The use of multiparametric 18F-fluoro-l-3,4-dihydroxy-phenylalanine PET/MRI in post-therapy assessment of patients with gliomas

Purpose To determine the utility of 18 F-fluoro- l -3,4-dihydroxy-phenylalanine ( 18 F-DOPA) PET/MRI versus cross-sectional MRI alone in glioma response assessment and identify whether the two techniques demonstrate different tumour features. Methods 18 F-DOPA PET/MRI studies from 40 patients were analysed. Quantitative PET parameters and conventional MRI features were recorded. Tumour volume was assessed on both PET and MRI. Using dynamic susceptibility contrast perfusion-weighted imaging, maps of cerebral blood flow (CBF) and cerebral blood volume (CBV) were obtained. Within volume of tumours of tumour features and normal-appearing white matter (NAWM) drawn on MRI, standardised uptake value (SUV) max , CBF and CBV were recorded. Presence of residual active tumour was assessed by qualitative visual assessment. Receiver operating characteristic analysis was performed univariately and on parameter combination to analyse ability to determine presence/absence of disease. Reference standard for presence of viable tissue was biopsy or clinical follow-up. Results Median SUV max was 3.4 for low-grade glioma (LGG) and 3.3 for high-grade glioma (HGG). There was a significant correlation between PWI parameters and WHO grade ( P < 0.001), but no correlation with SUV max . Median 18 F-DOPA volume was 8216.88 mm 3 for HGG and 6284.94 mm 3 for LGG; MRI volume was 6316.57 mm 3 and 5931.55 mm 3 , respectively. SUV max analysis distinguished enhancing and nonenhancing components from necrosis and NAWM and demonstrated active disease in nonenhancing regions. Visually, the modalities were concordant in 37 patients. Combining the multiparametric PET/MRI approach with all available data-enhanced detection of the presence of tumour (area under the curve 0.99, P < 0.01). Conclusion MRI and 18 F-DOPA are complementary modalities for assessment of tumour burden. Matching 18 F-DOPA and MRI in assessing residual tumour volume may better delineate the radiotherapy target volume.