First online real-time motion-including prostate and bladder dose reconstruction during prostate radiotherapy

Area of Science:

• Medical Physics
• Radiation Oncology
• Image-Guided Therapy

Background:

• Prostate radiotherapy doses can be distorted by organ motion.
• Real-time calculation of motion-induced dose distortions during treatment is a significant challenge.

Purpose of the Study:

• To present the first real-time, motion-including dose reconstruction during prostate radiotherapy.
• To validate the accuracy and speed of the developed in-house software for online dose calculation.
• To assess the effectiveness of intrafractional image guidance in mitigating dose distortions.

Main Methods:

• Twenty patients underwent stereotactic prostate radiotherapy with intrafractional image guidance.
• In-house software performed real-time dose reconstruction, accounting for organ motion.
• Reconstructed doses were validated against a clinical treatment planning system (TPS).
• Hypothetical doses without repositioning were reconstructed to demonstrate the benefit of motion mitigation.

Main Results:

• Real-time dose calculations showed high agreement with TPS (e.g., 0.1% difference for CTV D95%).
• Online dose reconstruction averaged 336 ms, proving real-time applicability.
• Intrafractional image guidance minimized average dose distortions to 0.0% for CTV and +0.1% for bladder.
• Without repositioning, dose deviations could reach clinically unacceptable levels (up to -42.5% for CTV D95%).

Conclusions:

• This study achieved the first clinical real-time motion-including dose reconstruction for target and organs at risk.
• The developed method paves the way for real-time dose-guided radiotherapy.
• Accurate online dose reconstruction enhances treatment precision and patient safety.