MRI-guided Radiation Therapy (MRIgRT) using integrated MRI-Linear Accelerators, or MRI-linacs, is a rapidly advancing technology implemented in radiation therapy, offering the ability to visualize soft tissue and to adapt the treatment to anatomical and physiological changes observed prior to and during radiation therapy. Acquiring detailed, high-contrast magnetic resonance (MR) images in the treatment position both before and during treatment are new information sources and workflow changes that are specific to MRI-linacs.
The rationale for this report is to give the radiation therapy community guidance on the safe and effective clinical implementation of MRIgRT and highlight emerging evidence supporting it use. Many aspects of this promising emerging technology are addressed to maximize the safety and clinical benefit to be achieved by MRIgRT. As MRIgRT involves the merging of both magnetic resonance imaging (MRI) and radiation therapy (RT), increased complexity exists that introduces new risks and requires learning new information for those who may only have experience in one of these fields.
The report narrative begins with an overall rationale and status of MRIgRT, followed by the clinical indications for patient MRIgRT treatments across different cancer sites. A summary of the MRI-linac interoperability challenges and an overview of the MRIgRT systems that have been developed to date are given. Then, the MRIgRT process steps are given chronologically: treatment planning, image guidance, treatment adaptation, and treatment delivery. Given the differences in the MRIgRT processes compared with X-ray image guidance, the staff requirements, training and safety are discussed. The final technical section reviews MRIgRT commissioning and dosimetry.
Finally, to give new users realworld examples of MRIgRT in practice, some clinical case studies for a variety of sites and treatment complexity are given.