MRI is the clinically preferred method of imaging soft tissue. MRI technology can give clinicians a clearer view of the patient’s internal organs, such as the lung, without delivering the extra ionizing radiation of CT imaging (below).
Until now, radiation oncologists have not been equipped with the full set of tools they need to track and adapt to the movement of a patient’s internal anatomy during treatments. With other radiation therapy technologies, imaging can only take place before or after the treatment. At the moment of treatment, while the beam is on, clinicians cannot see exactly where the therapy target is located inside a patient’s body. Treatment plans can be very precise, but they're based on images captured minutes, days, even weeks before the treatment. Study after study has shown that soft-tissue motion can shift the positions of the tumor and nearby organs, creating the possibility that the beam will miss the tumor's edges or unnecessarily irradiate healthy tissue.
Other RT vendors have tried to come up with ways to improve the targeting of a radiation beam by approximating the tumor location with external markers or implanted fiducials—methods that may be invasive or may expose the patient to additional ionizing radiation from imaging devices. Even with these methods, it still isn’t possible to see what’s going on inside the patient during the treatment.
ViewRay’s MRI guided RT system is designed to solve this problem. Using a unique combination of MR imaging and radiation therapy delivery technologies, the MRIdian and MRIdian Linac systems provide continuous soft-tissue imaging while the treatment beam is on—along with the tools to refine the target and re-optimize the dose while the patient is on the treatment table.