A method and system for a gated radiation therapeutic system is provided. The method comprises performing a 4D-CT scan to obtain CT images, and processing the CT images to extract a characteristic signal, wherein the characteristic signal is associated with respiratory phases within the patients breathing cycle and has a correlation relation with the external signal of the gated radiation therapy. The method further comprises controlling a radiation beam for the gated radiation therapy based on the correlation relation between the characteristic signal and the external signal. The system comprises a 4D-CT scanner for performing a 4D-CT scan to obtain CT images and a characteristic signal extracting component for processing the CT images to extract a characteristic signal. The system further comprises a radiation control component for controlling a radiation beam for the gated radiation therapy based on the correlation relation between the characteristic signal and the external signal.
