title: Simplified Quantification Method for In Vivo SPECT Imaging of the Vesicular Acetylcholine Transporter with 123I-Iodobenzovesamicol.
abstract: (123)I-iodobenzovesamicol is a SPECT radioligand selective for the vesicular acetylcholine transporter (VAChT) and used to assess the integrity of cholinergic pathways in various neurologic disorders. The current noninvasive method for quantitative analysis of (123)I-iodobenzovesamicol, based on multilinear reference tissue model 2 (MRTM2), requires repeated scans for several hours, limiting its application in clinical trials. Our objective was to validate a simplified acquisition method based on a single (123)I-iodobenzovesamicol 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 14 frames over 28 h and an MR imaging scan. MR images were automatically segmented, providing the volumes of 19 regions of interest (ROIs). SPECT datasets were coregistered with MR images, and regional time-activity curves were derived. For each ROI, a complete MRTM2 pharmacokinetic analysis, using the cerebellar hemispheres as the reference region, led to the calculation of a (123)I-iodobenzovesamicol-to-VAChT binding parameter, the nondisplaceable binding potential (BP(ND-MRTM2)). A simplified analysis was also performed at 5, 8, and 28 h after injection, providing a simplified BP(ND), given as BP(ND-t) = C(ROI) - C(cerebellar hemispheres)/C(cerebellar hemispheres), with C being the averaged radioactive concentration.
  
  
  RESULTS
  No significant difference was found among BP(ND-5 h), BP(ND-8 h), and BP(ND-MRTM2) in any of the extrastriatal regions explored. BP(ND-28 h) was significantly higher than BP(ND-5 h), BP(ND-8 h), and BP(ND-MRTM2) in 9 of the 17 regions explored (P < 0.05). BP(ND-5 h), BP(ND-8 h), and BP(ND-28 h) correlated significantly with BP(ND-MRTM2) (P < 0.05; ρ = 0.99, 0.98, and 0.92, respectively). In the striatum, BP(ND-28 h) was significantly higher than BP(ND-5 h) and BP(ND-8 h). BP(ND-5 h) differed significantly from BP(ND-MRTM2) (P < 0.05), with BP(ND-5 h) being 43.6% lower.
  
  
  CONCLUSIONS
  In the extrastriatal regions, a single acquisition at 5 or 8 h after injection provides quantitative results similar to a pharmacokinetic analysis. However, with the highest correlation and accuracy, 5 h is the most suitable time to perform an accurate (123)I-iodobenzovesamicol quantification. In the striatum, none of the 3 times has led to an accurate quantification.
authors.affiliation: University of Bordeaux, INCIA, UMR 5287, Bordeaux, France CNRS, INCIA, UMR 5287, Bordeaux, France Service de Médecine Nucléaire, CHU de Bordeaux, Bordeaux, France; and joachim.mazere@chu-bordeaux.fr.
authors.forename: Joachim
authors.initials: J
authors.lastname: Mazère
authors.affiliation: University of Bordeaux, INCIA, UMR 5287, Bordeaux, France CNRS, INCIA, UMR 5287, Bordeaux, France.
authors.forename: Willy
authors.initials: W
authors.lastname: Mayo
authors.affiliation: University of Bordeaux, INCIA, UMR 5287, Bordeaux, France CNRS, INCIA, UMR 5287, Bordeaux, France.
authors.forename: Guillaume
authors.initials: G
authors.lastname: Pariscoat
authors.affiliation: University of Bordeaux, INCIA, UMR 5287, Bordeaux, France CNRS, INCIA, UMR 5287, Bordeaux, France.
authors.forename: Jürgen
authors.initials: J
authors.lastname: Schulz
authors.affiliation: University of Bordeaux, INCIA, UMR 5287, Bordeaux, France CNRS, INCIA, UMR 5287, Bordeaux, France Service de Médecine Nucléaire, CHU de Bordeaux, Bordeaux, France; and EPHE, Paris, France.
authors.forename: Michele
authors.initials: M
authors.lastname: Allard
authors.affiliation: University of Bordeaux, INCIA, UMR 5287, Bordeaux, France CNRS, INCIA, UMR 5287, Bordeaux, France Service de Médecine Nucléaire, CHU de Bordeaux, Bordeaux, France; and.
authors.forename: Philippe
authors.initials: P
authors.lastname: Fernandez
authors.affiliation: University of Bordeaux, INCIA, UMR 5287, Bordeaux, France CNRS, INCIA, UMR 5287, Bordeaux, France Service de Médecine Nucléaire, CHU de Bordeaux, Bordeaux, France; and.
authors.forename: Frédéric
authors.initials: F
authors.lastname: Lamare
mesh_terms: D000368:Aged; D001921:Brain / Q000000981:diagnostic imaging; D064368:Healthy Volunteers; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007457:Iodine Radioisotopes; D008279:Magnetic Resonance Imaging; D064847:Multimodal Imaging; D010880:Piperidines; D012016:Reference Values; D015203:Reproducibility of Results; D013997:Time Factors; D015899:Tomography, Emission-Computed, Single-Photon / Q000379:methods*; D014057:Tomography, X-Ray Computed; D050494:Vesicular Acetylcholine Transport Proteins / Q000378:metabolism*
chemical_list: D007457:Iodine Radioisotopes; D010880:Piperidines; D050494:Vesicular Acetylcholine Transport Proteins
keywords: 123I-IBVM; SPECT; VAChT; neurological disorders; single scan acquisition