PCA based analysis of external respiratory motion using an RGB-D camera

Human respiration induces considerable external and internal motion in the thoracic and abdominal regions. Tracking and modeling of this motion is an important task for accurate treatment planning and dose calculation during external beam radiotherapy. Inaccurate motion tracking can cause severe issues such as errors in target/normal tissue delineation and increment in the volume of healthy tissues exposed to high doses. Different methods have been introduced to model the respiratory motion, but most of them use wearable markers or surgical node implanting techniques, which are inconvenient to patients. In this paper, we experiment the feasibility of using an RGB-D camera along with Principal Component Analysis (PCA) to track and model the subject-specific external respiratory motion. Marker-based depth frame registration technique is also introduced to limit the measuring area into an anatomically consistent region during the treatment. We evaluate the accuracy of the proposed method using a Spirometer and a laser line scanner.