Patent ID: 8259897

Claim:
A method for determining a true central ray of scanning an object placed between a fixed x-ray source and a detector in a computer tomography system, the method comprising: producing a beam of x-rays from the fixed x-ray source; detecting the x-rays at the detector; receiving scanning projection data comprising a plurality of pixels of the object under examination; rotating the object under examination using a manipulator; selecting a first projection pixel position from the projection data, calculating a second projection pixel position, a gray level, and a projection angle for each pixel of the plurality of pixels for each one of a set of predetermined central rays; measuring a mismatching of gray levels of each pixel of the plurality of pixels and its corresponding second projection pixel for each one of the set of predetermined central rays; and identifying the minimum of the measurement of the mismatching as an estimate of the true central ray; wherein determining the first projection pixel position by defining a line formed with two points on the object, the line is aligned with the source and projected on the first projection pixel position; wherein for each predetermined central ray, each line on the object has a first projection position and second projection position during a 360° scanning that is aligned with the source; wherein determining the second projection pixel position by determining the line aligned with the source during scanning; and wherein the second projection pixel position is calculated with a known source-to-detector distance.