1126 - Pediatric Liver Treatment Utilizing Breath-Hold Techniques in Proton Pencil-Beam Scanning: Implementation of an Advanced Online Breathing Control and Monitoring System Compatible with CT and MRI
Presenter(s)
S. N. Huh1,2, R. Mailhot Vega1,2, J. Y. Park1,2, and P. Johnson1,2; 1Department of Radiation Oncology, University of Florida College of Medicine, Gainesville, FL, 2University of Florida Health Proton Therapy Institute, Jacksonville, FL
Purpose/Objective(s): We developed a prototype of a deep inspiration breath-hold (DIBH) system that includes a pressure sensor compatible with both CT and MRI, along with visual breathing guidance tailored for different breathing periods. It is designed to treat pediatric liver cancer using pencil-beam scanning (PBS) while incorporating custom patient immobilization for hand crossing grips and arm positioning. Additionally, we have outlined how MR and CBCT imaging can be integrated to enhance image quality for target localization and motion evaluation.
Materials/Methods: The prototype DIBH system consists of three main components: an arm position stand, a visual guide panel with its holder, and a pressure sensor that measures the patient's breathing amplitude. The sensor provides visual alerts whenever the breathing amplitude exceeds a predefined threshold. The materials and structures of the system are designed for use in CT and MRI imaging during patient simulation and treatment, specifically for evaluating and monitoring breathing motion. The patient’s breathing amplitude and frequency can be guided by modifying the lighting frequency and sequence of the visual aid pattern. Additionally, a hand-held emergency button is available for patients who are unable to maintain DIBH during treatment. Pressing this button promptly alerts the therapy team through a visual notification. The PBS plan uses three beam angles that can be delivered with one DIBH for each field by optimizing energy and spot spacing. By employing the DIBH system for kV and CBCT imaging during treatment, the patient's target is confirmed if it falls within the internal target volume. The system is also used in MR simulation to verify anatomical changes and responses of the target. The DIBH system was clinically tested in the treatment of an 11-year-old boy with liver cancer.
Results: This prototype effectively worked for the pediatric patient, allowing for a comfortable positioning and straightforward visual guidance to achieve the DIBH within 15 seconds. In comparison, MR scans performed in cine mode, both with and without the DIBH system, showed that the breathing amplitude could be reduced to half of that observed during free breathing. When evaluating motion in each treatment fraction using CBCT with DIBH, the maximum motion confirmed was less than 5 mm in peak-to-peak measurements. The patient exhibited no signs of duodenal complications during or after treatment. Additionally, by optimizing the CBCT scan parameters and incorporating a filter plus collimator (filtimator), the target volume was enhanced to ensure proper localization with an appropriate margin.
Conclusion: The DIBH system demonstrated feasibility and effectiveness for clinical use in pediatric patients, especially in assisting with breathing guidance. It enables safe applications in CT and MR simulations, as well as in-room imaging guidance, by confirming the localization of targets and reducing adjacent critical organs.