MRI Tumor-Tracked Cancer Treatment

Gino Fallone and colleagues
Cross Cancer Institute
Edmonton, AB, Canada

Radiation therapy targeting in cancer treatment involves many uncertainties, including the movement of targeted sites due to breathing and the like. Magnetic resonance imaging (MRI) can accurately identify the location of a tumor in soft tissue, but unfortunately its magnetic field can interfere with radiation treatment delivered by a linear particle accelerator (Linac). A team of researchers at the Cross Cancer Institute (CCI) in Canada set out to create a simulation that would make it possible for MRI to be used simultaneously with Linac radiation treatment so that patients can receive the care they need in a much more efficient fashion. On the other hand, the electromagnetic field from MRI can influence the path of electrons produced by Linac.

A magnetostatic simulation was needed to establish a means of shielding the Linac radiation treatment from the MRI’s magnetic fields. The shield that the CCI designed is more than three times lighter than the original, and it dramatically reduces the MRI’s field inhomogeneity by more than three times. It meant they could combine MRI and Linac in order to form an ideal treatment system that could pinpoint any tumor at all times during treatment.

COMSOL Multiphysics was also used to design a 30-cm-long Linac system generating a 10 MeV electron beam--this means that significantly less room is needed to house the Linac-MR treatment system. The optimal combination of MRI and Linac, and the room in which the new installation would be housed was evaluated with COMSOL Multiphysics. Simulation played a vital role in the progression towards clinical use of such a combination. The simulations verified that designing the Linac MR scanner to move together as one whole system provided the best results.