Reduction in variability of dopamine transporter measures using SPECT and ultra-high-resolution fan beam collimators: comparison with parallel-hole collimators in healthy controls for a clinical reference database

Purpose The purpose of this study was to create 123 I-FP-CIT reference values for ultra-high-resolution fan beam collimators (UHR-FB) from a sample of subjects without dopaminergic degeneration and to compare them to a normal database -PPMI database- of a commercial software (DaTQUANT) obtained using high-resolution parallel-hole collimators (HR-PH). Methods A striatal phantom study was performed to compare UHR-FB with HR-PH and to obtain a correction factor between collimators. Normal 123 I-FP-CIT studies from 177 subjects acquired using UHR-FB were retrospectively selected on the basis of visual and semi-quantitative analysis as well as of the neurological follow-up (range of 2–9 years). SPECT images were reconstructed using the same parameters of DaTQUANT normal database and SBR values were obtained for striatal structures. Correction factor was applied to the UHR-FB database to test differences against DaTQUANT database. Results Correction factor obtained from the phantom study was 0.84. Uncorrected SBR values of the local database were significantly higher than PPMI database values, but no significant differences were found using corrected values. Coefficients of variations of SBR values were significantly lower in a local database than PPMI database (15% vs 20%). Significant effects of age on SBR were observed in both databases with a reduction rate for a decade of 6% in the PPMI database and 4.5% in the local database. In the latter, women had slightly higher SBR values and a steeper decline with advancing age compared to men, whereas no significant gender differences were found in the PPMI database. Conclusion The SBR values obtained using UHR-FB have an age-related distribution comparable to that of healthy subjects but with lower variability. The reduction rate per decade was similar between the two databases but the gender effect was found only in the local database, probably related to the better performance of UHR-FB.