11c-methionine PET combined with advanced MRI for the preoperative evaluation of suspected diffuse low-grade gliomas

• PURPOSE: To evaluate positron emission tomography (PET) with the tracer 11C-methionine (MET) combined with perfusion- and diffusion MRI (pMRI and dMRI) for the preoperative evaluation of patients with suspected diffuse low-grade gliomas (DLGG).MATERIALS AND METHODS: In this prospective study with institutional review board approval, 25 patients with suspected DLGG in cortical structures (n=24) were examined with 11C-methionine PET (MET PET), pMRI and dMRI. The hot spot (HS) in the tumor, i.e. the area with highest MET uptake, was used as a reference region for evaluating maximum relative cerebral blood volume (rCBVmax) and minimum apparent diffusion coefficient values (ADCmin) by MRI. The concordance between MET PET, pMRI and dMRI, as single parameters and combined, was assessed with respect to histological tumor diagnosis, which was available for 18 patients.RESULTS: In all but one patient tumor diagnosis was confirmed. The region showing highest rCBVmax corresponded with the HS region identified by MET PET in all cases, and a positive correlation between MET uptake and rCBVmax was found (Spearman: r=0.67, P < 0.0001). The concordance between MET uptake and rCBVmax in predicting malignancy grade of gliomas was 67%. MET uptake in the HS was inversely correlated with ADCmin values measured in this region (Spearman: r=-0.54, p < 0.005).CONCLUSION: MET PET combined with advanced MRI facilitates the identification of specific regions of interest for histological tumor diagnosis and thereby provides a powerful tool in the preoperative evaluation of DLGG.

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