Non-coplanar trajectories to improve organ at risk sparing in volumetric modulated arc therapy for primary brain tumours

Smyth, G, Evans, Philip, Bamber, JC, Mandeville, HC, Welsh, LC, Saran, FH and Bedford, JL (2016) Non-coplanar trajectories to improve organ at risk sparing in volumetric modulated arc therapy for primary brain tumours Radiotherapy and Oncology, 121 (1). pp. 124-131.

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Abstract

Background and purpose: To evaluate non-coplanar volumetric modulated arc radiotherapy (VMAT) trajectories for organ at risk (OAR) sparing in primary brain tumour radiotherapy. Materials and methods: Fifteen patients were planned using coplanar VMAT and compared against non-coplanar VMAT plans for three trajectory optimization techniques. A geometric heuristic technique (GH) combined beam scoring and Dijkstra's algorithm to minimize the importance-weighted sum of OAR volumes irradiated. Fluence optimization was used to perform a local search around coplanar and GH trajectories, producing fluence-based local search (FBLS) and FBLS+GH trajectories respectively. Results: GH, FBLS, and FBLS+GH trajectories reduced doses to the contralateral globe, optic nerve, hippocampus, temporal lobe, and cochlea. However, FBLS increased dose to the ipsilateral lens, optic nerve and globe. Compared to GH, FBLS+GH increased dose to the ipsilateral temporal lobe and hippocampus, contralateral optics, and the brainstem and body. GH and FBLS+GH trajectories reduced bilateral hippocampi normal tissue complication probability (p = 0.028 and p = 0.043, respectively). All techniques reduced PTV conformity; GH and FBLS+GH trajectories reduced homogeneity but less so for FBLS+GH. Conclusions: The geometric heuristic technique best spared OARs and reduced normal tissue complication probability, however incorporating fluence information into non-coplanar trajectory optimization maintained PTV homogeneity.

Item Type:	Article
Subjects :	Electronic Engineering
Divisions :	Faculty of Engineering and Physical Sciences > Electronic Engineering
Authors :	Name Email ORCID Smyth, G Evans, Philip p.evans@surrey.ac.uk Bamber, JC Mandeville, HC Welsh, LC Saran, FH Bedford, JL
Date :	29 July 2016
DOI :	10.1016/j.radonc.2016.07.014
Copyright Disclaimer :	© 2016. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/
Related URLs :	Publisher
Depositing User :	Symplectic Elements
Date Deposited :	26 Jul 2016 18:01
Last Modified :	16 Jan 2019 17:06
URI:	http://epubs.surrey.ac.uk/id/eprint/811464

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