CV Science

Jérémi Vũ Bezin PhD in medical physics

Course and current status

2015-now : Postdoctoral researcher (Gustave Roussy)

2012-2015 : PhD in medical physics and imaging (Université Paris-Sud)

2011 : Master in medical physics (Université Paris-Sud)

Scientific summary

Post-doc :

Assessment of uncertainties and quality assurance in dose reconstructions for radiotherapy late effects research (www.peridosequality.fr)

Keywords : Uncertainties, dose estimates, dose–response relationship, radiotherapy late effects.

PhD :

Title : Optimization and validation of out-of-field dose calculation methods in external beam radiation therapy for use in epidemiological and clinical studies

Keywords : Radiotherapy, out-of-field dose, head scatter, leakage, multi-source modelling, thermoluminescent dosimeters

Abstract : The number of cancer survivors in developed coun-ties increases rapidly. Fifty percent of patients treated for cancer will receive radiation therapy as part of their treatment. Ionizing radiation may induce severe long term effects, including second-ary cancers and cardio-vascular diseases. Long term effects are not only due to high doses deliv-ered in target volumes, but also to lower doses, ranging from several milligrays to several grays, undesired, but inevitably delivered in the rest of the patient’s body outside the treatment beams.
Improvements in treatment planning technics and the use of computers in medicine made it possible to systematically estimate, prior to treatment, the highest doses delivered to the patient’s body. How-ever, lower doses delivered outside the treatment beams are neither taken into account nor evaluated by present treatment planning systems.
The aim of our work was to establish methods to estimate radiation doses outside photon beams from accelerators used in external radiation thera-py.
A graphics library was used to render a partial 3D representation of the accelerator and the photon sources associated. The intensity of these sources was determined using measurements performed in simple geometry fields. The calibrated model was hence used to estimate the source intensity varia-tion with respect to field size.
Using this method, we were able to estimate the variations of the TLD measured doses with respect to distance and field size with a 10% average dis-crepancy between calculations and measurements for points outside the field. Also, when testing the model in a clinical setup, the average discrepancy increased to 25%.