Quantitative rest/stress myocardial perfusion imaging with dynamic SPECT

Objectives The goal of this work is to quantitatively image myocardial perfusion at rest and stress with use of dynamic SPECT, and thereby obtain a more sensitive measure of myocardial ischemia in patients than is obtained by the present visual interpretation of static cardiac SPECT images.

Methods Two 30-min dynamic emission scans of a patient were acquired with use of a dual-head GE Millennium VH Hawkeye SPECT/CT scanner. The first scan was performed with the patient at rest, and was begun shortly before an injection of 3.6 mCi of Tl-201. The second scan was performed subsequent to pharmacologically induced stress, and was begun shortly before an injection of 24 mCi of Tc-99m-sestamibi. X-ray CT scans were performed before the first emission scan and after the second emission scan to obtain attenuation maps. Time-activity curves (TACs) for the blood and myocardium were estimated directly from the projection data. Compartmental modeling was then applied to the TACs to obtain quantitative estimates of the uptake rates of Tl-201 and Tc-99m-sestamibi in the myocardium.

Results Compartmental model analysis yielded uptake rate estimates (related to flow times extraction) of 0.33 and 0.18 per min at rest and stress, respectively. Adjusting for the fact that the extraction of Tl-201 at lower flows is 2-3 times greater than the extraction of Tc-99m-sestamibi at higher flows, this suggests that myocardial perfusion increased by a factor of 1.1-1.6 during stress.

Conclusions The results suggest that a quantitative measure of myocardial ischemia in patients can be obtained via rest/stress dynamic SPECT imaging and X-ray CT imaging performed during a 90-min study with current SPECT/CT scanners. Advances provided by new dedicated cardiac scanners should reduce the overall study time. These methods can also be applied to dynamic PET.

Research Support U.S. National Institutes of Health grants R01-EB00121, R01-EB007219, and R01-HL71253; U.S. Department of Energy contract DE-AC02-05CH11231