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Bringing together the high-quality 3D images of MRI with the intense tumor-killing x-rays of a linear accelerator, scientists are building a prototype that could enable powerful x-ray beams to become a viable treatment option for several cancers. Bringing together the high-quality 3D images of MRI with the intense tumor-killing x-rays of a linear accelerator, scientists at the Alberta Cancer Board are building a prototype that could for the first time enable powerful x-ray beams to become a viable treatment option for liver, stomach and pancreatic cancers, which currently must be treated with surgery, drugs, or internal radioactive seeds in most cases. The hybrid device could also improve results for all cancer patients receiving radiation therapy.

Using a process called advanced real-time adaptive radiotherapy (ART), the prototype system will allow for near-real-time 3D magnetic resonance imaging (MRI) at the same time radiation is being administered. MRI can provide higher-quality images of tumors and organs than x-rays or computed tomography (CT) machines. In addition, it is the only imaging method that can truly provide high-quality, near-real-time 3D images inside the body.

Combining a linear accelerator used for radiation treatments and an MRI is difficult because they function on incompatible scientific and engineering principles. ART overcomes the issue by rotating an MRI machine and a linear accelerator together. The two machines are fixed with respect to each other and rotate in unison around the patient, obtaining images and delivering radiation treatment from all angles. This fixed-system concept reduces electromagnetic interference between the linear accelerator and MRI.

A finished prototype is expected by December 2007. According to the researchers, the machine will improve the accuracy of radiation treatments for solid tumors, thereby reducing side effects. In addition, it could improve treatment for lung and prostate cancers where it is still difficult to administer sufficient radiation doses to obtain a better chance of a cure.