PET/CT geometric registration method and system

The invention discloses a PET/CT geometric registration method and system. The method includes the steps that conventional imaging scanning and establishment are conducted on geometric body models through a CT machine, so that a CT reestablished image is acquired; a lutetium background conforming event of the geometric body models is scanned and reestablished through a PET instrument, so that a lutetium background conforming image is acquired; the gravity center of each geometric body in the CT reestablished image and the lutetium background conforming image is extracted; according to the gravity centers of the geometric bodies, gravity center mapping data of the CT reestablished image and the lutetium background conforming image are acquired; according to the gravity center mapping data, a rotation matrix and a horizontally-moving vector from the lutetium background conforming image to the CT reestablished image are acquired and serve as registration parameters from a PET image to a CT image. By the adoption of the method, PET/CT geometric registration can be conducted, the method can be used for regular calibration of a machine, a multi-point or multi-line positive electron source does not need to be prepared, the price of the geometric body models is low, the geometric body models can be reused, and an operator is merely irradiated.