Multiparametric simultaneous hybrid ¹⁸F-fluorodeoxyglucose positron emission tomography/magnetic resonance imaging (¹⁸F-FDG PET/MRI) incorporating intratumoral and peritumoral regions for grading of glioma

Background: Preoperative grading gliomas is essential for therapeutic clinical decision-making. Current non-invasive imaging modality for glioma grading were primarily focused on magnetic resonance imaging (MRI) or positron emission tomography (PET) of the tumor region. However, these methods overlook the peritumoral region (PTR) of tumor and cannot take full advantage of the biological information derived from hybrid-imaging. Therefore, we aimed to combine multiparameter from hybrid ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) PET/MRI of the solid component and PTR were combined for differentiating high-grade glioma (HGG) from low-grade glioma (LGG).

Methods: A total of 76 patients with pathologically confirmed glioma (41 HGG and 35 LGG) who underwent simultaneous ¹⁸F-FDG PET, arterial spin labelling (ASL), and diffusion-weighted imaging (DWI) with hybrid PET/MRI were retrospectively enrolled. The relative maximum standardized uptake value (rSUV_max), relative cerebral blood flow (rCBF), and relative minimum apparent diffusion coefficient (rADC_min) for the solid component and PTR at different distances outside tumoral border were compared. Receiver operating characteristic (ROC) curves were applied to assess the grading performance. A nomogram for HGG prediction was constructed.

Results: HGGs displayed higher rSUV_max and rCBF but lower rADC_min in the solid component and 5 mm-adjacent PTR, lower rADC_min in 10 mm-adjacent PTR, and higher rCBF in 15- and 20-mm-adjacent PTR. rSUV_max in solid component performed best [area under the curve (AUC) =0.865] as a single parameter for grading. Combination of rSUV_max in the solid component and adjacent 20 mm performed better (AUC =0.881). Integration of all 3 indicators in the solid component and adjacent 20 mm performed the best (AUC =0.928). The nomogram including rSUV_max, rCBF, and rADC_min in the solid component and 5-mm-adjacent PTR predicted HGG with a concordance index (C-index) of 0.906.

Conclusions: Multiparametric ¹⁸F-FDG PET/MRI from the solid component and PTR performed excellently in differentiating HGGs from LGGs. It can be used as a non-invasive and effective tool for preoperative grade stratification of patients with glioma, and can be considered in clinical practice.