Simplified quantification and reproducibility studies of dopamine D2-receptor binding with iodine-123-IBF SPECT in healthy subjects.

Abstract

The purpose of this study was to assess the feasibility of a simplified SPECT scan protocol to quantify D2-receptor binding using [123I]iodobenzofuran (IBF) and to evaluate reproducibility of quantitative IBF-SPECT imaging without blood data. Twenty healthy volunteers participated in the study, six had test/retest studies separated by 1 wk. Scans were acquired every 5 min for 180 min using a triple-headed SPECT camera after a bolus injection of IBF (292 MBq). The receptor parameter was determined by using our previously proposed variation of graphical analysis that derives the distribution volume ratio (Rv = V3/V2) from multiple scan data without blood data. Rv' was determined from three 20-min scan data obtained at 0-20, 50-70 and 160-180 min postinjection and compared with Rv as determined from scans obtained at 0-180 min. The mean Rv' (2.93 +/- 0.59) underestimated the mean Rv (3.10 +/- 0.50) by 5%. The mean variability (mean percent absolute difference) between Rv' and Rv was low (10%) with excellent reliability (intraclass correlation coefficient, p = 0.90). The relationship between Rv' and Rv was linear (r = 0.95, p < 10(-5)). The mean test/retest Rv and mean test/retest Rv' were (3.19 +/- 0.70/3.18 +/- 0.80) and (3.16 +/- 0.81/3.01 +/- 0.94), respectively, and these measures were not significantly different between test/retest studies. The mean test/retest variability of Rv was low (5%) with excellent reliability (p = 0.98). In addition, the mean test/retest variability of Rv' was low (10%) with excellent reliability (p = 0.94). Three short (20 min) IBF-SPECT scans allowing for rest periods between scans permit reliable measurements of the dopamine D2-receptor parameter V3/V2. Quantitative IBF-SPECT imaging without blood data is reliable and reproducible.