SU-E-J-140: Initial Clinical Assessment of a Gimbaled Linac Tumor Tracking System in a Patient Simulation Study

Area of Science:

• Medical Physics
• Radiation Oncology
• Image-Guided Therapy

Background:

• Dynamic tumor tracking is crucial for accurate radiation delivery to moving targets.
• The BrainLab/MHI Vero system integrates linac-MLC with gimbals for real-time tumor motion compensation.
• kV imaging systems enable simultaneous X-ray acquisition for correlation modeling.

Purpose of the Study:

• To evaluate the workflow and quantify the performance of the BrainLab/MHI Vero dynamic tumor tracking system in simulated clinical scenarios.
• To assess the accuracy and efficiency of the Vero system for tracking moving tumors during radiotherapy.

Main Methods:

• A simulation study was performed on 5 lung-liver patients.
• Tumor motion was quantified using Visicoil gold markers.
• The workflow included patient positioning, motion acquisition, fiducial marker detection, correlation modeling, and tracking.
• Tracking error was calculated from gimbals log-files and monitoring X-rays.
• Imaging dose was measured using thermoluminescent dosimeters (TLD).

Main Results:

• The mean absolute tracking error was 1.1 mm, with a 90% percentile of 2.1 mm.
• Imaging for correlation model building resulted in 17.6 mGy skin dose.
• An additional maximal exposure of 28.8 mGy was estimated for 1 Hz X-ray monitoring during treatment.
• Average patient setup time to first MV beam-on was 9 minutes.
• Time from modeling image acquisition to beam-on was 3 minutes.

Conclusions:

• The clinical version of the Vero tumor tracking system, with automatic fiducial marker detection, is functional.
• The system's performance is adequate for progression to final commissioning and patient treatments.
• This study supports the clinical utility of advanced dynamic tumor tracking in radiation oncology.