Dosimetric effects of breathing motion in radiotherapy

Research output: ThesisDoctoral Thesis (compilation)

Abstract

The goal of radiotherapy is to deliver a homogeneous high dose of radiation to a tumour while minimising the dose to the surrounding healthy tissue. To achieve this, increasingly advanced treatment techniques, such as volumetric modulated arc therapy (VMAT) and proton therapy, have been developed. However, these treatment techniques are sensitive to patient motion, such as breathing, which may degrade the dose distribution to the tumour and healthy tissue. The simultaneous movement of the tumour and treatment delivery may cause unwanted heterogeneities in the dose distribution, so-called interplay effects. Treatment during deep inspiration (DI) could mitigate the motion and lead to favourable anatomical changes in the tumour position with respect to healthy tissue. The aim of the work presented in this thesis was to investigate various effects of breathing motion on the tumour and healthy tissue dose distribution in radiotherapy.

Potential healthy tissue dose sparing using DI photon or proton therapy was investigated for left-sided breast cancer and mediastinal Hodgkin’s lymphoma (HL) by performing comparative treatment planning studies. The use of DI reduced the dose to healthy tissue for left-sided breast cancer patients. It also reduced the healthy tissue dose for most mediastinal HL patients, but the benefits were more patient specific due to large variations in the disease distribution. Protons reduced the dose to healthy tissue for both left-sided breast cancer and mediastinal HL patients compared to photons, regardless of the use of DI.

A tool to simulate breathing-motion-induced interplay effects for VMAT was developed and used to investigate how interplay effects vary for different treatment scenarios. The tool was further adapted for use in a more clinical setting to investigate interplay effects for stereotactic VMAT treatment of liver metastases. Interplay effects were shown to negatively affect the dose distribution, resulting in underdosing part of the tumour. The extent of interplay effects depended on the tumour motion and treatment plan characteristics.

In conclusion, major dosimetric effects of breathing motion on radiotherapy treatment were demonstrated by the work presented in this thesis. A beneficial effect of reduced healthy tissue dose was observed when the patient used controlled DI. Furthermore, by knowing the breathing-induced motion of the tumour, the treatment delivery parameters can be selected wisely to minimise unwanted interplay effects. Knowledge of the dosimetric effects of breathing motion is important to be able to individually optimise the radiotherapy treatment.

Details

Authors
Organisations
Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Cancer and Oncology
  • Other Physics Topics

Keywords

  • radiotherapy, breathing motion, DIBH, interplay effects, VMAT, proton therapy, breast cancer, Hodgkin’s lymphoma, liver, dosimetry, treatment planning, medical physics
Original languageEnglish
QualificationDoctor
Awarding Institution
Supervisors/Assistant supervisor
Award date2018 Oct 5
Place of PublicationLund
Publisher
  • Lund University, Faculty of Science, Department of Medical Radiation Physics
Print ISBNs978-91-7753-804-2
Electronic ISBNs978-91-7753-805-9
Publication statusPublished - 2018 Sep
Publication categoryResearch

Bibliographic note

Defence details Date: 2018-10-05 Time: 09:00 Place: Strålbehandlingshusets föreläsningssal 3 vån, Klinikgatan 5, Lund External reviewer(s) Name: Nyholm, Tufve Title: Professor Affiliation: Umeå universitet ---

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Related research output

Anneli Edvardsson, Nordström, F., Crister Ceberg & Sofie Ceberg, 2018 Apr 19, In : Physics in Medicine and Biology. 63, 8, 085012.

Research output: Contribution to journalArticle

Flejmer, A. M., Anneli Edvardsson, Dohlmar, F., Josefsson, D., Mats Nilsson, Witt Nyström, P. & Dasu, A., 2016 May, In : Acta Oncologica. 55, 5, p. 577-583 7 p.

Research output: Contribution to journalArticle

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