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Building An Anatomical Filter to Facilitate 3D Whole Brain Spectroscopic MRI Into Glioblastoma (GBM) Treatment Planning

E Schreibmann

E Schreibmann*, S Gurbani , H Shim , Emory Univ, Atlanta, GA


TU-H-605-4 (Tuesday, August 1, 2017) 4:30 PM - 6:00 PM Room: 605

Purpose: High resolution 3D whole brain spectroscopic MRI (sMRI) is proposed to guide radiation dose escalation for glioblastoma patients in a three site clinical trial (Emory University, Johns Hopkins University, and University of Miami) starting summer 2017. Specifically, choline-to-N-acetyl aspartate (Cho/NAA) will be used to define the target volume. To facilitate the safe use of Cho/NAA-guided radiation dose escalation, we are building an anatomical filter to eliminate regions with critical structures and areas known to have high baseline Cho/NAA.

Methods: Our published results demonstrated that Cho/NAA ratio map identifies tumor infiltration beyond standard MR imaging (contrast-enhanced T1w and T2w/FLAIR) by histology-image correlation study (Cordova et al. 2016). In addition, sMRI metabolic abnormalities before radiation therapy predicts the regions at high-risk for recurrence and exhibit an inverse relationship with progression-free survival. For clinical application, the target volume encompass 2-fold elevations in Cho/NAA compared to contralateral normal-appearing white matter is overlaid on the high-resolution T1w-MPRAGE (magnetization-prepared rapid gradient echo) images are rigidly co-registered with clinical images. A multi-atlas approach provides the best trade-off between speed and accuracy. To speed up the atlas selection, we quantify the anatomy within the atlases through their principal components with the each atlas similarity scored by a Mahalanobis distance of the subject-atlas eigenvectors.

Results: Labeling accuracy was measured between automated and manual segmentations using the Dice coefficient Exclusion zones were labeled with an accuracy of 0.96 for the cerebellum and 0.83 for the ventricles. Similarly, radiotherapy critical structures were scored at 0.68 for the lens, 0.89 for the eyes, 0.91 for the optical nerves, and 0.74 for the brainstem.

Conclusion: We have developed an automated anatomical filters that facilitate safe use of sMRI data for radiation dose escalation study.

Funding Support, Disclosures, and Conflict of Interest: This work was supported by a grant from Varian Medical Systems

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