Components Determination in Hypoxic Glioblastoma Measured with 18F-FMISO PET imaging

Tumor hypoxia is defined as the reduction of oxygen supply to tumor cells. Glioblastoma (GBM) tumors are characterized by high levels of hypoxia, which results in poor prognosis even after treatment by radiotherapy and chemotherapy. The most current technique used for imaging hypoxia in GBM is 18F-Fluoromisonidazole (18F-FMISO) with PET imaging. The aim of this study is to decompose the dynamic 18F-FMISO images in tissue components and to study the spatial distribution of GBM in the tumor over time. The scanning protocol begins with 15 or 30 minutes dynamic images of the brain followed by static images at 2 h, 3 h and 4 h. We used spectral analysis technique to decompose the whole 3D dynamic image into its components in order to isolate the hypoxic regions. The results show non-uniformity in tumor shape as a function of time. The tumor becomes uniform after 2 h resembling its shape on MRI image, even though, a difference in shape has been found with later frames. Some tumor regions show accumulative response while others, even appearing with comparable uptake of 18F-FMISO, they were not observed as hypoxic based on the results of spectral analysis. Clearly, blood volume, hypoxic and perfused tissues and even necrotic regions can be isolated and studied separately. Therefore, the pattern of changes in tumor shape over time can be explained for a better tumor treatment.