Simultaneous FET-PET and contrast-enhanced MRI based on hybrid PET/MR improves delineation of tumor spatial biodistribution in gliomas: a biopsy validation study

Abstract

Purpose Glioma treatment planning requires precise tumor delineation, which is typically performed with contrast-enhanced (CE) MRI. However, CE MRI fails to reflect the entire extent of glioma. O-(2-18 F-fluoroethyl)-L-tyrosine (18 F-FET) PET may detect tumor volumes missed by CE MRI. We investigated the clinical value of simultaneous FET-PET and CE MRI in delineating tumor extent before treatment planning. Guided stereotactic biopsy was used to validate the findings. Methods Conventional MRI and 18 F-FET PET were performed simultaneously on a hybrid PET/MR in 33 patients with histopathologically confirmed glioma. Tumor volumes were quantified using a tumor-to-brain ratio ≥ 1.6 (V PET) and a visual threshold (V CE). We visually assessed abnormal areas on FLAIR images and calculated Dice's coefficient (DSC), overlap volume (OV), discrepancy-PET, and discrepancy-CE. Additionally, several stereotactic biopsy samples were taken from "matched" or "mismatched" FET-PET and CE MRI regions. Results Among 31 patients (93.94%), FET-PET delineated significantly larger tumor volumes than CE MRI (77.84 ± 51.74 cm 3 vs. 34.59 ± 27.07 cm 3 , P < 0.05). Of the 21 biopsy samples obtained from regions with increased FET uptake, all were histopathologically confirmed as glioma tissue or tumor infiltration, whereas only 13 showed enhancement on CE MRI. Among all patients, the spatial similarity between V PET and V CE was low (average DSC 0.56 ± 0.22), while the overlap was high (average OV 0.95 ± 0.08). The discrepancy-CE and discrepancy-PET were lower than 10% in 28 and 0 patients, respectively. Eleven patients showed V PET partially beyond abnormal signal areas on FLAIR images. Conclusion The metabolically active biodistribution of gliomas delineated with FET-PET significantly exceeds tumor volume on CE MRI, and histopathology confirms these findings. Our preliminary results indicate that combining the anatomic and Shuangshuang Song and Ye Cheng contributed equally to this work. This article is part of the Topical Collection on Oncology-Brain.

PET/MR in recurrent glioblastoma patients treated with regorafenib: [18F]FET and DWI-ADC for response assessment and survival prediction

“… 28 The chosen cut-off has been subsequently used successfully in a number of publications presenting histopathological confirmation and/or MR comparisons. 29,30 The derived segmented volume was visually refined to exclude areas of non-specific [ 18 F]FET spillover (major blood vessels, cranial bones, meninges etc.) using the aligned MDC images as the morphological reference.…”

Benefit of Static FET PET in Pretreated Pediatric Brain Tumor Patients with Equivocal Conventional MRI Results

“…Further development of hybrid PET/MR scanners enabled simultaneous recording of anatomical and functional images using perfusion and diffusion weighted imaging in addition to metabolic imaging [14]. Song et al demonstrated when using hybrid FET-PET/MRI that FET-PET delineated histologically proven primary or recurrent tumor volume outside contrast enhancement on MRI, adding vital information for treatment planning (e. g. biopsy, resection, radiation) [26]. Marner et al showed an increased specificity when employing hybrid FET-PET/MRI in early postoperative detection of residual tumor tissue in pediatric brain tumor patients compared to MRI alone [17].…”

Glioma Imaging by O-(2-18F-Fluoroethyl)-L-Tyrosine PET and Diffusion-Weighted MRI and Correlation With Molecular Phenotypes, Validated by PET/MR-Guided Biopsies

“…Patients had undergone the integrated PET/MRI within one week before the surgical procedure. To analyze the images, we used our previously published image-processing method ( 21 ). 18 F-FET PET and MRI data were postprocessed and analyzed using PMOD version 3.505 (PMOD Ltd.).…”