August 05, 2016, WASHINGTON--(BUSINESS WIRE)--Regulatory News: Elekta (EKTA-B.ST) today announced that its high-field MR-linac was featured in 27 abstracts presented at the 58th American Association of Physicists in Medicine (AAPM) Annual Meeting & Exhibition, July 31 - August 4 in Washington, DC.

Elekta’s MR-linac fully integrates three subsystems to achieve unparalleled precision and accuracy in radiotherapy: an advanced linear accelerator, a 1.5 Tesla magnetic resonance imaging (MRI) system and online adaptive workflow software. Combined, these systems allow for simultaneous radiation therapy delivery and high-field MR tumor monitoring, enabling online treatment adaptions in response to changes in the targeted tumor position.

Three abstracts highlight the changing environment during radiotherapy treatment resulting from breathing, digestion and other physiologic activity, and demonstrate how MR-linac can be used to respond to these changes and to ensure accurate dosing of target tissue:
Abstract SU-D-207A-7: “The effects of inter-cycle respiratory motion variation on dose accumulation in single fraction MR-guided SBRT treatment of renal cell carcinoma”; Bjorn Stemkens, doctoral candidate in the Department of Radiotherapy at the University of Utrecht Medical Center. July 31, 2:05 p.m. - 3:00 p.m. This presentation evaluated three models used to characterize and adapt to the impact of respiratory motion on radiation dosing to the kidney during linac-based RT: static anatomy (STATIC), adjusting for motion based on timing of the respiratory cycle (AVG-RESP) and detection of motion using 3D images (PCA model). Results showing different dose observances among the models found the PCA model more effectively captured inter-cycle random motion. This allowed for mitigation of erroneous dosing that would have occurred with the AVG-RESP model. Such mitigation is essential for delivering the planned RT dose to the tumor while minimizing exposure of healthy tissue.

Abstract MO-E-BRC-0: “Fast online replanning techniques”; X. Allen Li, PhD, Professor and Chief of Medical Physics at the Medical College of Wisconsin. August 1, 3:25 p.m. – 3:45 p.m. This invited presentation was part of an education session titled “Online adaptive radiotherapy – Considerations for Practical Clinical Implementation.” Dr. Li focused on the importance of speed and high-quality imaging in online treatment replanning. High-field MR images, such as those provided by the MR-linac’s 1.5T imaging system, are ideal for replanning because they provide excellent soft tissue contrast and/or physiological information, which differentiates the tumor site from healthy tissue. High-field images also eliminate contouring uncertainties from low signal-to-noise ratio that occur with low-field images. Dr. Li shared examples of how online replanning was used to improve coverage and/or sparing using smaller margins in both the prostate and pancreas.

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