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A Low-Cost Perturbation Detection System for Surface Guided Radiation Therapy Cameras

J Patrick1,2*, Z Saleh1,2, U Langner1,2, C Collins1,2, J Brindle1,2, E Klein1,2, (1) Rhode Island Hospital (2) Warren Alpert Medical School of Brown University, Providence, RI


(Sunday, 7/12/2020)   [Eastern Time (GMT-4)]

Room: AAPM ePoster Library

Purpose: Guided Radiation Therapy (SGRT) is a stereo-vision camera system used to monitor patient surfaces for both patient setup and motion management during radiation therapy. Daily QA measurements are taken to ensure accurate alignment of each camera. In locations prone to vibration from external factors such as nearby construction or seismic activity, camera alignment can be perturbed after QA measurements have been taken. The purpose of this work is to develop and validate a low-cost monitoring system to detect and report when perturbation events change the alignment of the cameras, signaling the need for re-calibration.

Methods: detection system uses a 3-axis digital accelerometer (ADXL345, Analog Devices) with a sensitivity of ±2 g (19.6 m/s^2) to collect measurements every 100 milliseconds, which are transmitted with timestamp to a serial Bluetooth receiver. Both digital accelerometer and Bluetooth transmitter/receiver are low power consumption components running on an open-source electronic prototyping platform (Arduino), designed to be mounted to the outside of an SGRT camera. Daily QA measurements were recorded 3 times daily (morning, afternoon, evening) and changes in RMS error values were correlated with perturbation events recorded by the detection system.

Results: from our perturbation detection device show strong correlation with changes in RMS error during Daily QA measurements of the SGRT system. An acceleration of 20 m/s^2 was correlated with a 0.5 mm RMS error on the SGRT system. An RMS error of 1 mm requires a re-calibration and correlated events can alert users when such events occur.

Conclusion: real-time monitoring system for SGRT cameras was developed using a low-cost open-source electronic prototyping platform. Detection of events resulting in misalignment of SGRT cameras can be detected in real-time, alerting users to the need for a re-calibration before treatment.

Download ePoster [PDF]


Surface Matching, Quality Control, Setup Errors


TH- RT Interfraction Motion Management: Development (new technology and techniques)

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