Direct tumor visual feedback during free breathing in 0.35T MRgRT

Area of Science:

• Radiation Oncology
• Medical Imaging
• Image-Guided Therapy

Background:

• Tumor motion during free breathing poses challenges in radiotherapy, potentially affecting treatment accuracy.
• Magnetic resonance-guided radiotherapy (MRgRT) offers real-time imaging for precise tumor targeting.
• Patient self-monitoring of tumor motion can be a valuable adjunct to existing radiotherapy techniques.

Purpose of the Study:

• To develop and evaluate a system providing direct tumor visual feedback to patients during free-breathing MRgRT.
• To assess the system's feasibility in reducing tumor motion range and beam-on time.
• To explore the potential benefits of patient-guided tumor motion control in MRgRT.

Main Methods:

• A novel system was developed to project real-time cine MR images with target and auto-segmented contours onto an MR-compatible display for patient viewing.
• A six-patient clinical evaluation was conducted, comparing tumor motion range and beam-on time with and without visual feedback.
• Probability analysis of tumor position relative to gating contours and beam-on time measurements were used to evaluate system efficacy.

Main Results:

• The target contour extended outside the gating contour for 33.6% of the time without visual guidance and 37.2% with visual guidance.
• Average maximum motion outside the gating contour was 14.4 mm without and 13.0 mm with visual guidance, showing no significant difference.
• Beam-on time percentages were 43.9% without and 48.0% with visual guidance, also not statistically significant (P=0.34).

Conclusions:

• The direct tumor visual feedback system is clinically feasible and adaptable for MRgRT workflows.
• The system empowers patients to visualize and actively attempt to minimize their tumor motion during free breathing.
• Further investigation is warranted to optimize patient-guided motion control strategies in MRgRT.