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]-4-¹¹C-methoxy-N-methylbenzamide (¹¹C-ITMM) with the existing marker, fluorine-18-labeled fluorodeoxyglucose (¹⁸F-FDG) imaging, in the cerebellum.

Methods: Fourteen 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 (BP_ND) was calculated to estimate mGluR1 availability using the white matter as a reference region. ¹⁸F-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<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 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 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.

Keywords: (11)C-ITMM; (18)F-FDG; Cerebellar ataxia; PET; Type 1 metabotropic glutamate receptor.