822 THE JOURNAL OF NUCLEAR MEDICINE

This paper describes experimental results on the image resolution and uniformity improvement in single photon emission computed tomography (SPECT) with a noncircular detector orbit, implemented by a combi nation of rotational and translational motions, compared with a circular orbit. Earlier simulations performed by us (1) indicated that a noncircular detector orbit achieved by the above mo tions would give significantly improved resolution and uniformity. The resolution improvement occurs because the detector is brought closer to the patient with respect to the depth-dependent collimator resolution. The uni formity improvement is due to the shifting of the detector center relative to the object center as the detector is ro tated, which results in smearing of central-ring artifacts. This shift results from the translational component of the motion. SPECT resolution is fundamentally limited by the planar projection resolution, which is determined largely by the collimator resolution. Narrowing the gap betwee