Patent ID: 7570737

Claim:
A cargo security inspection method using a security inspection system configured to perform spiral scanning for inspecting an inspected object, the cargo security inspection system comprising a radiation source for generating ray beams and a data collecting unit for collecting transmission projection data of the ray beams having transmitted through the inspected object, the method comprising: in step A: spirally scanning the inspected object at a first precision using a ray beam to transmit through the inspected object; and the data collecting unit obtaining a first transmission projection data of the ray beam transmitting through the inspected object; in step B, judging whether there is a suspect area in an inspected area according to the first transmission projection data, step C being performed conditional upon that the suspect area is judged to exist, and the inspection otherwise ending; in step C: scanning at least one slice of the suspect area at a second precision using the ray beam to transmit through the at least one slice; and the data collecting unit acquiring a second transmission projection data of the ray beam transmitting through the at least one slice, wherein the second precision is greater than the first precision; and in step D, constructing a tomographic image of the at least one slice using the second transmission projection data obtained in step C; wherein: in step A, a scanning trajectory of the ray beam on the inspected object is a spiral trajectory about the inspected object; the first precision is at a first pitch; the second precision is at a second pitch; and the first pitch is in the range of 5-10 relative pitch, and is substantially larger than the second pitch, resulting in an incomplete CT scanning in step A.