Surrogate gating strategies for the Elekta Unity MR-Linac gating system

Area of Science:

• Medical Physics
• Radiotherapy Technology
• Image-Guided Therapy

Background:

• MRI-guided adaptive radiotherapy offers real-time target monitoring without extra imaging dose.
• Elekta's comprehensive motion management (CMM) enables automatic beam gating on the Unity MR-Linac.
• Accurate tracking and gating depend on clear target visualization, which can be challenging for certain sites.

Purpose of the Study:

• To develop robust tracking surrogate strategies for challenging treatment sites.
• To expand the applicability of CMM for MRI-guided adaptive radiotherapy.
• To overcome limitations in visualizing primary targets for accurate gating.

Main Methods:

• Developed site-specific surrogate tracking strategies for lung, pancreas, liver, and prostate cancer patients.
• Utilized the Unity MR-Linac with CMM for adaptive radiotherapy.
• Created surrogate volumes to enhance imaging detail and drive gating decisions.

Main Results:

• Successfully generated robust, site-specific surrogate structures for tracking.
• Thoracic surrogates expanded into the lung, avoiding the heart and great vessels.
• Pancreatic surrogates incorporated the inferior liver edge; liver and prostate surrogates involved uniform expansion, avoiding nearby ribs.

Conclusions:

• Developed strategies enable gating of complex moving targets across various treatment sites.
• These surrogate approaches enhance the precision of MRI-guided radiotherapy.
• Facilitated wider clinical application of comprehensive motion management in adaptive radiotherapy.