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

Clinical cardiac imaging is hindered by noise due to limited activity and imaging time. Use of 90 degrees dual-detector systems with 90 degrees gantry rotation may provide the best sensitivity/resolution for cardiac imaging, but this option is not readily available to those using a triple-detector system with detectors at 120 degrees intervals. This study utilizes a cardiac/chest phantom to compare several triple-detector orbits, with assessment of sensitivity and resolution. A 180 degrees rotation with reconstruction of two of the three heads was evaluated, resulting in overlapping 180 degrees orbits; use of a starting angle of 165 degrees 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 degrees rotation. Sensitivity was 87%-90% of that of a 90 degrees dual-detector system, and 16%-20% better than the common practice of using a 120 degrees orbit with reconstruction of 1 1/2 heads to achieve 180 degrees of data. Use of 360 degrees acquisition with reconstruction of all three heads provided the greatest sensitivity, though at the expense of some loss in image quality. Thus, for those centers performing cardiac imaging using a triple-detector system, use of overlapping 180 degrees orbits is the preferred acquisition choice.