Test‐retest variability of relative tracer delivery rate as measured by [ 11 C]PiB

Background In Alzheimer’s disease (AD), reductions in cerebral blood flow (CBF) have been reported and these may be used as proxy for measuring treatment efficacy or progression. The gold standard technique CBF is [15O]H2O positron emission tomography (PET). Recent studies, however, high correlations between [11C]PiB PET derived relative tracer delivery rate R 1 CBF, suggesting that a good of CBF. As longitudinal studies become more common progression, it important to know the intrinsic variability 1. purpose present study was determine test-retest (TRT) variability. Method Previously, TRT binding potential has group twelve participants (five cognitively unimpaired (CU), one with mild cognitive impairment six AD dementia), which all underwent two 90 min scans using Siemens ECAT EXACT HR+ scanner1. This dataset reanalysed also R1. voxel-based implementation two-step simplified reference tissue model cerebellar grey matter generate R1 images. Next, calculated both globally regionally, global measures were compared diagnostic groups non-parametric Mann-Whitney U test. correlation analysis assess relationship regional volume. Finally, test retest Linear Mixed Effect Models Bland-Altman analysis. Result Global (R1) significantly lower patients (test R1:0.82±0.04, R1:0.82±0.03) CU R1:0.93±0.04 R1:0.91±0.03, p<0.01). low across regions (range:1.5-5.8%), trend effect towards smaller larger (R2=0.14, p=0.09). Furthermore, showed high, significant (R2=0.92, slope=0.98) negligible bias (0.69±3.07%). Conclusion precision suggests suitable applicability cross-sectional studies. finding further demonstrates utility dynamic dual-biomarker imaging research. Reference: Tolboom et al.(2009) Eur J Nucl Med Mol Imaging 36:1629-38.