Comparison of imaging using 11C-ITMM and 18F-FDG for the detection of cerebellar ataxia

Abstract Objective Newly developed methods for imaging type 1 metabotropic glutamate receptor (mGluR1) have the potential use for estimating cerebellar function. We aimed to compare mGluR1 imaging using N -[4-[6-(isopropylamino)pyrimidin-4-yl]-1,3-thiazol-2-yl]-4- 11 C-methoxy- N -methylbenzamide ( 11 C-ITMM) with the existing marker, fluorine-18-labeled fluorodeoxyglucose ( 18 F-FDG) imaging, in the cerebellum. Methods Fourteen subjects consisting of 12 patients with cerebellar ataxia and two healthy subjects underwent 11 C-ITMM and 18 F-FDG positron emission tomography. The degree of ataxia was scored with the Scale for the Assessment and Rating of Ataxia (SARA). Volumes-of-interest were placed on the anterior and posterior lobes and vermis. The binding potential ( BP ND ) was calculated to estimate mGluR1 availability using the white matter as a reference region. 18 F-FDG uptake was normalized using the white matter ( FU wm ). Results There were significant positive correlations between the BP ND and FU wm values in the anterior lobe ( r  = 0.83, P r  = 0.69, P  = 0.009), and vermis ( r  = 0.58, P  = 0.042). Regarding the relationship of SARA scores with the BP ND and FU wm values, a significant negative correlation was found only in the anterior lobe between the SARA scores and BP ND values ( r  = − 0.64, P  = 0.029). Conclusion This study showed that mGluR1 imaging was comparable to 18 F-FDG imaging in the cerebellum. However, mGluR1 imaging was more strongly associated with the SARA scores than 18 F-FDG imaging was, suggesting that mGluR1 imaging can be a more specific technique than 18 F-FDG imaging for evaluating cerebellar ataxia.