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
significantly lower Dmax and D1% than the VMAT and NC-VMAT plans (p < 0.05), whereas the D99% and Dmin were significantly 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 significantly 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 smallest
(p < 0.05) among the 3 plans. HA planning, instead of coplanar and noncoplanar VMAT,
significantly reduces the dosage to which the contralateral hippocampus as well as
other OARs are exposed without compromising on target coverage.
Keywords
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Article info
Publication history
Published online: January 16, 2023
Accepted:
December 6,
2022
Received in revised form:
December 5,
2022
Received:
August 25,
2022
Publication stage
In Press Corrected ProofIdentification
Copyright
© 2022 American Association of Medical Dosimetrists. Published by Elsevier Inc. All rights reserved.
