Medical Physics Faculty

Clinical and Research Interests

Stereotactic Radiotherapy

Highly conformal, high dose per fraction radiation treatments are convenient for the patient and provide an effective treatment option for many disease types and sites. Stereotactic treatments are delivered in one or more fractions, but typically less than five. Treatment techniques include stereotactic body radiotherapy (SBRT) for extra-cranial disease (such as lung, liver, spine etc.) and stereotactic radiosurgery (SRS) for intra-cranial. Dr. St. Aubin is the designated medical physicist for the Gamma Knife radiosurgery program at the University Hospital which will be used to deliver highly accurate and conformal treatments to benign and malignant tumors as well as certain functional disorders.

Medical linear accelerator design and simulation

Medical linear accelerators are the most common technology for the generation of therapeutic x-rays for cancer treatment. By redesigning and optimizing linear accelerator waveguide structures and electron injectors, increased x-ray output, higher particle energies, and smaller focal spots can be achieved. Most current medical linear accelerator technology lies within the s-band of microwave frequencies, but advancements in c-band and x-band technologies would allow for shorter waveguides, and smaller systems overall. Analysis of any new waveguide and electron gun design in external magnetic fields is critical for MRI-guided radiotherapy systems such as the Linac-MR at the CCI.

Finite Element dose calculations

Radiation transport is governed by the linear Boltzmann transport equation (LBTE). Accurate dose calculations require a numerical solution to the LBTE either via stochastic methods (Monte Carlo) or deterministic methods (grid based Boltzmann solvers). The Finite Element Method (FEM) has proven extremely accurate in the solution of the LBTE. The Linac-MR project creates an additional requirement for radiation dose calculations since patients are treated in the strong magnetic fields of the MRI. Therefore any Linac-MR related dose calculation must include the action of the Lorentz force on the relativistic particles set in motion. Investigations into first order and second order (Least Squares Finite Element) LBTE with external magnetic fields are being pursued.

Selected Publications

A. Keyvanloo, B. Burke, J. St. Aubin, D. Baille, K. Wachowicz, B. Warkentin, S. Steciw, B.G. Fallone,
"Minimal skin dose increase in longitudinal rotating bi-planar Linac-MR systems: examination of radiation energy and machine dose rate",
Phys. Med. Biol. 61, 3527-3539 (2016).

J. St. Aubin, A. Keyvanloo, B.G. Fallone,
"Discontinuous finite element space-angle treatment of the first order linear Boltzmann transport equation with magnetic fields: Application to MRI-guided radiotherapy",
Medical Physics, 43(1), pp. 195-204 (2016).

D. Baillie, J. St.Aubin, B.G. Fallone, S. Steciw,
"FEM design and simulation of a short, high-energy, S-band linac with Monte Carlo dose simulations",
Medical Physics, 42(4), pp. 2044-3052 (2015),
PubMed Link

J. St. Aubin, A. Keyvanloo, O. Vassiliev, B.G. Fallone,
"A deterministic solution of the first order linear Boltzmann transport equation in the presence of external magnetic fields,"
Med. Phys., 42, 780 - 793 (2015),
PubMed Link

D. Baille, J. St. Aubin, B.G. Fallone, S. Steciw,
"Feasibility of producing a short, high energy S-band linear accelerator using a klystron power source,"
Med. Phys. 40, 041713-1 - 041713-5 (2013).

D.M. Santos, J. St. Aubin, B.G. Fallone, S. Steciw,
"Magnetic shielding investigation for a 6 MV in-line linac within the parallel configuration of a linac-MR system,"
Med. Phys., 39, 788 - 797 (2012).

J. St. Aubin, S. Steciw, and B.G. Fallone,
"The design of a simulated in-line side-coupled 6 MV linear accelerator waveguide,"
Med. Phys. 37, 466 - 476 (2010).

J. St. Aubin, S. Steciw, and B. G. Fallone,
"An integrated 6 MV linear accelerator model from electron gun to dose in a water tank,"
Med. Phys., 37, 2279 - 2288 (2010).

J. Yun, J. St. Aubin, S. Rathee, and B. G. Fallone,
"Brushed permanent magnet DC MLC motor operation in an external magnetic field,"
Med. Phys., 37, 2131 - 2134 (2010).

J. St. Aubin, S. Steciw, and B. G. Fallone,
"Effect of transverse magnetic fields on a simulated in-line 6 MV linac,"
Phys. Med. Biol., 55, 4861 - 4869 (2010).

J. St. Aubin, D. Santos, S. Steciw, and B. G. Fallone,
"Effect of longitudinal magnetic fields on a simulated in-line 6 MV linac,"
Med. Phys., 37, 4916 - 4923 (2010).

J. St. Aubin, S. Steciw, and B. G. Fallone,
"Waveguide detuning caused by transverse magnetic fields on a simulated in-line 6 MV linac,"
Med. Phys., 37, 4751 - 4754 (2010).

J. St. Aubin, S. Steciw, and B. G. Fallone,
"Magnetic decoupling of the linac in a low-field bi-planar MR-linac hybrid system,"
Med. Phys., 37, 4755 - 4761 (2010).

(back to top)