Test-retest reproducibility of [11C]-l-deprenyl-D2 binding to MAO-B in the human brain

Abstract

Background[11C]-l-deprenyl-D2 is a positron emission tomography (PET) radioligand for measurement of the monoamine oxidase B (MAO-B) activity in vivo brain. The estimation of the test-retest reproducibility is important for accurate interpretation of PET studies.ResultsWe performed two [11C]-l-deprenyl-D2 scans for six healthy subjects and evaluated the test-retest variability of this radioligand. MAO-B binding was quantified by two tissue compartment model (2TCM) with three rate constants (K1, k2, k3) using metabolite-corrected plasma radioactivity. The λk3 defined as (K1/k2) × k3 was also calculated. The correlation between MAO-B binding and age, and the effect of partial volume effect correction (PVEc) for the reproducibility were also estimated. %difference of k3 was 2.6% (medial frontal cortex) to 10.3% (hippocampus), and that of λk3 was 5.0% (thalamus) to 9.2% (cerebellum). Mean %difference of all regions were 5.3 and 7.0% in k3 and λk3, respectively. All regions showed below 10% variabilities except the hippocampus in k3 (10.3%). Intraclass correlation coefficient (ICC) of k3 was 0.78 (hippocampus) to 0.98 (medial frontal cortex), and that of λk3 was 0.78 (hippocampus) to 0.95 (thalamus). Mean ICC were 0.94 and 0.89 in k3 and λk3, respectively. The highest positive correlation with age was observed in the hippocampus, as r = 0.75 in k3 and 0.76 in λk3. After PVEc, mean %difference were 5.6 and 7.2% in k3 and λk3, respectively. Mean ICC were 0.92 and 0.90 for k3 and λk3, respectively. These values were almost the same as those before PVEc.ConclusionsThe present results indicate that k3 and λk3 of [11C]-l-deprenyl-D2 are reliable parameters for test-retest reproducibility with healthy subjects both before and after PVEc. The studies with patients of larger sample size are required for further clinical applications.