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Authors: Shingo Ohira, PhD∗,†,1, Toshiki Ikawa, MD, PhD∗, Naoyuki Kanayama, MD, PhD∗, Shoki Inui, MS∗, Yoshihiro Ueda, MS∗, Masayoshi Miyazaki, PhD∗, Teiji Nishio, PhD†, Masahiko Koizumi, MD, PhD†, Koji Konishi, MD, PhD∗
∗ Department of Radiation Oncology, Osaka International Cancer Institute, Osaka, Japan
† Department of Medical Physics and Engineering, Osaka University Graduate School of Medicine, Suita, Japan
Abstract:
To compare dosimetric parameters for the hippocampus, organs at risk (OARs), and targets of volumetric modulated arc therapy (VMAT), noncoplanar VMAT (NC-VMAT), and HyperArc (HA) plans in patients undergoing postoperative radiotherapy for primary brain tumors. For 20 patients, HA plans were generated to deliver 40.05 to 60 Gy for the planning target volume (PTV). In addition, doses for the hippocampus and OARs were minimized. The VMAT and NC-VMAT plans were retrospectively generated using the same optimization parameters as those in the HA plans. For the hippocampus, the equivalent dose to be administered in 2 Gy fractions (EQD2) was calculated assuming α/β = 2. Dosimetric parameters for the PTV, hippocampus, and OARs in the VMAT, NC-VMAT, and HA plans were compared. For PTV, the HA plans provided signi?cantly lower Dmax and D1% than the VMAT and NC-VMAT plans (p < 0.05), whereas the D99% and Dmin were signi?cantly higher (p < 0.05). For the contralateral hippocampus, the dosimetric parameters in the HA plans (8.1 ± 9.6, 6.5 ± 7.2, 5.6 ± 5.8, and 4.8 ± 4.7 Gy for D20%, D40%, D60% and D80%, respectively) were signi?cantly smaller (p < 0.05) than those in the VMAT and NC-VMAT plans. Except for the optic chiasm, the Dmax in the HA plans (brainstem, lens, optic nerves, and retinas) was the smallest (p < 0.05). In addition, the doses in the HA plans for the brain and skin were the small- est (p < 0.05) among the 3 plans. HA planning, instead of coplanar and noncoplanar VMAT, signi?cantly reduces the dosage to which the contralateral hippocampus as well as other OARs are exposed without compromising on target coverage.
As of January 1, 2022, ARRT requires CE Credits for Directed Journal Readings to be based on the word count for each article. So, the number of CE Credits for each DJR article will vary for ARRT. For this article, the ARRT CE Credit will be 0.75 Credit. The MDCB CE Credits will remain at 2.5 Credits.
ARRT CQR Credit Distribution
Radiation Therapy 2017:
Procedures
Prescription and Dose Calculation = 0.75 credits
Radiation Therapy 2022:
Procedures
Prescription and Dose Calculation = 0.75 credits