Characterization of brain lesions using MRI/spectroscopy versus FDG PET fused with MRI

Abstract

Objectives: To retrospectively compare the diagnostic value of MRI with integrative spectroscopy (MRI/spec), to anatomically fused FDG PET/MRI (PET/MRI) in brain lesions.

Methods: Twenty-four patients (n= 27 brain lesions) underwent MRI/spec (LX 1.5T, GE; Achieva 3.0T, Philips) and standard FDG PET/CT including the brain (Gemini or GeminiTF, Philips) within a 3-month period. Transaxial MRI and PET images of the brain were fused using Extended Brilliance workstation (Philips). Histopathology or imaging follow-up served as reference standard. Group A (21 lesions): metastatic lesions or grade III/IV primary brain tumors; group B (6 lesions): grade I/II primary brain tumors or non-tumor lesions. PET criteria: Increased uptake in the center or periphery of the lesion was group A, otherwise group B. MRI/spec criteria: based on prior reading in reports.

Results: MRI/spec and PET/MRI characterized 20/27 (74%) and 23/27 (85%) lesions correctly, and 5/27 (19%) and 4/27 (15%) lesions incorrectly. Findings of combined MRI/spec and PET/MRI are summarized in a table. Conclusions: Due to its detailed anatomical information, MRI/spec is better than PET/MRI in detecting and characterizing lesions < 2 cm. However, PET/MRI appears to characterize lesions > 2 cm better than MRI/spec because of the high specificity of FDG PET for high-grade tumors. PET/MRI can have added value in lesions that are being interpreted as indeterminate by MRI/spec.