(Wednesday, 7/17/2019) 9:30 AM - 10:00 AM
Room: Exhibit Hall | Forum 9
Purpose: To quantify the impact of uniform, and sparse-view non-uniform angular sampling in short-scan (270-degree) acquisition, compared to the conventional 360-degree acquisition on microcalcifications in dedicated cone-beam breast computed tomography (CT).
Methods: Nine cases with calcified lesions were selected from an existing database of full-scan (360-degrees; 300 views) clinical dedicated breast CT exams. Traditional Feldkamp-Davis-Kress (FDK) reconstruction of the full-scan data served as the reference. Projection data encompassing 270-degree short-scan acquisitions were selected with uniform angular sampling (225 views) and sparse-view, non-uniform angular sampling (180 and 168 views) were selected. FDK with Parker weights (FDK-PW) and adaptive steepest descent-projection onto convex sets (ASD-POCS) were used for short-scan reconstruction. Image quality was quantified by signal-difference to noise ratio (SDNR) between adipose and fibroglandular tissue, full-width at half-maximum (FWHM) of calcifications in two orthogonal directions, and bias and root-mean-squared-error (RMSE) computed with respect to reference. Median (interquartile range) was used for comparison.
Results: SDNR (median) of short-scan ASD-POCS (62.7) outperformed the reference (44.1) and the short-scan FDK-PW (35.6). For short-scan, FDK-PW compared to ASD-POCS showed shading artifacts, increased bias (median: -41.9x10^-3 vs. -6.1x10^-3, in units of 1/cm) and increased RMSE (median: 7.8x10^-2 vs. 1.8x10^-2, in units of 1/cm). The FWHM of FDK-PW and ASD-POCS were similar to reference (median difference of 0%), indicating comparable spatial resolution. Non-uniform, sparse-view reconstructions did not show an appreciable trend in RMSE, bias and FWHM, with a small trend of decrease in SDNR with reduction in number of views that is theoretically consistent.
Conclusion: This study indicates the feasibility of uniform and non-uniform angular sampling in short-scan and sparse-view acquisition using compressed sensing-based iterative reconstruction. This indicates that shorter scan times and reduced radiation dose without sacrificing image quality is potentially feasible. Fine-tuning of parameters with additional clinical cases is planned for a future reader study.
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