Metabolic striatal volume analysis using isocontour VOI method in F-18 FP-CIT PET

Objectives We applied a simple isocontour VOI method to analyze whole striatum in F-18 FP-CIT PET image and investigate the usefulness of the method in differentiating healthy subjects from idiopathic Parkinson’s diseases (IPD) patients and the correlation with various severity of motor symptoms in patients with IPD.

Methods Forty-three IPD patients (M = 20, 67.8 ± 5.8 years) and 23 age-matched normal subjects underwent F-18 FP-CIT PET. PET images were acquired at 3 hours after administration of radiotracer. Using dedicated workstation, VOIs for whole striatum were drawn automatically and gradient method was used to delineate the metabolic margin. Occipital area was used as reference site. Metabolic volume (MV), striatal volume activity (SVA, metabolic volume x SUVmean) and volume specific uptake ratio (VSUR) were calculated in all subjects and the metabolic parameters were compared between IPD patients and normal subjects. To determine the difference in accuracy between several volumetric parameters, receiver operating characteristic (ROC) curve analysis was done. In IPD patients, equivalent levodopa dose, H & Y stage, resting and kinetic tremor, rigidity, and bradykinesia were evaluated and the correlation between the clinical factor and the metabolic parameters was assessed.

Results MV (14.9 cm3 vs 19.0 cm3), SVA (81.7 vs 166.5) and VSUR (6.0 vs 10.7) were significantly lower in IPD patients than those of normal subjects (p < 0.05). The areas of under of the ROC curve were 0.92 (p < 0.001) for SUVmax, 0.95 (p <0.001) for SUVmean, 0.86 (p < 0.001) for MV, 0.99 (p < 0.001) for SVA, 0.98 (p < 0.001) for SSB and 0.94 (p < 0.001). In patients with IPD, moderate negative correlation was revealed between SVA and H & Y stage (r = -0.50, p = 0.002), VSUR and H & Y stage (r = -0.51, p = 0.002), and MV and bradykinesia (r = -0.43, p = 0.013), and SVA and bradykinesia (r = -0.45, p = 0.008). Linear regression analysis showed significant correlation between equivalent levodopa dose and metabolic volume parameters (R2 = 0.10, p < 0.0001).

Conclusions Metabolic volumetric method using a simple isocontour VOI delineation for whole striatum showed clearly the metabolic difference between healthy subjects and IPD patients; all metabolic volume parameters were significantly decreased in patients group. In addition, the parameters had relatively good correlation with some motor functions; therefore, this simple volumetric analysis method was not only easily usable but proper in quantification.