Preliminary Study of the Intel RealSense D415 Camera for Monitoring Respiratory like Motion of an Irregular Surface

Motion of the tumour during a radiotherapy treatment can compromise the clinical outcome for the cancer patient. To address this challenge the suitability and performance of the Intel RealSense™ D415 depth camera has been investigated as a tool for measuring the respiratory motion of the body surface. The precision of the camera depth data has been characterised as a function of the measurement distance up to 1.2 meters from a stationary and moving surface. The latency of the camera system was also measured. The average standard deviation of depth data in stationary measurements ranged from less than 0.2 mm for the shortest camera-surface distance of 400 mm to 3 mm for a distance of 1200 mm. Similar accuracy is reported for the acquisition of breathing motion with a discrepancy from nominal amplitudes of around 0.5 mm and 5 mm for the two extreme measurement distances. No dependence on the measurement precision has been observed as a function of the motion pattern. Finally, the camera was shown to be able to measure the more patient-like motion of a deformable respiratory motion phantom with an amplitude of surface motion varying from 1.5 - 2.5 mm. Although noisier, the camera data showed good agreement when compared with a NDI Polaris Spectra system. The latency of the Realsense™ system was measured to be 68.6 ms ± 9.6 ms. The results of this work indicate that the D415 RealSense™ depth camera is capable of measurement of external respiratory type motion of an irregular surface.