Continuous Repetitive Data Acquisition with ¹²³I-FP-CIT SPECT: Effects of Rotation Speed and Rotation Time

The aim of this study was to evaluate the effects of the acquisition rotation speed and the rotation time for continuous repetitive rotation acquisition (CRRA) on image quality and quantification in ¹²³I-FP-CIT SPECT. Methods: An anthropomorphic striatal phantom filled with ¹²³I solution was acquired with CRRA and the step-and-shoot (SS) mode. The following combinations of acquisition rotation speed and rotation time for CRRA were used: 0.50 rpm by 30 frames, 0.17 rpm by 10 frames, 0.10 rpm by 6 frames, and 0.05 rpm by 3 frames. SPECT images were reconstructed using ordered-subset expectation maximization with resolution recovery, scatter, and CT-based attenuation correction. Two kinds of image processing patterns-image reconstruction after the addition of projection data (the added-projection-data process) and image addition after data reconstruction (the added-reconstructed-image process)-were investigated in this study. The effects of the acquisition parameters and the image processes were evaluated by the full width at half maximum, percentage coefficient of variation (%CV), and specific binding ratio (SBR). Results: With full width at half maximum, there were no clear differences between CRRA images obtained with the various rotation speeds before rotation and the SS mode. Although the combination of a slow rotation speed and a short rotation time improved image uniformity compared with the SS mode, the %CV obtained by CRRA increased as the rotation speed increased. The %CVs were 11.9% ± 0.9% for 0.50 rpm by 30 frames, 6.9% ± 0.9% for 0.05 rpm by 3 frames, and 9.6% ± 0.5% for SS mode. SBRs obtained by CRRA with the added-projection-data process were equal to those obtained by SS mode. However, SBRs obtained with the added-reconstructed-image process were clearly decreased compared with the SS mode. Conclusion: The combination of rotation speed and rotation times affects the image quality and quantification of ¹²³I-FP-CIT SPECT using CRRA. When CRRA is applied in ¹²³I-FP-CIT SPECT, it is necessary to use added-projection-data processes and proper rotation speeds (e.g., 0.10-0.17 rpm rotation speed).