Hybrid cardiac SPECT/64-slice CTCA imaging: Technical feasibility and initial clinical experience

Abstract

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Objectives: CT coronary angiography (CTCA) provides noninvasive diagnosis of coronary stenosis. Myocardial perfusion imaging using SPECT assesses the physiologic significance of coronary lesions. A hybrid research SPECT/CT device [GE Healthcare, Waukesha, WI, USA] combines a dedicated cardiac SPECT camera (Ventri) and a 64-slice CT (Lightspeed VCT) and enables concurrent assessment of myocardial perfusion and coronary anatomy. Methods: Thirty five patients (pts) with chest pain, M=25, age 37-77y, underwent stress-rest SPECT/64-CTCA imaging using Tc-MIBI within the first 8 weeks following the installation of the hybrid device. 14/140 coronary segments and 3/35 pts were excluded from the study due to technical inadequate CTCA. Segment-based analysis assessed the presence of myocardial ischemia on SPECT (reversible perfusion defect) and coronary stenosis on CTCA (narrowing >50%) in 126 segments in 32 pts. Left ventricular ejection fraction (LVEF) was measured on both SPECT and CT. Results: Fused SPECT/64-CTCA was of high technical quality in all 32 pts. 108/126 coronary segments (86%) in 18/32 pts (56%)showed normal perfusion and coronary anatomy. SPECT/64-CTCA demonstrated the absence of ischemia in related territories of 7 narrowed vessels in 7 pts, and the absence of significant stenosis on CT in 4 pts with 5 ischemic segments. No further invasive procedures were deemed necessary in these 11 pts. SPECT/64-CTCA enabled accurate registration of 6 coronary lesions to the related ischemic territories in 3 pts, indicating the need for therapeutic catheterization and intraluminal stenting. SPECT and CT measured LVEF showed a good correlation (r=0.90). Conclusions: Initial clinical experience indicates that single-session SPECT/64-CTCA is a technically reliable, noninvasive modality for diagnosis of hemodynamically significant coronary lesions. Cardiac SPECT/64-CTCA demonstrates the ischemic significance of coronary stenoses and may thus provide objective parameters representing the future decision making tools with respect to the need and planning of the interventional therapeutic approach in a particular occluded vessel.