19/05/2017 - 10:00
« Accelerated Clinical Prompt Gamma simulations for Proton Therapy »
M. HUISMAN Brent Fokke Bram
Salle des Conférences, Bibliothèque Universitaire des Sciences (Villeurbanne)
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The first part of this PhD program is the development, analysis and release of a variance reductionmethod for the simulation of prompt gammas (PGs) in clinical proton therapy simulations. Thevariance reduction method (named vpgTLE) is a two-stage track length estimation methoddeveloped to estimate the PG yield in voxelized volumes. As primary particles are propagatedthroughout the patient CT, the PG yields are computed at each step, resulting in a voxelized imageof PG production yield. The second stage uses this intermediate image as a source to generate andpropagate the number of PGs throughout the rest of the scene geometry, e.g. into a detectiondevice, corresponding to the number of primaries desired. For both a geometrical heterogeneousphantom and a complete patient CT treatment plan with respect to analog MC, at a convergencelevel of 2\% relative uncertainty in the 90\% yield region, a gain of around $10^3$ was achieved.The method agrees with reference analog MC simulations to within $10^{-4}$, with negligiblebias.The second part of this PhD program is the study of PG fall-off position (FOP) estimation in clinicalsimulations. The number of protons (spot weight) required for a consistent FOP estimate wasinvestigated for two PG cameras, a multi-parallel slit and a knife edge design, for a single spot of afully clinical simulation of a patient treatment. By studying recent treatment plans from variousproton clinics, we observe very few spots with weights over $10^8$. We did not manage to detectthe morphological change present, an approximately 13mm shift, between the (RP)CT with eitherPG camera, with such statistics. Only for $10^9$ primaries, with one of the cameras, the changemay be expected to be detected. A new spot-grouping method is proposed that combines bettermeasurement statistics with fall-off preservation.

Composition du Jury :

M. DENDOOVEN Peter Professur des Universités Rapporteur

M. JAN Sébastien Habilité à diriger des Recherches Rapporteur

MME RAFECAS Magdalena Professeur des Universités Examinateur

M. STERPIN Edmond Associate Professor Examinateur

M. SARRUT David Directeur de Recherche Directeur de Thèse

M. TESTA Etienne Maître de Conférences HDR Co Directeur de Thèse