MRI-PET

Multimodal Imaging in Malignant Brain Tumors: Enhancing the Preoperative Risk Evaluation for Motor Deficits with a Combined Hybrid MRI-PET and Navigated Transcranial Magnetic Stimulation Approach

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Editor’s Comment

Patients with malignant brain tumors involving the central region underwent a hybrid O-(2-[18F]fluoroethyl)-L-tyrosine–PET-MR imaging and motor mapping by neuronavigated transcranial magnetic stimulation. The spatial relationship between functional tissue and lesion volumes as depicted by structural and metabolic imaging was analyzed. Tumor infiltration of the M1 region or the corticospinal tract as depicted by FET-PET is highly indicative of motor impairment, better than contrast-enhanced T1WI alone, and is of predictive value for operative-risk evaluation.

Abstract

BACKGROUND AND PURPOSE

Motor deficits in patients with brain tumors are caused mainly by irreversible infiltration of the motor network or by indirect mass effects; these deficits are potentially reversible on tumor removal. Here we used a novel multimodal imaging approach consisting of structural, functional, and metabolic neuroimaging to better distinguish these underlying causes in a preoperative setting and determine the predictive value of this approach.

MATERIALS AND METHODS

Thirty patients with malignant brain tumors involving the central region underwent a hybrid O-(2-[18F]fluoroethyl)-L-tyrosine–PET-MR imaging and motor mapping by neuronavigated transcranial magnetic stimulation. The functional maps served as localizers for DTI tractography of the corticospinal tract. The spatial relationship between functional tissue (motor cortex and corticospinal tract) and lesion volumes as depicted by structural and metabolic imaging was analyzed.

RESULTS

Motor impairment was found in nearly all patients in whom the contrast-enhanced T1WI or PET lesion overlapped functional tissue. All patients who functionally deteriorated after the operation showed such overlap on presurgical maps, while the absence of overlap predicted a favorable motor outcome. PET was superior to contrast-enhanced T1WI for revealing a motor deficit before the operation. However, the best correlation with clinical impairment was found for T2WI lesion overlap with functional tissue maps, but the prognostic value for motor recovery was not significant.

CONCLUSIONS

Overlapping contrast-enhanced T1WI or PET-positive signals