Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Robust optimization of radiotherapy treatment plans considering time structures of the delivery
Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Computing Science.
2018 (English)Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

Cancer is the second largest mortal disease in Sweden, and high efforts are made to develop the treatment of cancer. One of the main treatment methods is radiotherapy, which uses ionizing radiation to damage the cancerous cells. This has the chance of stopping the cell reproduction, and the goal is to reduce the tumor and stop the tumor growth.

The most common forms of radiotherapy uses external beams to irradiate the tumor. In intensity modulated radiotherapy, IMRT, the beam fluences are optimized to give a highly conformal dose, i.e. a dose distribution which is restricted to the tumor and has low dose values outside of the tumor. A conformal dose is necessary to spare healthy tissue and sensitive organs, and thus keep the side-effects of the treatment at an acceptable level. The optimized beam shapes are created using a multileaf collimator, MLC. Finding the leaf positions and dose levels is formulated as a problem in the framework of mathematical optimization.

Currently, one of the limitations in delivering conformal dose is due to patient movement during the treatment. In IMRT, the beams are delivered by consecutive segments, and the exact pairing of the segments with the patient position will have an impact on the delivered dose. This is called the interplay effect, and can cause both underdosage of the tumor and overdosage of the surrounding tissue.

There are methods of mitigating the interplay effect. For example, the beam could be restricted to a single phase of the motion by repeatedly turning it on and off. This is known as gating. However, gating and many other interplay mitigation techniques lead to prolonged treatment times, which decreases the clinical throughput, causes higher patient discomfort and gives higher uncertainties in the delivered dose. This makes it desirable to find methods which avoid prolonged treatment times, while still giving highly conformal doses. Ideally, the best method would be to have a beam which follows any target movement. This idea is known as target tracking.

In this thesis, an optimization method is suggested which includes the interplay effect in the treatment optimization. Two main treatment strategies are proposed. The method which is simplest to implement clinically is to create plans which are robust against uncertainties in the times for the patient motion. The resulting doses are found to give acceptable target covering where similar, conventional plans give a significant target underdose. To further increase the conformality of the doses, a non-robust method paired with gating technology is suggested. This method can effectively be seen as a target tracking method, and has the possibility to give highly conformal doses under acceptable treatment times.   

Place, publisher, year, edition, pages
2018. , p. 39
Series
UPTEC F, ISSN 1401-5757 ; 18042
Keywords [en]
Radiation therapy, optimization, interplay effect, lung cancer, 4DCT, RayStation
Keywords [sv]
Strålterapi, optimering, interplay, lungcancer
National Category
Cancer and Oncology Other Medical Engineering Computational Mathematics
Identifiers
URN: urn:nbn:se:uu:diva-355628OAI: oai:DiVA.org:uu-355628DiVA, id: diva2:1230064
External cooperation
RaySearch Laboratories
Educational program
Master Programme in Engineering Physics
Supervisors
Examiners
Available from: 2018-07-03 Created: 2018-07-02 Last updated: 2018-07-03Bibliographically approved

Open Access in DiVA

fulltext(3164 kB)19 downloads
File information
File name FULLTEXT01.pdfFile size 3164 kBChecksum SHA-512
f77f4981f4fa23b1d67483dc564284c88a6bc05503b2bc7f0ca3ed3a3ee1bc5b9f59642419ef47576c3e4913cd9057943fa622666c8fbfc3513a2611b97f89d1
Type fulltextMimetype application/pdf

By organisation
Division of Computing Science
Cancer and OncologyOther Medical EngineeringComputational Mathematics

Search outside of DiVA

GoogleGoogle Scholar
Total: 19 downloads
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

urn-nbn

Altmetric score

urn-nbn
Total: 91 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf