compressed sensing algorithm. Image quality was assessed based on microcalcification visualization.
Results
FRIST reconstruction achieved visualization of 0.24 mm calcifications at the target MGD of approximately 4.5 mGy with sparse view acquisition. Three parameter combinations were evaluated to reach this dose level: 90 views at 50 mA/20 ms (baseline: 10.5 mGy), 100 views at 50 mA/18 ms (baseline: 9.47 mGy), and 114 views at 40 mA/20 ms (baseline: 8.4 mGy). Among these FDA-compliant protocols, 50 mA/20 ms with 90 views provided superior visualization of 0.24 mm calcifications. This optimized configuration achieved approximately 57% dose reduction from the reference while maintaining microcalcification visibility.
Conclusion
Optimization of acquisition parameters combined with FRIST compressed sensing reconstruction enables upright CBBCT to achieve MGD of 4.5 mGy and 0.24 mm microcalcification cluster visibility. Multiple viable parameter combinations provide flexibility for clinical implementation, supporting the translation of upright CBBCT for breast imaging.