Complementary but Distinct Roles for MRI and 18F-Fluoromisonidazole PET in the Assessment of Human Glioblastomas

摘要

Glioblastoma multiforme is a primary brain tumor known for its rapid proliferation, diffuse invasion, and prominent neovasculature and necrosis. This study explores the in vivo link between these characteristics and hypoxia by comparing the relative spatial geometry of developing vasculature inferred from gadolinium-enhanced T1-weighted MRI (T1Gd), edematous tumor extent revealed on T2-weighted MRI (T2), and hypoxia assessed by ¹⁸F-fluoromisonidazole PET (¹⁸F-FMISO). Given the role of hypoxia in upregulating angiogenic factors, we hypothesized that the distribution of hypoxia seen on ¹⁸F-FMISO is correlated spatially and quantitatively with the amount of leaky neovasculature seen on T1Gd.MethodsA total of 24 patients with glioblastoma underwent T1Gd, T2, and ¹⁸F-FMISO—11 studies preceded surgical resection or biopsy, 7 followed surgery and preceded radiation therapy, and 11 followed radiation therapy. Abnormal regions seen on the MRI scan were segmented, including the necrotic center (T0), the region of abnormal blood–brain barrier associated with disrupted vasculature (T1Gd), and infiltrating tumor cells and edema (T2). The ¹⁸F-FMISO images were scaled to the blood ¹⁸F-FMISO activity to create tumor-to-blood ratio (T/B) images. The hypoxic volume (HV) was defined as the region with T/Bs greater than 1.2, and the maximum T/B (T/Bmax) was determined by the voxel with the greatest T/B value.