Abstract 677: Can Dual-Energy CT of the Heart Acquired at Rest Detect Reversible Ischemia Seen on Stress Myocardial Perfusion Imaging?
PURPOSE It has been proposed that dual-energy CT (DECT) can detect myocardial infarction in good correlation with fixed perfusion defects (PD) on SPECT myocardial perfusion imaging (MPI). However, whether DECT can detect reversible myocardial ischemia (RMI) has not been systematically investigated.
METHODS 36 patients (15 female, mean age 57±11 years) underwent stress/rest SPECT MPI and DECT of the heart with a dual-source CT system (A-tube: 140kV, B-tube 100kV). All CT scans were acquired at rest. DECT data was used to reconstruct anatomic coronary CT angiographic (CCTA) images and to map the myocardial iodine distribution representing the blood volume within the left ventricular myocardium. 13 patients subsequently underwent invasive coronary angiography (ICA). Two independent observers analyzed all DECT studies for stenosis and myocardial blood volume defects. Segmental comparison was performed between stress/rest SPECT PD and rest DECT blood volume defects and between ICA and CCTA for stenosis.
RESULTS On SPECT MPI, 17 patients had fixed myocardial PD in 89 myocardial segments and 13 had RMI in 68 segments. Blood volume defects on DECT acquired at rest correctly identified 85/89 (96%) of segments with fixed and 60/68 (88%) with reversible PD. Overall, DECT had 92.4% sensitivity and 93.4% specificity with 93.1% accuracy for detecting any type of myocardial PD seen on SPECT. On a per patient basis blood volume defects at DECT correctly identified 16/17 patients (94%) with fixed and 13/13 patients (100%) with reversible PD. Inter-observer agreement was good (weighted κ=0.87). Compared with ICA, CCTA had 90.2% sensitivity, 93.9% specificity and 92.9% accuracy for detection of >50% stenosis.
CONCLUSION In addition to diagnosing coronary artery stenosis and myocardial infarction, DECT acquired at rest has relatively high accuracy for the detection of RMI seen during stress induced hyperemia at SPECT MPI. This phenomenon may be explained by the higher spatial resolution of CT and the intrinsic vasodilatory effect and particular tissue kinetics of contrast media. Initial results warrant more systematic investigation of iodine tissue kinetics in the myocardium to better understand the clinical implications of these observations.