Marie-Pierre Milette

Adjunct Professor

Medical Physics, Physics

Other Titles: Medical Physicist, BC Cancer Agency, Centre for the Southern Interior
Email: marie-pierre.milette@ubc.ca

Research Summary

Treatment planning optimization; treatment verification.

Research Interests & Projects

Volumetric Modulated Arc Therapy (VMAT) is a major advance from existing treatment delivery technique that has been implemented worldwide. The treatment plan optimization used by Varian Medical Systems was invented by a Medical Physicist in British-Columbia. Prior to the VMAT era, treatments were composed of a limited number of static modulated radiation beams. VMAT treatments are delivered by rotating the modulated radiation beam around the patient leading to improved dose conformity and normal tissue sparing while shortening treatment times threefold. The VMAT delivery is restricted to a 2 dimensional plane and by the clearance between the equipment producing the modulated radiation beam and the patient.

The new generation of Linac, manufactured by Varian Medical System and called TrueBeam Linac, are installed at the BC Cancer Agency Centre for the Southern Interior. TrueBeam’s advanced control features are designed to allow complex three dimensional trajectory beam delivery by dynamically moving multiple components simultaneously while the radiation beam is on. It is envisioned that by using the extra degrees of freedom of motion that are available in TrueBeam, it is possible to create optimal dose distributions that are not achievable by VMAT. Several clinical sites stand to benefit from reduced treatment times and decreased normal tissue toxicity using trajectory based treatment delivery. However, patients will not benefit from these advantages until a treatment plan optimization for trajectory based treatment is created.

Our research focuses on trajectory treatment plan optimization and treatment delivery verification. The current plan optimization algorithms are incapable to utilize the additional degrees of freedom and would require exponentially longer optimization time. This N dimensional problem requires new optimization techniques to fully exploit the benefit of trajectory based treatments. Before trajectory based treatments can be used clinically, new treatment delivery verification tools are necessary. We are investigating different solutions such as Monte Carlo simulations and film dosimetry.