Abstract
PurposeThe aim of this study is to compare the diagnostic accuracy of amino acid PET, MR perfusion and diffusion as stand-alone modalities and in combination in identifying recurrence in post-treatment gliomas and to qualitatively assess spatial concordance between the three modalities using simultaneous PET-MR acquisition.MethodsA retrospective review of 48 cases of post-treatment gliomas who underwent simultaneous PET-MRI using C11 methionine as radiotracer was performed. MR perfusion and diffusion sequences were acquired during the PET study. The following parameters were obtained: TBRmax, TBRmean, SUVmax, and SUVmean from the PET images; rCBV from perfusion; and ADCmean and ADCratio from the diffusion images. The final diagnosis was based on clinical/imaging follow-up and histopathology when available. ROC curve analysis in combination with logistic regression analysis was used to compare the diagnostic performance. Spatial concordance between modalities was graded as 0, 1, and 2 representing discordance, < 50% and > 50% concordance respectively.ResultsThere were 35 cases of recurrence and 13 cases of post-treatment changes without recurrence. The highest area under curve (AUC) was obtained for TBRmax followed by rCBV and ADCratio. The AUC increased significantly with a combination of rCBV and TBRmax. Amino acid PET showed the highest diagnostic accuracy and maximum agreement with the final diagnosis. There was discordance between ADC and PET in 22.9%, between rCBV and PET in 16.7% and between PET and contrast enhancement in 14.6% cases.ConclusionAmino acid PET had the highest diagnostic accuracy in identifying recurrence in post-treatment gliomas. Combination of PET with MRI further increased the AUC thus improving the diagnostic performance.
Highlights
Gliomas are the most common primary brain neoplasms (Ostrom et al, 2018)
We compared the diagnostic accuracies of amino acid PET, MR perfusion, and diffusion as standalone modalities and in combination in identifying recurrence in treated gliomas using simultaneous PET-MR acquisition
Demographics, primary lesion characteristics, and final diagnosis There were 48 cases of post-treatment glial brain tumors who underwent simultaneous PET-MR imaging during the study period
Summary
Gliomas are the most common primary brain neoplasms (Ostrom et al, 2018). Maximal safe surgical excision with adjuvant chemoradiotherapy is the mainstay of treatment for high grade gliomas (grade III and IV). Recurrence rates continue to remain high with poor overall survival despite treatment especially in case of glioblastoma (Weathers & Gilbert, 2015; Stupp et al, 2005a). This mandates stringent post-treatment clinical and imaging surveillance. Increased uptake by inflammatory cells and high background uptake by the normal brain parenchyma can lead to a false diagnosis (Nihashi et al, 2013). In this regard, PET imaging with alternate metabolites like C-11 methionine may be advantageous in view of reduced normal parenchymal uptake. A qualitative assessment of spatial concordance between increased metabolic uptake on PET, elevated perfusion on dynamic susceptibility contrast (DSC) MRI, and restricted diffusion on diffusion-weighted imaging was performed
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