A method for fiducial-less real-time motion tracking of abdominal tumors based on the correlation between the patients breathing pattern and the diaphragm/lung border during treatment delivery. This invention utilizes an edge detection technique to delineate the diaphragm/lung border on radiographic images in order to calculate or determine tumor locations in the abdomen. The position of the diaphragm/lung border is synchronized with the breathing pattern obtained from continuous optical monitoring of a patients respiratory cycle. The real-time optical breathing pattern obtained from monitoring is used to determine or calculate the position of the diaphragm/lung border during treatment delivery. The position of the diaphragm/lung border is then used to determine the tumor location in real-time. The target tumor coordinates generated through this process are used by the treatment delivery system to adjust the radiation beam geometry of the treatment delivery system to follow the tumor in real-time and accurately deliver radiation dose.
