Abstract
123I-iodobenzovesamicol (123I-IBVM) is a Single Photon Emission Computed Tomography (SPECT) selective radioligand for the vesicular acetylcholine transporter (VAChT), used to assess the integrity of cholinergic pathways in various neurological disorders. The current noninvasive method for quantitative analysis of 123I-IBVM, based on a reference tissue modeling (MRTM2), requires repeated scans for several hours, limiting its application in clinical trials. The objective is to validate a simplified acquisition method based on a single 123I-IBVM static scan preserving the quantification accuracy. Three acquisition times were tested comparatively to a kinetic analysis using MRTM2. Methods: Six healthy volunteers underwent a dynamic SPECT acquisition comprising of 14 frames over 28 h and a magnetic resonance imaging (MRI) scan. MR images were automatically segmented, providing the volumes of 19 regions of interest (ROI). SPECT dataset were co-registered with MR images and regional time-activity curves were derived. For each ROI, a complete MRTM2 pharmacokinetic analysis, using the cerebellar hemispheres as reference region, led to the calculation of an 123I-IBVM to VAChT binding parameter, the nondisplaceable binding potential (BPND-MRTM2). A simplified analysis was also performed at t = 5 h, 8 h and 28 h after injection, providing simplified BPND, given as BPND-t = CROI-Ccerebellar hemispheres/Ccerebellar hemispheres, with C = averaged radioactive concentration. Results: No significant difference was found between BPND-5h, BPND-8h and BPND-MRTM2 in all extra-striatal regions explored regions. BPND-28h were significantly higher than BPND-5h, BPND-8h and BPND-MRTM2 in 9 out of the 18 regions explored (p<0.05). BPND-5h, BPND-8h and BPND-28h were significantly correlated with BPND-MRTM2 (p<0.05; rho = 0.99, 0.98 and 0.92 respectively). In the striatum, BPND-28h were significantly higher than BPND-5h and BPND-8h. BPND-5h differed significantly from BPND-MRTM2 (p<0.05), with BPND-5h being 43.6% lower. Conclusion: In the extra-striatal regions, a single scan acquisition at t = 5 h or t = 8 h after injection provides quantitative results similar to a pharmacokinetic analysis. However, with the highest correlation and accuracy, t = 5 h is the most suitable time to perform an accurate 123I-IBVM quantification. In the striatum, none of the three times has led to an accurate quantification.
- Neurology
- Radiotracer Tissue Kinetics
- SPECT/CT
- SPECT
- VAChT
- [123I]-IBVM
- neurological disorders
- single scan acquisition
- Copyright © 2015 by the Society of Nuclear Medicine and Molecular Imaging, Inc.