Implementing Visual Guidance In 0.35T MRI-Guided Stereotactic Body Radiotherapy (SBRT): From MRI Simulation to Radiotherapy
Abstract
Purpose
Onboard real-time MRI imaging in MR-guided radiotherapy (MRgRT) offers exceptional benefits for treating abdominothoracic cancers. However, gated delivery can be prolonged due to irregular patient breathing, which may diminish these advantages. We addressed this issue by implementing visual guidance in 0.35T MRgRT, spanning from MRI simulation to radiotherapy.
Methods
Visual guidance was implemented in two distinct phases. First, during daily MRI acquisition, patients’ respiratory patterns were monitored and displayed to ensure consistent breathing. Second, during treatment delivery, the real-time movement of the target, which is coupled with respiration, was shown to the patient to help them control their breathing motion.
Results
To facilitate this, an MR-compatible LCD monitor was installed in the treatment room by a vendor, and patients were provided with mirrored glasses to view real-time visual feedback. While the vendor’s software displayed the target and gating boundaries during MRgRT delivery, no integrated solution existed for the initial MRI acquisition phase. To bridge this technical gap, we developed an in-house respiratory monitoring system using an air pressure sensor to measure and display patient breathing patterns during imaging. Our workflow was specifically designed to leverage the vendor-installed display line, enabling the in-house system's video signal to be transmitted directly to the MR-compatible monitor. By implementing a dual-source switching mechanism, we established a seamless workflow that provides selective and continuous visual guidance throughout both the imaging and treatment phases. This integrated approach ensures consistent patient cooperation and maximizes motion control across the entire clinical procedure.
Conclusion
We successfully established a comprehensive visual guidance workflow for 0.35T MRgRT by integrating a vendor-provided system with an in-house developed solution. This seamless, dual-source approach enables consistent respiratory control from imaging to treatment, enhancing the effectiveness of the MRgRT.