Development and evaluation of rotating multi-segment variable-angle slant-hole SPECT

Abstract

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Objectives: Previously we developed a SPECT technique using rotating multi-segment slant-hole (RMSSH) collimator that provides much higher (~3×) detection efficiency than the parallel-hole collimator with the same spatial resolution at the cost of limited common-volume-of-view (CVOV). The goal of this study is to develop and evaluate the performance of a new rotating multi-segment variable-angle slant-hole (RMSVASH) collimator for SPECT that gives a larger CVOV with minimum decrease in detection efficiency. Methods: Unlike RMSSH collimator where each segment consists of parallel holes slanted at a fixed angle, the collimator holes in each segment of a RMSVASH collimator are slanted at variable angle to form planar diverging-beam geometry. Analytical formulas were derived to theoretically calculate geometry parameters and performance characteristics. Iterative OS-EM reconstruction algorithm for RMSVASH SPECT was developed by incorporating the slanted planar diverging-beam geometry in the rotating-shearing projector-backprojector pair, which modeled the photon attenuation and collimator-detector response (CDR) effects in attenuation (AC) and CDR compensations, respectively. To evaluate the performance of RMSVASH SPECT, we used myocardial perfusion and breast SPECT projection data generated from the 3D NCAT phantom using analytical projectors. Projections were reconstructed using OS-EM algorithm with compensations. Results: Compared to RMSSH collimator with the same collimator thickness and hole-size, RMSVASH collimator provides a CVOV that is 110% larger in volume for a decrease of 40% in detection efficiency at the center of the CVOV. The reduced detection efficiency is still 1.7 times higher than parallel-hole collimator with the similar resolution. For both without and with CDR compensation, RMSVASH SPECT images showed an increased CVOV with reduced image artifact. The increased CVOV is particularly important in breast SPECT to image the lesions in the entire chest wall. Conclusions: We developed a new SPECT imaging technique with RMSVASH collimator that has a significantly larger CVOV with a minimum decrease in detection efficiency as compared to RMSSH collimator. The increased CVOV of RMSVASH collimator allows SPECT imaging of the breast that includes the entire chest wall and of large hearts with easier patient positioning.

Research Support (if any): R01-EB1983