Optimal ROI setting on the anatomically normalized I-123 FP-CIT images using high-resolution SPECT

OBJECTIVE: The aim of this study is to establish the optimal regions of interest (ROIs) in anatomically normalized I-123 FP-CIT SPECT images for the quantification of dopamine transporter binding. METHODS: The subjects comprised 16 normal controls and 14 Parkinsonian patients. All of the normal control subjects underwent I-123 FP-CIT SPECT and MRI. The SPECT device used in this study was a Toshiba GCA-9300R with triple head detectors. I-123 FP-CIT (148 MBq) was intravenously administered as a bolus, and the SPECT scan started 4 h after the administration. The data were collected over 20 min for each subject, and reconstructed using a 3D-OSEM algorithm. The data were analyzed using SPM8. I-123 FP-CIT SPECT images were anatomically normalized to the MNI space using an I-123 FP-CIT template, and then divided by the background counts automatically measured using the ROIs set for the cerebral cortices. RESULTS: In the normal control subjects, the specific binding ratios of the MRI-based ROIs were lowest in the caudate nucleus, while the ratios of the I-123 FP-CIT-based ROIs were almost the same throughout all three parts. In contrast, in Parkinsonian patients, the specific binding ratios of the I-123 FP-CIT-based ROIs revealed rostrocaudal decline, while those of the MRI-based ROIs were highest in the anterior putamen. CONCLUSION: We created an ROI template on the anatomically normalized MRI and I-123 FP-CIT images, and concluded that I-123 FP-CIT-based ROIs are more suitable for obtaining quantitative values than MRI-based ones.