RT Journal Article SR Electronic T1 18F-FET-PET/MR-guided biopsies of contrast-enhancing gliomas: a prospective study JF Journal of Nuclear Medicine JO J Nucl Med FD Society of Nuclear Medicine SP 3115 OP 3115 VO 63 IS supplement 2 A1 Maciej Harat A1 Bogdan Malkowski A1 Józefina Rakowska A1 Marek Harat A1 Iza Miechowicz A1 Jacek Furtak A1 Lukasz Szylberg YR 2022 UL http://jnm.snmjournals.org/content/63/supplement_2/3115.abstract AB 3115 Introduction: MRi- guided stereotactic biopsy is a gold standard for diagnosis of unresectable high grade glioma. A prospective study was planned to assessed whether PET-guided biopsies were more accurate than MRI-based. Also to examine the value of early FET-PET acquisition for the identification of high grade foci not associated with contrast enhancement.Methods: Twenty-three patients were enrolled in this study due to suspected high grade glioma. Patients meeting the inclusion criteria were referred for dual time point 18F-FET PET-MRI.  Biopsies were planned based on early FET-PET acquisition 5-15 minutes post tracer injection. The following biopsy sites were determined in each case: (i) site of contrast enhancement and increased FET uptake (ii) contrast enhancement but no increase in FET uptake; (iii) increased FET uptake but without contrast enhancement; and (iv) peripheral areas hyperintense in T2 FLAIR without increased FET uptake and contrast enhancement. Results: In 35% cases, the biopsy result was changed to a higher tumor grade after the inclusion of FET-positive sites. In all cases, high FET uptake was visualized and confirmed outside areas of contrast enhancement on MRI, indicative of high-grade glioma. Results from biopsies based on the FLAIR sequences corresponded to neoplastic lesions in 13 cases (57%), most often with a lower grade than in areas of high FET uptakeConclusions: Early FET-PET can be used to locate the most malignant areas of contrast enhancing gliomas. Treatment or biopsy planning based solely on MRI images may miss some areas of glioma. Brain areas hyperintense in T2 FLAIR are not specific for malignancy.