<abstract xmlns="http://www.w3.org/1999/xhtml"><sec id="j_raon-2017-0033_s_023_w2aab3b7b3b1b6b1aab1c18b1Aa"><h3>Introduction</h3><p>Deformable image registration (DIR) is used to modify structures according to anatomical changes for observing the dosimetric effect. In this study, megavoltage computed tomography (MVCT) images were used to generate cumulative doses for nasopharyngeal cancer (NPC) patients by various DIR methods. The performance of the multiple DIR methods was analysed, and the impact of dose accumulation was assessed.</p></sec><sec id="j_raon-2017-0033_s_024_w2aab3b7b3b1b6b1aab1c18b2Aa"><h3>Patients and methods</h3><p>The study consisted of five NPC patients treated with a helical tomotherapy unit. The weekly MVCT images at the 1<sup>st</sup>, 6<sup>th</sup>, 11<sup>th</sup>, 16<sup>th</sup>, 21<sup>st</sup>, 26<sup>th</sup>, and 31<sup>st</sup> fractions were used to assess the dose accumulation by the four DIR methods. The cumulative dose deviations from the initial treatment plan were analysed, and correlations of these variations with the anatomic changes and DIR methods were explored.</p></sec><sec id="j_raon-2017-0033_s_025_w2aab3b7b3b1b6b1aab1c18b3Aa"><h3>Results</h3><p>The target dose received a slightly different result from the initial plan at the end of the treatment. The organ dose differences increased as the treatment progressed to 6.8% (range: 2.2 to 10.9%), 15.2% (range: -1.7 to 36.3%), and 6.4% (range: -1.6 to 13.2%) for the right parotid, the left parotid, and the spinal cord, respectively. The mean uncertainty values to estimate the accumulated doses for all the DIR methods were 0.21 ± 0.11 Gy (target dose), 1.99 ± 0.76 Gy (right parotid), 1.19 ± 0.24 Gy (left parotid), and 0.41 ± 0.04 Gy (spinal cord).</p></sec><sec id="j_raon-2017-0033_s_026_w2aab3b7b3b1b6b1aab1c18b4Aa"><h3>Conclusions</h3><p>Accuracy of the DIR methods affects the estimation of dose accumulation on both the target dose and the organ dose. The DIR methods provide an adequate dose estimation technique for observation as a result of inter-fractional anatomic changes and are beneficial for adaptive treatment strategies.</p></sec></abstract>

IntroductionDeformable image registration (DIR) is used to modify structures according to anatomical changes for observing the dosimetric effect. In this study, megavoltage computed tomography (MVCT) images were used to generate cumulative doses for nasopharyngeal cancer (NPC) patients by various DIR methods. The performance of the multiple DIR methods was analysed, and the impact of dose accumulation was assessed.Patients and methodsThe study consisted of five NPC patients treated with a helical tomotherapy unit. The weekly MVCT images at the 1st, 6th, 11th, 16th, 21st, 26th, and 31st fractions were used to assess the dose accumulation by the four DIR methods. The cumulative dose deviations from the initial treatment plan were analysed, and correlations of these variations with the anatomic changes and DIR methods were explored.ResultsThe target dose received a slightly different result from the initial plan at the end of the treatment. The organ dose differences increased as the treatment progressed to 6.8% (range: 2.2 to 10.9%), 15.2% (range: -1.7 to 36.3%), and 6.4% (range: -1.6 to 13.2%) for the right parotid, the left parotid, and the spinal cord, respectively. The mean uncertainty values to estimate the accumulated doses for all the DIR methods were 0.21 ± 0.11 Gy (target dose), 1.99 ± 0.76 Gy (right parotid), 1.19 ± 0.24 Gy (left parotid), and 0.41 ± 0.04 Gy (spinal cord).ConclusionsAccuracy of the DIR methods affects the estimation of dose accumulation on both the target dose and the organ dose. The DIR methods provide an adequate dose estimation technique for observation as a result of inter-fractional anatomic changes and are beneficial for adaptive treatment strategies.

Evaluation of deformable image registration (DIR) methods for dose accumulation in nasopharyngeal cancer patients during radiotherapy

Department of Radiologic Technology, Faculty of Associated Medical Sciences

Department of Radiology, Faculty of Medicine

Radiology and Oncology

This article is distributed under the terms of the Creative Commons Attribution Non-Commercial License, which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

IntroductionDeformable image registration (DIR) is used to modify structures according to anatomical changes for observing the dosimetric effect. In this...

Evaluation of deformable image registration (DIR) methods for dose accumulation in nasopharyngeal cancer patients during radiotherapy

Article Category: Research Article

Published Online: Sep 15, 2017

Page range: 438 - 446

Received: Jun 03, 2017

Accepted: Jul 16, 2017

DOI: https://doi.org/10.1515/raon-2017-0033

© 2017 Wannapha Nobnop, Imjai Chitapanarux, Hudsaleark Neamin, Somsak Wanwilairat, Vicharn Lorvidhaya, Taweap Sanghangthum

This article is distributed under the terms of the Creative Commons Attribution Non-Commercial License, which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.