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In-beam proton range monitoring during proton therapy: a Monte Carlo study on the feasibility of secondary gamma imaging
KTH, School of Engineering Sciences (SCI).
2016 (English)Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

Proton radiation therapy allows for delivering a high dose to a well-confinedregion of interest due to the characteristic proton dose deposition. Due to protonrange straggling, anatomic variations in patients and small patient setup errors,treatment plans needs to account for proton range uncertainties of up to 3.5% invivo.Therefore, it is highly desirable to measure the proton range on-line in orderto minimize margins in the treatment plan. Initially, the feasibility of on-linerange monitoring through prompt gamma imaging and Positron EmissionTomography (PET) at different proton energies is evaluated using GEANT4Application for Tomographic Emission (GATE) Monte Carlo (MC) simulations.In the second phase, the performance of a lead knife-edge slit system for promptgamma imaging was evaluated with MC simulations. Results from simulationsindicate that prompt gamma emission and PET isotope production is correlatedwith proton range, with discrete prompt gamma emission lines from Carbon (4.4MeV) showing good correlation. The evaluated system was able to image thepeak gamma emission location at three different slit positions with promisingprecision ± 1 mm, ± 0.7 mm and ± 1.3 mm, and average shifts of -2 mm, -3 mmand -4 mm, respectively. The proton range was resolved with mean profile shiftsof -12 ± 1 mm, -13 ± 0.7 mm and -14 ± 1.3 mm, following prompt gamma crosssectionbehavior with peak emission- and threshold energies. The results providean indication of the potential of the knife-edge slit system and future work willinclude more extensive MC simulations and experimental measurements at the Skandion clinic to determine its clinical validity.

Abstract [sv]

Strålbehandling av cancer med hjälp av protoner är fördelaktigt jämfört medkonventionell strålterapi då protonerna kan leverera en hög dos till ett välavgränsat område samtidigt som dosen till intilliggande vävnad effektivtreduceras. Tack vare statistiska variationer i protoners dosfördelning, anatomiskaavvikelser i patienter samt små fel vid patientfixering måste behandlingsplanerinnehålla marginaler som motsvarar ca 3.5% avvikelse i protonräckvidd. Att irealtid kunna mäta protoners räckvidd i patienten skulle vara tills stor nytta ochskulle bidra till att minska marginalerna i behandlingsplanen. I ett första skede avarbetet undersöktes möjligheten att avbilda protonräckvidden med promptgammaemission och Positron Emissions Tomografi (PET) genom GEANT4Application for Tomographic Emission (GATE) Monte Carlo (MC) simuleringar.Resultatet från MC simuleringarna användes sedan för att utvärdera ettdetektorsystem för prompt-gamma avbildning. Simuleringarna indikerade attproduktion av både prompt-gamma och PET isotoper är korrelerade medprotonernas räckvidd, särskilt 4.4 MeV emissionslinjen från Kol. Positionen förmaximal gamma emission kunde avbildas för tre olika positioner idetektorsystemet med en medelförskjutning på -2 ± 1 mm, -3 ± 0.7 mm och -4 ±1.3 mm. Detektorprofilen var förskjuten -12 ± 1 mm, -13 ± 0.7 mm och -14 ± 1.3mm jämfört med protonräckvidden p.g.a. interaktionernas energiberoende.Resultatet påvisar detektorsystemets potential att avbilda prompt-gamma fotoneroch framtida arbete omfattar ytterligare MC simuleringar och experimentellamätningar på Skandionklinken.

Place, publisher, year, edition, pages
TRITA-FYS, ISSN 0280-316X ; 2016:44
National Category
Physical Sciences
URN: urn:nbn:se:kth:diva-188651OAI: diva2:937846
Available from: 2016-08-23 Created: 2016-06-16 Last updated: 2016-08-23Bibliographically approved

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