Simplified quantification of FDDNP PET studies

Objectives To investigate the use of standardized uptake value ratio (SUVR) over short time intervals of FDDNP PET scans for the classification between control subjects and patients with Alzhiemer’s disease (AD).

Methods Imaging studies were performed on 9 control subjects and 12 AD patients. Following ~10 mCi bolus injection of FDDNP, dynamic PET scans were acquired in 3D mode for 125 min with an ECAT HR+ scanner. Head movement correction was applied prior to defining regions of interest on the summed image of early frames. Regions included frontal, parietal, medial temporal, lateral temporal, posterior cingulate and cerebellum (CBL). The SUVR (to CBL) was computed for various time intervals. The SUVRs were compared with distribution volume ratio (DVR) estimates derived by Logan analysis (35-125 min) with CBL as the reference region. Discriminant analysis was conducted on the regional DVRs and SUVRs of different time intervals to compare classification and prediction performance in discriminating controls from ADs.

Results Good correlation was observed between regional DVRs and SUVRs obtained with 35-65 min (R2=0.89-0.94), 35-55 min (R2=0.87-0.93), 45-65 min (R2=0.80-0.88) and 45-55 min (R2=0.82-0.87) intervals, despite the SUVRs generally overestimated DVR (~45%). Discriminant analysis showed that SUVRs of 35-65, 45-65 and 45-55 min intervals provided the same performance of classification accuracy (95%), sensitivity (92%) and specificity (100%) between controls and ADs as compared to that obtained with DVR.

Conclusions The 45-55 min SUVR is practical for quantification of FDDNP PET studies, as it provided overall good agreement with Logan DVR (that needs dynamic scans) and required only 10 min of static scan that is expected to be better tolerated by the subjects under study and less prone to movement artifacts.

Research Support NIH grant P01-AG02583