Developing and Testing a Real-Time Collision Avoidance System for Couch and Gantry of a Linear Accelerator (LINAC)
Z Saleh1,2*, J Patrick1,2, E Klein1,2, (1) Rhode Island Hospital, Providence, RI, (2) Warren Alpert Medical School of Brown University, Providence, RI,
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PO-GePV-M-199 (Sunday, 7/25/2021) [Eastern Time (GMT-4)]
Purpose: Linear accelerators are equipped with safety mechanisms to avoid collision within the patient zone. However, they lack the safety features to detect collision between gantry and couch with the surrounding environment inside the treatment room. In this study, we present a low-cost solution for collision avoidance using commercially available sensors.
Methods: Two types of sensors were considered for this study. A low-cost ultrasonic distance sensor (HC-SR04) that provides a non-contact measurement for distances between 2 cm and 400 cm. A thin film pressure sensor (ZD10-100) for contact-based force-sensing measurement, which is rated at 500 grams. The pressure sensor was covered with a 5 mm layer of foam tape to transmit applied pressure to the force-sensitive resistor embedded inside the sensor. For testing purposes, the sensors were mounted at the base of the couch. The distance and force measurements were monitored in real-time (every 250 ms) by a micro-controller (Arduino Uno). The micro-controller was programmed to activate a trigger when the distance dropped below 3 cm or when a force was detected simulating a hard stop.
Results: The ultrasound sensor underestimated the distance over the measured range (3-50 cm) with an accuracy of 3-9 mm. The pressure sensor demonstrated high sensitivity when a small force was applied. The micro-controller successfully activated the trigger signal when an object was detected within 3 cm range or when an object came in contact with the pressure sensor.
Conclusion: We have demonstrated the feasibility of constructing a collision avoidance system using distance and force sensitive sensors. These sensors can be arranged in different configurations along the base of the couch and various locations along the gantry to achieve optimal performance. An industrial grade ultrasonic sensor is recommended for better stability and accuracy.
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