Test-retest reproducibility of the parkinsonism-related metabolic pattern (PRP) in drug-naive parkinsonian macaques: A study with FDG PET

Objectives Using FDG PET, we have previously reported the presence of a parkinsonism-related metabolic pattern (PRP) in both patients with Parkinson’s disease (PD) and in macaques following MPTP administration. In this study, we examined whether PRP can be reliably measured with a clinical PET scanner in an untreated cohort of animals undergoing systemic MPTP injection.

Methods FDG PET scans were obtained at baseline and three months on a Siemens PET/CT camera in two normal cynomolgus macaques and in three MPTP-lesioned macaques. Images were acquired between 40-80 min postinjection (5×8 min frames) and reconstructed with both FBP and OSEM iterative methods. Network expression of PRP was computed for all animals on a voxel basis using spatial covariance analysis. Changes in PRP expression were assessed between the animal groups and over two time points.

Results The PRP expression was elevated in the MPTP-lesioned animals relative to the controls at both baseline and follow-up (p<0.0001). PRP scores in all animals were stable over the two time points and did not different from those used originally to derive the PRP. The PRP expression increased from 40 to 80 min postinjection, especially in the MPTP-lesioned animals. Mean RPR scores showed slightly higher test-retest reliability over 60-80 min than over 40-60 min postinjection.

Conclusions The expression of an abnormal metabolic pattern can be reliably quantified in parkinsonian monkeys. The PRP was higher in MPTP-lesioned macaques than in controls and remained stable over 3 months. FDG PET imaging and spatial covariance analysis may be a valuable tool for quantifying changes in regional brain function, and drug action, in experimental animal models of parkinsonism.

Research Support The Cure Parkinson’s Trust and the Krembil Foundatio