Special Colloquium: Advances in Dose Calculations, Image Processing and Dose Measurements in Radiation Therapy

March 4, 2009
Location: IRMACS Theatre (ASB 10900)
Presenter: Luc Beaulieu, Departement de Physique, de Genie Physique et d'Optique Universite Laval

My research program aims at improving radiation therapy cancer treatments following four major themes: 1) dose optimization, including biological information via image fusion, 2) image processing, 3) application of next generation dose calculation algorithms and 4) development of water equivalent dosimeters. Any of these themes, alone or combined, has the potential to improve the way radiation therapy is used in the clinic.  The research effort covers many applications in radiation therapy treatments, from external beam radiation therapy to permanent prostate seed implants.

In this talk, I will look at the impact of three different research projects in the field of brachytherapy, a treatment for which radioactive sources are placed inside or in close proximity to tumor volumes. The first of these is the implementation and use of Monte Carlo dose calculations and its comparison to the actual clinical standard. The wide range of photon source energies and possible geometrical configurations in brachytherapy leads to significant variations in physical processes, e.g. cross sections. These are not well taken into account by the actual clinical standard. In the second projects, the impact of using metallic objects (sources, applicators, …) will be illustrated. Most notably, artifacts in close proximity of metal objects obscure the visibility and skew the CT numbers. CT numbers are ultimately linked to density and materials for accurate dose calculation purposes. Finally, modern radiation therapy treatments use a variety of high precision delivery techniques to literally “paint” the dose to cover the tumor and spare the organs at risk. These modalities have also demonstrated the need for new dosimeters. Over the years, we have developed a new plastic scintillating fiber dosimeters that meet the requirements of high precision, high accuracy for small field dosimetry and in vivo dosimetry. An implementation for brachytherapy will be shown.

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