TY - JOUR T1 - In Vivo Quantification of Cerebral Translocator Protein Binding in Humans Using 6-Chloro-2-(4′-<sup>123</sup>I-Iodophenyl)-3-(<em>N,N-</em>Diethyl)-Imidazo[1,2-a]Pyridine-3-Acetamide SPECT JF - Journal of Nuclear Medicine JO - J Nucl Med SP - 1966 LP - 1972 DO - 10.2967/jnumed.114.143727 VL - 55 IS - 12 AU - Ling Feng AU - Claus Svarer AU - Gerda Thomsen AU - Robin de Nijs AU - Vibeke A. Larsen AU - Per Jensen AU - Dea Adamsen AU - Agnete Dyssegaard AU - Walter Fischer AU - Per Meden AU - Derk Krieger AU - Kirsten Møller AU - Gitte M. Knudsen AU - Lars H. Pinborg Y1 - 2014/12/01 UR - http://jnm.snmjournals.org/content/55/12/1966.abstract N2 - This study provides the first comprehensive quantification of translocator protein (TSPO) binding using SPECT and 6-chloro-2-(4′-123I-iodophenyl)-3-(N,N-diethyl)-imidazo[1,2-a]pyridine-3-acetamide (123I-CLINDE) in neurologic patients. 123I-CLINDE is structurally related to well-known PET ligands such as 18F-PBR111 and 18F-DPA-714. Methods: Six patients with cerebral stroke and 4 patients with glioblastoma multiforme (GBM) underwent 150-min dynamic SPECT scans with arterial blood sampling. Four of the patients were rescanned. All patients were genotyped for the rs6971 polymorphism. Volumes of interest were delineated on the individual SPECT scans and the coregistered MR images. Compartmental and graphical models using arterial input or the cerebellum as a reference region were used to quantify 123I-CLINDE binding. Results: Among the 6 models investigated, the 2-tissue-compartment model with arterial input described the time–activity data best. Time–stability analyses suggested that acquisition time should be at least 90 min. Intersubject variation in the cerebellar distribution volume (VT) was clearly related to the TSPO genotype. In the stroke patients the VT in the periinfarction zone, compared with VT in the ipsilateral cerebellum, ranged from 1.4 to 3.4, and in the GBM patients the VT in the tumor, compared with the VT in the cerebellum, ranged from 1.8 to 3.4. In areas of gadolinium extravasation, 123I-CLINDE binding parameters were not significantly changed. Thus, 123I-CLINDE binding does not appear to be importantly affected by blood–brain barrier disruption. Conclusion: As demonstrated within a group of stroke and GBM patients, 123I-CLINDE SPECT can be used for quantitative assessment of TSPO expression in vivo. Because of the absence of a region devoid of TSPO, reference tissue models should be used with caution. The 2-tissue-compartment kinetic analysis of a 90-min dynamic scan with arterial blood sampling is recommended for the quantification of 123I-CLINDE binding with SPECT. ER -