Comparative analysis of respiratory motion tracking using Microsoft Kinect v2 sensor

Abstract

PurposeTo present and evaluate a straightforward implementation of a marker‐less, respiratory motion‐tracking process utilizing Kinect v2 camera as a gating tool during 4DCT or during radiotherapy treatments.MethodsUtilizing the depth sensor on the Kinect as well as author written C# code, respiratory motion of a subject was tracked by recording depth values obtained at user selected points on the subject, with each point representing one pixel on the depth image. As a patient breathes, specific anatomical points on the chest/abdomen will move slightly within the depth image across pixels. By tracking how depth values change for a specific pixel, instead of how the anatomical point moves throughout the image, a respiratory trace can be obtained based on changing depth values of the selected pixel. Tracking these values was implemented via marker‐less setup. Varian's RPM system and the Anzai belt system were used in tandem with the Kinect to compare respiratory traces obtained by each using two different subjects.ResultsAnalysis of the depth information from the Kinect for purposes of phase‐ and amplitude‐based binning correlated well with the RPM and Anzai systems. Interquartile Range (IQR) values were obtained comparing times correlated with specific amplitude and phase percentages against each product. The IQR time spans indicated the Kinect would measure specific percentage values within 0.077 s for Subject 1 and 0.164 s for Subject 2 when compared to values obtained with RPM or Anzai. For 4DCT scans, these times correlate to less than 1 mm of couch movement and would create an offset of 1/2 an acquired slice.ConclusionBy tracking depth values of user selected pixels within the depth image, rather than tracking specific anatomical locations, respiratory motion can be tracked and visualized utilizing the Kinect with results comparable to that of the Varian RPM and Anzai belt.

The Importance of Respiratory Rate Monitoring: From Healthcare to Sport and Exercise

“…Depth sensors can also be used for respiratory motion tracking during radiotherapy. A good agreement was found between the Microsoft Kinect v2 and the more commonly used Anzai Respiratory Gating System and Varian's RPM system [262]. The characteristics and ease of use of depth sensors [262] provide interesting avenues for improving radiotherapy management.…”

Design and Evaluation of a MEMS Magnetic Field Sensor-Based Respiratory Monitoring and Training System for Radiotherapy

“…Using a Kinect v2 camera, Silverstein et al developed a system for monitoring respiration using information on the surface of the patient without markers and compared their system with existing commercial products, Varian’s Real-time Position Management (RPM) System (Varian Medical Systems, Palo Alto, CA, USA) and the Anzai belt system (Anzai Medical Co., Ltd., Tokyo, Japan). They reported that the period measurement error of their system was 77 ms to 164 ms [ 34 ]. According to the accuracy test of the RPM system used for respiratory monitoring in the present clinical cases, 99.9% of cases have an error of less than 2 mm [ 35 ].…”

Contactless Monitoring of Breathing Pattern and Thoracoabdominal Asynchronies in Preterm Infants Using Depth Cameras: A Feasibility Study

“…Structured light plethysmography is a contactless method that may overcome the abovementioned limitations [9] but is cumbersome and unsuitable for infants inside an incubator. Due to recent advances in camera technology and computer vision, researchers have developed compact and cheap contactless solutions to monitor respiratory activity [10] – [19] . Some of these solutions were designed for gating [14] , [16] and polysomnographic [11] , [17] applications and were validated in healthy adults [12] , [14] – [17] or children [11] , [13] .…”

“…Due to recent advances in camera technology and computer vision, researchers have developed compact and cheap contactless solutions to monitor respiratory activity [10] – [19] . Some of these solutions were designed for gating [14] , [16] and polysomnographic [11] , [17] applications and were validated in healthy adults [12] , [14] – [17] or children [11] , [13] . The infants’ small breathing movements and irregular breathing patterns limit the use of these tools in the NICU.…”