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Dynamic treatment with Leksell Gamma Knife Perfexion - A relaxed path sector duration optimization
KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Optimization and Systems Theory.
2015 (English)Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesisAlternative title
Planering och modellering av dynamisk gammaknivsbehandling (Swedish)
Abstract [en]

Stereotactic radiosurgery is an increasingly popular method for treating brain tumours and lesions. The Leksell Gamma Knife Perfexion by Elekta is one of the leading instruments for stereotactic radiosurgery. Today the treatment with the Gamma Knife is performed in a static step-and-shoot manner, where several "shots" of gamma rays are delivered to specific regions within the tumour in order to cover it. The treatment generally requires many such shots and thus, in combination with the positioning between shots, the treatment becomes time consuming. There is an interest in a continuous dose delivery where the dose would be delivered through a continuous path through the tumour, i.e. a dynamic treatment. The notion is that this would shorten treatment times as well as increase plan quality and dose homogeneity within the tumour. A previous model for continuous dose delivery from 2014 poses the problem as path finding combined with an optimization of the speed along the path [1]. This thesis aims to improve that model by providing a new, smoothed path as well as allowing the path to be relaxed during the optimization. The findings show that treatment times can be significantly reduced and dose homogeneity as well as plan quality increased through dynamic treatment. The relaxation of the path during the optimization further improved all dynamic models. Furthermore, several interesting properties of dynamic treatment plans have been studied and presented including dose volume histograms, isodose curves and collimator settings.

Abstract [sv]

Stereotaktisk radiokirurgi ar en allt vanligare behandling av hjärntumörer och andra hjärnskador. Leksell Gamma Knife Perfexion ar ett av de ledande instrumenten inom stereotaktisk radiokirurgi. Idag utförs behandlingar med gammakniven enligt en statisk, stegvis modell där en mängd så kallade skott av gammastrålar bestrålar olika områden i tumören för att täcka hela volymen. Generellt sett kräver behandlingar många skott, vilket, i kombination med den tid det tar att ompositionera patienten inför varje skott, gör behandlingen tidskrävande. Det finns därför ett intresse för kontinuerlig dosleverans över en bana genom tumören, en så kallad dynamisk plan. Detta skulle kunna förkorta behandlingstiden markant samt även förbättra plankvalitén och doshomogeniteten i tumören. En studie från 2014 föreslår att en dynamisk planering kan formuleras som en optimering av banan följt av en optimering av hastigheten längs banan [1]. Syftet med den här uppsatsen är att förbättra den modellen genom en förbättrad bana, vilket involverar att relaxera banans placering genom att inkludera den i hastighetsoptimeringen. Resultaten från studien visar att behandlingstiden för en tumör kan bli drastiskt minskad med dynamisk behandling samtidigt som plankvalitén och doshomogeniteten ökar. Den nya funktionen som tillåter att banan förändras under hastighetsoptimeringen ger ytterligare förbättringar till de dynamiska planerna. Slutligen så presenteras era intressanta aspekter och egenskaper hos dynamiska planer så som dos/volym-histogram, isodoskurvor och kollimatorinställningar.

Place, publisher, year, edition, pages
2015.
Series
TRITA-MAT-E, 2015:45
National Category
Computational Mathematics
Identifiers
URN: urn:nbn:se:kth:diva-170137OAI: oai:DiVA.org:kth-170137DiVA: diva2:827429
External cooperation
Elekta
Subject / course
Optimization and Systems Theory
Educational program
Master of Science - Industrial Engineering and Management
Supervisors
Examiners
Available from: 2015-06-27 Created: 2015-06-27 Last updated: 2015-06-27Bibliographically approved

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