A comparison of F-18-dopa PET and inversion recovery MRI in the diagnosis of Parkinson's disease

Objective: To quantify structural changes in the substantia nigra of patien ts with PD with inversion recovery MRI and to compare these with striatal d opaminergic function measured with F-18-dopa PET. Methods: The authors stud ied 10 patients with PD and eight age-matched control subjects with a combi nation of MR sequences previously reported to be sensitive to nigral cell l oss. Striatal regions of interest were defined on T1-weighted MRI coregiste red to F-18-dopa PET in all subjects. Results: Discriminant function analys is of the quantified MR nigral signal correctly classified 83% of the combi ned PD patient/control group; three of 10 PD cases were incorrectly classif ied as "normal" (Wilks' lambda = 0.724, p > 0.05). Discriminant function an alysis correctly classified 100% of PD patients and control subjects with F -18-dopa PET based on mean caudate and putamen K-i values (Wilks' lambda = 0.065, p < 0.001). Correlations between mean putamen K-i and rostral and ca udal nigral MR signal changes and mean caudate K-i and caudal nigral MR sig nal changes were found (r = -0.76, -0.69, -0.80, p < 0.05). Conclusion: F-1 8-dopa PET is more reliable than inversion recovery MRI in discriminating p atients with moderately severe PD from normal subjects. However, the struct ural changes detected within the substantia nigra of patients with PD found using inversion recovery MRI correlate with measures of striatal dopaminer gic function using F-18-dopa PET.