Test-retest reproducibility of [(11)C]-l-deprenyl-D(2) binding to MAO-B in the human brain

BACKGROUND: [(11)C]-l-deprenyl-D(2) 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. RESULTS: We performed two [(11)C]-l-deprenyl-D(2) 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 (K (1), k (2), k (3)) using metabolite-corrected plasma radioactivity. The λk (3) defined as (K (1)/k (2)) × k (3) 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 k (3) was 2.6% (medial frontal cortex) to 10.3% (hippocampus), and that of λk (3) was 5.0% (thalamus) to 9.2% (cerebellum). Mean %difference of all regions were 5.3 and 7.0% in k (3) and λk (3), respectively. All regions showed below 10% variabilities except the hippocampus in k (3) (10.3%). Intraclass correlation coefficient (ICC) of k (3) was 0.78 (hippocampus) to 0.98 (medial frontal cortex), and that of λk (3) was 0.78 (hippocampus) to 0.95 (thalamus). Mean ICC were 0.94 and 0.89 in k (3) and λk (3), respectively. The highest positive correlation with age was observed in the hippocampus, as r = 0.75 in k (3) and 0.76 in λk (3). After PVEc, mean %difference were 5.6 and 7.2% in k (3) and λk (3), respectively. Mean ICC were 0.92 and 0.90 for k (3) and λk (3), respectively. These values were almost the same as those before PVEc. CONCLUSIONS: The present results indicate that k (3) and λk (3) of [(11)C]-l-deprenyl-D(2) 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.