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

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Date
2016-10Author
Smyth, G
Evans, PM
Bamber, JC
Mandeville, HC
Welsh, LC
Saran, FH
Bedford, JL
Type
Journal Article
Metadata
Show full item recordAbstract
Background and purpose To evaluate non-coplanar volumetric modulated arc radiotherapy (VMAT) trajectories for organ at risk (OAR) sparing in primary brain tumor 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.
Collections
Subject
Humans
Brain Neoplasms
Radiotherapy Dosage
Radiotherapy Planning, Computer-Assisted
Probability
Algorithms
Models, Biological
Radiotherapy, Intensity-Modulated
Organs at Risk
Research team
Paediatric and Adolescent Radiotherapy
Radiotherapy treatment planning
Ultrasound & Optical Imaging
Language
eng
Date accepted
2016-07-19
License start date
2016-10
Citation
Radiotherapy and oncology : journal of the European Society for Therapeutic Radiology and Oncology, 2016, 121 (1), pp. 124 - 131