Patent ID: 8718973

Claim:
A method for calculating distance ratios used to calculate a geometric probability between a voxel and a tube-of-response (TOR) defined by two crystals within a reconstruction space of a medical imaging apparatus, the method comprising: determining a first edge line connecting respective left endpoints of the two crystals in an X-Y plane of the medical imaging apparatus, the first edge line including a first middle point located midway between the left endpoints; determining a second edge line connecting respective right endpoints of the two crystals in the X-Y plane, the second edge line including a second middle point located midway between the right endpoints; determining a middle line of the TOR in the X-Y plane as a line intersecting the first middle point and the second middle point; projecting, in the X-Y plane, a first center point of a first surface of the voxel to the middle line along a direction of the first edge line to define a first projected point; projecting, in the X-Y plane, a second center point of a second surface of the voxel to the middle line along a direction of the second edge line to define a second projected point; calculating a first distance between one of the first and second middle points and the first projected point, and a second distance between the one of the first and second middle points and the second projected point; and determining a first distance ratio in the X-Y plane based on the first distance and the second distance.