Real-time tumor tracking with preprogrammed dynamic multileaf-collimator motion and adaptive dose-rate regulation

Area of Science:

• Medical Physics
• Radiation Oncology
• Image-Guided Therapy

Background:

• Real-time tumor tracking is crucial for accurate radiotherapy during free breathing.
• Existing multileaf-collimator (MLC) based tracking methods face challenges with real-time motion control and clinical implementation.

Purpose of the Study:

• To develop and evaluate a novel method for real-time tumor tracking using dynamic MLC motion and real-time dose-rate control.
• To simplify the technical requirements for MLC-based tumor tracking in clinical settings.

Main Methods:

• The proposed dose-rate-regulated tracking (DRRT) method utilizes a preprogrammed dynamic MLC sequence synchronized with real-time dose-rate modulation.
• Tumor motion is implicitly accounted for in the MLC sequence, while breathing irregularities are managed by adjusting the radiation dose rate.
• The method leverages existing linear accelerators with dynamic MLC capabilities and external beam dose rate control.

Main Results:

• Tracking error was less than 1 mm (1 sigma) for 13 out of 14 patients, neglecting treatment machine response time.
• Film measurements on a moving phantom demonstrated superior accuracy with DRRT (97% points < 1 gamma, 3%/2mm criteria) compared to non-DRRT delivery (87%).
• DRRT proved effective in real-time tracking despite irregular patient breathing frequencies, amplitudes, and baseline drifts.

Conclusions:

• Dose-rate-regulated tracking (DRRT) offers a feasible solution for real-time tumor tracking in radiotherapy.
• The DRRT method simplifies real-time control, enabling the use of existing linac technology for improved treatment accuracy.
• Further research is needed to establish patient selection criteria for clinical application of DRRT.