A computer implemented method and a medical imaging system for calibrating a motion detection system working according to a motion detection technique and configured for detecting a motion of an object during medical imaging by means of the medical imaging system, the computer-implemented method comprising an automatic calibration process for determining at least one motion threshold for said object motion detection system, said calibration process taking place for said object being in a position and place allowing its imaging by said medical imaging system, the calibration process comprising:a. using the motion detection system working according to said motion detection technique for repeatedly acquiring motion detection data enabling object motion detection and using a motion quantification system working according to a motion quantification technique for repeatedly acquiring motion quantification data enabling object motion quantification；b. analyzing the motion quantification data for determining if said object was mobile or immobile
