Increased sensitivity through use of overlapping 180° orbits in clinical myocardial perfusion imaging

Clinical cardiac imaging is hindered by noise due to limited activity and imaging time. Use of 90° dual detector systems with 90° gantry rotation may provide the best sensitivity/resolution for cardiac imaging, but this option is not available to those using a triple-detector system with detectors at 120° intervals. This study utilizes a cardiac/chest phantom to compare several triple-detector orbits, with assessment of sensitivity and resolution. A 180° rotation with reconstruction of two of the three heads was evaluated, resulting in overlapping 180° orbits; use of a starting angle of 165° for the first head placed the overlapping portion of the orbits over the LAO myocardial region, where camera-cardiac distance is most favorable. Use of this overlapping orbit yielded resolution equivalent to a conventional (single-head) 180° rotation. Sensitivity was 90% of that of a 90° dual-detector system, and 20% better than the common practice of using a 120° orbit with reconstruction of 1 and 1/2 heads to achieve a 180° orbit. Use of 36O° acquisition with reconstruction of all three heads provided the greatest sensitivity, though at some loss in image quality. Thus, far those centers performing cardiac imaging using a triple detector system, using overlapping 180° orbits is the preferred acquisition choice