1127 - A Comprehensive Motion Management System Including Oxygen Enhancement

Purpose/Objective(s): A comprehensive motion management system has been designed and implemented in-house to study and optimize breathing during beam delivery. It is comprised of: (1) real-time motion tracking using optical surface imaging and gas flowmeters, (2) accelerator beam gating, (3) vital sign monitoring, (4) biofeedback-based training tools, (5) oxygen-enhanced breathing gas, and (6) synchronized timelines with parallel signal processing.

Materials/Methods: Infrared cameras monitor thoracic and abdominal displacement. The ultrasonic flowmeter measures gas velocity with volume calculated via velocity-time integration. Analog circuits control beam gating and a signal congruency safety interlock. EtCO₂ is measured with an infrared sensor placed around the gas path. ECG signals are acquired using a 3-lead electrode array, dual-wavelength spectroscopy measures fingertip oxygen saturation, and pulse-by-pulse blood pressure is determined through Pulse Transit Time (PTT) or single-channel photoplethysmography (PPG) feature extraction. Augmented reality (AR) glasses display real-time and training respiratory waveforms. For patients that cannot voluntarily meet the desired breathing constraints, a pneumatically controlled balloon valve can stop or start gas flow at the appropriate volumes. Oxygen is delivered from gas cylinders and valves. A field-programmable gate array (FPGA) enables parallel processing of all signals with synchronized timelines.

Results: The infrared camera system operates at a sampling frequency of 100 - 2000 Hz with a spatial resolution of 0.1 mm and can track 1 - 100 reflective markers simultaneously. The ultrasonic flowmeter achieves a volumetric flow measurement accuracy of ± 0.5%. The beam gating delay is 37.7 ± 5 milliseconds for beam on and 18 ± 2.3 milliseconds for beam off. The ECG captures P-wave, QRS complex, and T-wave morphologies and determines the heart rate with a precision of ± 1%. Pulse oximetry precision is ± 0.5%. The non-invasive pulse-by-pulse blood pressure is useful for monitoring rapid changes during breath hold procedures without disturbing the patient. The breathing training curve assists the patient in reproducing the breathing pattern and achieving the anatomical position within the intended tolerance range. Interchangeable gas cylinders can provide different oxygen concentrations, while a positive-pressure unidirectional three-way valve assists inspiration. The balloon valve can stop or start gas flow within 50 milliseconds.

Conclusion: By observing and controlling multiple diverse parameters for individual patients, breath holding duration can be prolonged, positional reproducibility enhanced, efficiency increased, and patient safety maintained thereby providing a comprehensive solution for personalized respiratory motion management.