Phantom Evaluation of a Multi-Pinhole Cardiac SPECT Camera for 3D Molecular Breast Imaging

A tomographic clinical cardiac SPECT system consisting of many static CZT-based pinhole gamma cameras is evaluated for dedicated, pendant 3D molecular breast imaging. The reconstructed spatial resolution and linearity of the spherically symmetric FOV were evaluated with a multi-point source array. A series of anthropomorphic phantom imaging measurements using 0.4 and 0.9 mm diameter lesions was performed; lesion-to-background ratios ranged from[13:1] to [3:1] to simulate various biological uptake; three breasts used were 470-1730 mL in volume. Basic contrast, CNR and coefficient of variation were measured with the anthropomorphic torso+organ background. Decreasing acquisition times from 30030 sec were a surrogate for lower injected doses. All data was reconstructed using MLEM with various iterations on the commercial workstation. Results indicate that the system largely behaves in the expected way: better overall resolution, linearity, sensitivity, and uniformity closer to the detectors but within the FOV. Other key observations include: (1) higher lesion: background ratios yielded higher image contrast and CNR; (2) lesion contrast and CNR appeared independent of acquisition time; (3) breast size had less of an effect on lesion metrics, but yielded decreased out-of-field (e.g., cardiac and hepatic) contributions with larger breasts. These results indicate that lower injected doses could be utilized for 3D MBI. While additional optimization would be beneficial for breast imaging, this high sensitivity SPECT system could be used for dynamic 3D MBI for lesion diagnostics or therapeutic monitoring.