Systems and methods for determining an ROI of a subject are provided. In some embodiments, the system may obtain a target image including the subject situated on a table. The system may also obtain a focus position associated with the ROI of the subject to be scanned or treated by a medical device in the target image. The system may further determine a target table position based on the focus position. In some embodiments, the system may obtain a model image corresponding to the subject. The system may also obtain a virtual area corresponding to a virtual ROI in the model image. The system may also obtain a positioning image of the subject. The system may further determine, in the positioning image, a target area corresponding to the ROI of the subject corresponding to the virtual ROI based on the virtual area and the positioning image.
