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

Abstract

ObjectiveNewly 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]-4-11C-methoxy-N-methylbenzamide (11C-ITMM) with the existing marker, fluorine-18-labeled fluorodeoxyglucose (18F-FDG) imaging, in the cerebellum. MethodsFourteen subjects consisting of 12 patients with cerebellar ataxia and two healthy subjects underwent 11C-ITMM and 18F-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 (BPND) was calculated to estimate mGluR1 availability using the white matter as a reference region. 18F-FDG uptake was normalized using the white matter (FUwm). ResultsThere were significant positive correlations between the BPND and FUwm values in the anterior lobe (r=0.83, P<0.001), posterior lobe (r=0.69, P=0.009), and vermis (r=0.58, P=0.042). Regarding the relationship of SARA scores with the BPND and FUwm values, a significant negative correlation was found only in the anterior lobe between the SARA scores and BPND values (r=−0.64, P=0.029). ConclusionThis study showed that mGluR1 imaging was comparable to 18F-FDG imaging in the cerebellum. However, mGluR1 imaging was more strongly associated with the SARA scores than 18F-FDG imaging was, suggesting that mGluR1 imaging can be a more specific technique than 18F-FDG imaging for evaluating cerebellar ataxia.