Findings of the AAPM Ad Hoc committee on magnetic resonance imaging in radiation therapy: Unmet needs, opportunities, and recommendations.

The past decade has seen the increasing integration of magnetic resonance (MR) imaging into radiation therapy (RT). This growth can be contributed to multiple factors, including hardware and software advances that have allowed the acquisition of high-resolution volumetric data of RT patients in their treatment position (also known as MR simulation) and the development of methods to image and quantify tissue function and response to therapy. More recently, the advent of MR-guided radiation therapy (MRgRT) - achieved through the integration of MR imaging systems and linear accelerators - has further accelerated this trend. As MR imaging in RT techniques and technologies, such as MRgRT, gain regulatory approval worldwide, these systems will begin to propagate beyond tertiary care academic medical centers and into more community-based health systems and hospitals, creating new opportunities to provide advanced treatment options to a broader patient population. Accompanying these opportunities are unique challenges related to their adaptation, adoption, and use including modification of hardware and software to meet the unique and distinct demands of MR imaging in RT, the need for standardization of imaging techniques and protocols, education of the broader RT community (particularly in regards to MR safety) as well as the need to continue and support research, and development in this space. In response to this, an ad hoc committee of the American Association of Physicists in Medicine (AAPM) was formed to identify the unmet needs, roadblocks, and opportunities within this space. The purpose of this document is to report on the major findings and recommendations identified. Importantly, the provided recommendations represent the consensus opinions of the committee's membership, which were submitted in the committee's report to the AAPM Board of Directors. In addition, AAPM ad hoc committee reports differ from AAPM task group reports in that ad hoc committee reports are neither reviewed nor ultimately approved by the committee's parent groups, including at the council and executive committee level. Thus, the recommendations given in this summary should not be construed as being endorsed by or official recommendations from the AAPM.

Intraoperative radiation therapy.

Radiation therapy has been used to treat cancers for over one hundred years. Over the last century our understanding of the biology of radiation exposure as well as our ability to safely deliver extraordinarily high doses of radiation to specific targets has led to its routine use in both curative and palliative settings for most solid tumors. External radiation beam techniques invariably involve irradiating normal tissues that are located between the radiation source and the intended target. High-energy linear accelerators have greatly reduced skin and subcutaneous radiation-induced injury; however, radiation tolerances of organs adjacent to the target do frequently limit the total amount of radiation that can be used. Intraoperative radiation therapy (IORT) can be delivered in a number of ways, with the ultimate intent of minimizing normal tissue exposure to potentially harmful doses of radiation. Multiple IORT delivery modalities are now available, all of which present potential advantages and disadvantages over other methods of treatment. The specific techniques, radiobiologic considerations, and clinical uses of IORT will be described.