Detector arrangement and sampling characteristics in rotary positron-emission computed tomography.

A rotary positron-emission computed tomography system has been proposed in which detectors are mounted unequally spaced on a ring, so as to provide fine and uniform linear sampling during a 360 degree rotation of the ring around its centre. The usefulness of a simple iterative method for searching for a suitable arrangement of detectors is shown, and the dependence of sampling characteristics of such an arrangement on various parameters is clarified. These parameters include the number of detectors I, and the gaps between the adjacent detectors (referred to as angular separations). It is concluded that if the sum total of the angular separations is approximately larger than the angle A subtended at the centre by one detector unit (i.e. if 360 degree -IA greater than or equal to A), a detector arrangement having satisfactory sampling characteristics for positron reconstruction tomography can be determined. Using this iterative method, a 64-detector arrangement of a prototype rotary positron ECT system named POSITOLOGICA was designed and found to be almost optimal under the given conditions.