October 6, 2016 — Elekta announced recently that its high-field magnetic resonance linear accelerator (MR-linac) was the focus of multiple presentations at the American Society for Radiation Oncology (ASTRO) 2016 Annual Meeting, held Sept. 25 – 28 in Boston. Additional abstracts presented by members of Elekta’s MR-linac Consortium also highlighted the need for adaptation of radiation therapy to address moving tumors and nearby organs during treatment sessions. Naturally occurring physiological movements currently limit the ability to conform the treatment to the target and increase exposure of radiation to healthy tissues.
Elekta’s MR-linac will integrate an advanced linear accelerator and a 1.5 Tesla magnetic resonance imaging (MRI) system. Combined, these systems will allow for simultaneous radiation therapy delivery and high-field MR tumor monitoring.
A joint session of ASTRO and the European Society for Radiation Oncology (ESTRO) highlighted the potential for adaptive imaging in radiation therapy during a session titled “In Room Adaptive Imaging with a Focus on MRI.” Elekta’s MR-linac was featured in two presentations during this session:
- “Linac-based MR Device”; Christopher Schultz, M.D., FACR, professor in the Department of Radiation Oncology at Froedert and Medical College of Wisconsin. This presentation discussed strategies for integrating MR-linac into current RT protocols and provided an overview of the development plan that the Elekta MR-linac Consortium is undertaking in order to generate the clinical, physics and quality control data that will be essential for developing and realizing the full clinical potential of MR-linac technology.
- “MRI Linac: Physics Perspective”; Bas Raaymakers, Ph.D., professor in the Department of Radiotherapy at University Medical Center Utrecht. This presentation highlighted the potential to leverage the power of MR-linac technology to move from pre-treatment planning to online plan adaptation and, ultimately, to real-time plan adaptation. Raaymakers also discussed the need for novel quality assurance procedures for MR-linac devices, patients and workflow.
Additional key findings related to the MR-linac Consortium’s development of MR-linac presented at the conference include:
- Abdominal organ motion is complex and can occur despite motion management strategies. Abstract #3708: “Complex Abdominal Organ Motion Assessed from MRI”; Eenas Omari, Ph.D., postdoctoral fellow in the Department of Radiation Oncology at Medical College of Wisconsin;
- Substantially improves targeting and lowers radiation dose to normal breast tissue in patients undergoing pre-operative partial breast irradiation. Abstract #3695: “Dosimetric Feasibility of Pre-operative Partial Breast Irradiation in Prone Position Using MR-linac” ; Phil Prior, Ph.D., medical physicist in the Department of Radiation Oncology at Medical College of Wisconsin;
- Clinically acceptable treatment plans for patients with locally advanced non-small cell lung cancer can be created. Abstract #3150: “Dosimetric Implications for Radical Radiotherapy on the MR-linac (MRL) in Locally Advanced Non-small Cell Lung Cancer (LA NSCLC)”; Hannah Bainbridge, M.D., clinical fellow lung team, The Institute of Cancer Research, Sutton, United Kingdom, The Royal Marsden NHS Foundation Trust, Sutton, United Kingdom;
- Online adaptive replanning is feasible for prostate cancer radiation therapy. Abstract #3639: “A Hybrid Adaptive Replanning Approach for Prostate SBRT”; Ozgur Ates, Ph.D., postdoctoral fellow in the Department of Radiation Oncology at Medical College of Wisconsin; and
- An automated quality assurance (QA) tool can quickly identify contour errors from auto-segmentation and may have utility in online adaptive replanning. Abstract #3638 “Implementation of a Machine-learning Based Automatic Contour QA Tool for Online Adaptive Radiotherapy of Prostate Cancer” ; Jing Qiao Zhang, Ph.D., postdoctoral fellow in the Department of Radiation Oncology at Medical College of Wisconsin.
Several additional presentations described the potential for MR-linac and adaptive therapy to enable dose painting — the precise delivery of varying doses of radiation to specific regions within a tumor in order to account for differences in cell type, location and density from one part of the tumor to another.
Elekta’s MR-linac is a work in progress and not available for sale or distribution.
For more information: www.elekta.com