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Beam angle optimization using angular dependency of range variation assessed via water equivalent path length (WEPL) calculation for head and neck proton therapy

Authors
 Jihun Kim  ;  Yang-Kyun Park  ;  Gregory Sharp  ;  Paul Busse  ;  Brian Winey 
Citation
 PHYSICA MEDICA-EUROPEAN JOURNAL OF MEDICAL PHYSICS, Vol.69 : 19-27, 2020-01 
Journal Title
PHYSICA MEDICA-EUROPEAN JOURNAL OF MEDICAL PHYSICS
ISSN
 1120-1797 
Issue Date
2020-01
MeSH
Algorithms ; Cone-Beam Computed Tomography ; Head and Neck Neoplasms / radiotherapy* ; Humans ; Proton Therapy* ; Protons ; Radiometry ; Radiotherapy Dosage ; Radiotherapy Planning, Computer-Assisted ; Reproducibility of Results ; Retrospective Studies ; Tomography, X-Ray Computed* ; Treatment Outcome ; Water / chemistry*
Keywords
Water equivalent path length ; Angular dependency ; Proton therapy ; Anatomic change ; Patient setup error ; Cone-beam CT ; Scatter correction
Abstract
Purpose: To investigate angular sensitivity of proton range variation due to anatomic change in patients and patient setup error via water equivalent path length (WEPL) calculations. Methods: Proton range was estimated by calculating WEPL to the distal edge of target volume using planning CT (pCT) and weekly scatter-corrected cone-beam CT (CBCT) images of 11 head and neck patients. Range variation was estimated as the difference between the distal WEPLs calculated on pCT and scatter-corrected CBCT (cCBCT). This WEPL analysis was performed every five degrees ipsilaterally to the target. Statistics of the distal WEPL difference were calculated over the distal area to compare between different beam angles. Physician-defined contours were used for the WEPL calculation on both pCT and cCBCT, not considering local deformation of target volume. It was also tested if a couch kick (10 degrees) can mitigate the range variation due to anatomic change and patient setup error. Results: For most of the patients considered, median, 75% quantile, and 95% quantile of the distal WEPL difference were largest for posterior oblique angles, indicating a higher chance of overdosing normal tissues at distal edge with these angles. Using a couch kick resulted in decrease in the WEPL difference for some posterior oblique angles. Conclusions: It was demonstrated that the WEPL change has angular dependency for the cohort of head and neck cancer patients. Selecting beam configuration robust to anatomic change in patient and patient setup error may improve the treatment outcome of head and neck proton therapy.
Files in This Item:
T9992020520.pdf Download
DOI
10.1016/j.ejmp.2019.11.021
Appears in Collections:
1. College of Medicine (의과대학) > Dept. of Radiation Oncology (방사선종양학교실) > 1. Journal Papers
Yonsei Authors
Kim, Jihun(김지훈) ORCID logo https://orcid.org/0000-0003-4856-6305
URI
https://ir.ymlib.yonsei.ac.kr/handle/22282913/190295
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