Glioma consensus contouring recommendations from a MR-Linac International Consortium Research Group and evaluation of a CT-MRI and MRI-only workflow

Abstract

Introduction This study proposes contouring recommendations for radiation treatment planning target volumes and organs-at-risk (OARs) for both low grade and high grade gliomas. Methods Ten cases consisting of 5 glioblastomas and 5 grade II or III gliomas, including their respective gross tumor volume (GTV), clinical target volume (CTV), and OARs were each contoured by 6 experienced neuro-radiation oncologists from 5 international institutions. Each case was first contoured using only MRI sequences (MRI-only), and then re-contoured with the addition of a fused planning CT (CT-MRI). The level of agreement among all contours was assessed using simultaneous truth and performance level estimation (STAPLE) with the kappa statistic and Dice similarity coefficient. Results A high level of agreement was observed between the GTV and CTV contours in the MRI-only workflow with a mean kappa of 0.88 and 0.89, respectively, with no statistically significant differences compared to the CT-MRI workflow (p = 0.88 and p = 0.82 for GTV and CTV, respectively). Agreement in cochlea contours improved from a mean kappa of 0.39 to 0.41, to 0.69 to 0.71 with the addition of CT information (p < 0.0001 for both cochleae). Substantial to near perfect level of agreement was observed in all other contoured OARs with a mean kappa range of 0.60 to 0.90 in both MRI-only and CT-MRI workflows. Conclusions Consensus contouring recommendations for low grade and high grade gliomas were established using the results from the consensus STAPLE contours, which will serve as a basis for further study and clinical trials by the MR-Linac Consortium.

Chemical exchange saturation transfer MRI in central nervous system tumours on a 1.5 T MR-Linac

“…This would be possible by incorporating into our analysis, the quantitative T1, T2, MT data acquired on separate days as part of our larger multi-parametric imaging protocol [32]. CEST parameters within the GTVs were used, but quantification in tumour ROIs that have more spatially homogeneous signals (e.g., in core, peripheral or FLAIR hyperintense regions) can be considered [28,41,51,52].…”

Quantitative Mapping of Individual Voxels in the Peritumoral Region of Glioblastoma to Distinguish Between Tumor Infiltration and Edema

“…Few studies had shown a potentially positive impact on survival in patients undergoing supratotal resection or "FLAIRectomy" [22,23]. Another potential application for the current study will be in guiding RT target volumes, speci cally targeting areas of in ltrative tumor, as the standard practice includes a wider margin in an empirical manner [24]. Identifying and excluding areas of reactive edema with a lower likelihood of microscopic disease from the target volumes can help reduce treatment toxicities and adopt individualized target volumes.…”

Clinically Delivered Treatment for Glioma Patients on a Hybrid Magnetic Resonance Imaging (MRI)-Linear Accelerator (MR-Linac) and a Cone Beam CT (CBCT)-Guided Linac: Dosimetric Comparisons with In Vivo Skin Dose Correlation

“…Delineation of OARs, gross tumor volume (GTV), and clinical target volume (CTV) were de ned based on glioma consensus contouring guidelines [22]. Planning target volume (PTV) was generated as a 0.4-cm isotropic expansion of the CTV.…”