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Development of an MR-only radiation therapy planning workflow

Patients who have cancer often have to undergo difficult treatments in an attempt to rid their body of the disease. Whether this is done using chemotherapy (medication) or radiation therapy, the process can be difficult. However, the team at Skåne University Hospital in Lund, Sweden, has begun to develop a workflow for radiation therapy planning using magnetic resonance (MR) only techniques.

Skåne University Hospital's goal is to improve accuracy of their radiation treatments, as well as enable any necessary increases in radiation dose to cancer specific areas with more precision.1 Furthermore, the team would like to avoid the introduction of image registration errors which may occur using both MR and computed tomography (CT) imaging.

MRI for radiation therapy1

Lars E. Olsson, who is a Professor of Medical Radiation Physics and physicist, and Adalsteinn Gunnlaugsson, a physician and Senior Consultant in the Department of Oncology at the hospital, began their pursuit of an MR-only planning technique for radiation therapy of prostate cancer patients in 2015. The two see potential in MR, because they observe better soft tissue contrast and resolution using MR instead of CT. The details that are revealed by these advantages of MR may also help visualize the details of the tissue being irradiated, allowing for an increased dose to the tumor while sparing normal tissue.

Traditionally, when MR is used to plan and direct cancer therapy, CT is needed for dose calculations. In order to accurately calculate the dosage, MR and CT images need to be aligned, because they are use different systems at different times. If they are not aligned accurately, it could lead to a higher radiation dose to healthy tissue.

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MR processes created by researchers1

The team at Skåne University Hospital is working with another company to find ways to avoid CT scanning when using MR for radiation therapy planning and dosage. They now derive Housfield Units (HU) maps using synthetic CT images which are synthesized from MR data. A Statistical Decomposition Algorithm generates the images by using tissue classifications. The team found the generated images to be accurate in comparison to conventional CT data.2

Since the creation of Skåne University Hospital's MR-only workflow, their work has been validated through numerous research studies.1 The team themselves have conducted research using their MR-only workflow, and other institutions have begun to use the workflow as well. As a result, teams have begun to adapt the workflow to different patient types. In 2018, the team also began to investigate using the workflow to image the brain for planning and radiation therapy. This additional workflow is still in the research stages, but the team is eager to continue investigating the process.

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References:

  1. Development of an MR-only radiation therapy workflow. SIGNA Pulse of MR. http://www.gesignapulse.com/signapulse/spring_2019/MobilePagedArticle.action?articleId=1488810&app=false#articleId1488810. Last accessed September 6, 2019.
  2. Siversson C, Nordstrom F, Nilsson T, et al. Technical Note: MRI only prostate radiotherapy planning using the statistical decomposition algorithm. Med Phys. 2015 Oct;42(10):6090-7.