The present invention relates to a device for detecting motion of a person. The present invention further relates to a system incorporating the aforementioned device and a corresponding method. The proposed device comprises a projection sweep unit configured to obtain image data comprising depth information corresponding to an image showing the patient and to generate one or more projection images of the patient for different viewpoints, a motion detection unit configured to detect motion of the patient in the one or more projection images and to generate one or more motion detection signals indicating if motion is detected or not in a respective projection image, and an analysis unit configured to detect and localize body movements of one or more body parts of the patient based on one or more combinations of motion detection signals.