MRI-based proton treatment planning for base of skull tumors

• Type of Material: Article
• Authors: Ghazal Shafai-Erfani, Emory University; Yang Lei, Emory University; Yingzi Liu, Emory University; Yinan Wang, Emory University; Tonghe Wang, Emory University; Jim Zhong, Emory University; Tian Liu, Emory University; Mark McDonald, Emory University; Walter Curran Jr, Emory University; Jun Zhou, Emory University; Hui-Kuo Shu, Emory University; Xiaofeng Yang, Emory University
• Language: English
• Date: 2020-09-01
• Publisher: Allen Press
• Publication Version: Final Published Version
• Copyright Statement: © 2019 The Author(s).
• License: Creative Commons Attribution 4.0 International
• Final Published Version (URL): http://dx.doi.org/10.14338/IJPT-19-00062.1
• Title of Journal or Parent Work: International Journal of Particle Therapy
• Volume: 6
• Issue: 2
• Start Page: 12
• End Page: 25
• Grant/Funding Information: This research was supported, in part, by the National Cancer Institute of the National Institutes of Health, under award R01CA215718, and an Emory Winship Cancer Institute pilot grant.
• Keywords: synthetic CT; MRI; treatment planning; Oncology; Cancer cells; Skull tumors; proton therapy
• Research Categories: Health Sciences, Rehabilitation and Therapy; Biology, Cell; Health Sciences, Oncology; Health Sciences, Radiology

Abstract

Purpose: To introduce a novel, deep-learning method to generate synthetic computed tomography (SCT) scans for proton treatment planning and evaluate its efficacy. Materials and Methods: 50 Patients with base of skull tumors were divided into 2 nonoverlapping training and study cohorts. Computed tomography and magnetic resonance imaging pairs for patients in the training cohort were used for training our novel 3-dimensional generative adversarial network (cycleGAN) algorithm. Upon completion of the training phase, SCT scans for patients in the study cohort were predicted based on their magnetic resonance images only. The SCT scans obtained were compared against the corresponding original planning computed tomography scans as the ground truth, and mean absolute errors (in Hounsfield units [HU]) and normalized cross-correlations were calculated. Proton plans of 45 Gy in 25 fractions with 2 beams per plan were generated for the patients based on their planning computed tomographies and recalculated on SCT scans. Dose-volume histogram endpoints were compared. A c-index analysis along 3 cardinal planes intercepting at the isocenter was performed. Proton distal range along each beam was calculated. Results: Image quality metrics show agreement between the generated SCT scans and the ground truth with mean absolute error values ranging from 38.65 to 65.12 HU and an average of 54.55 6 6.81 HU and a normalized cross-correlation average of 0.96 6 0.01. The dosimetric evaluation showed no statistically significant differences (p. 0.05) within planning target volumes for dose-volume histogram endpoints and other metrics studied, with the exception of the dose covering 95% of the target volume, with a relative difference of 0.47%. The c-index analysis showed an average passing rate of 98% with a 10% threshold and 2% and 2-mm criteria. Proton ranges of 48 of 50 beams (96%) in this study were within clinical tolerance adopted by 4 institutions. Conclusions: This study shows our method is capable of generating SCT scans with acceptable image quality, dose distribution agreement, and proton distal range compared with the ground truth. Our results set a promising approach for magnetic resonance imaging-based proton treatment planning.