James Duval Koonce MD, Presenter: Research Fellow, Siemens Medical Solutions in Forchheim, Germany

Bernhard Schmidt PhD, Abstract Co-Author: Employee, Siemens AG

Markus Weininger MD, Abstract Co-Author: Research support, Siemens AG

Gorka Bastarrika MD, Abstract Co-Author: Nothing to Disclose

Thomas G. Flohr PhD, Abstract Co-Author: Employee, Siemens AG

U. Joseph Schoepf MD, Abstract Co-Author: Speakers Bureau, Bracco Group Speakers Bureau, General Electric Company Speakers Bureau, Bayer AG Speakers Bureau, Siemens AG Medical Advisory Board, Siemens AG Medical Advisory Board, Bayer AG Research grant, Bayer AG Research grant, Bracco Group Research grant, General Electric Company Research grant, Siemens AG

Dual-energy CT (DECT) has been proposed for the evaluation of the myocardial blood supply; however, previous investigations used visual, qualitative assessment for detecting myocardial perfusion defects at DECT. We aimed at objectively measuring the myocardial iodine concentration as a surrogate for blood volume during stress and rest based on DECT.

In a pilot phantom experiment we calibrated the DECT iodine signal to known iodine concentrations in a given volume and established the reproducibility of these measurements. We then used the Perfusion Blood Volume software application to perform DECT-based measurements of the iodine concentration in healthy, ischemic, and infarcted myocardium of 9 patients who had undergone rest/stress DECT (Definition Flash, Siemens) of the heart as well as stress/rest cardiac perfusion MRI (CPMRI). The myocardial iodine concentration was then correlated with CPMRI up-slopes during stress and rest as well as with the subjective evaluation of CPMRI.

148/153 myocardial segments could be successfully processed. On CPMRI, 31/148 myocardial segments showed fixed perfusion defects and delayed enhancement indicating chronic infarction. 17/148 segments showed reversible perfusion defects without delayed enhancement indicating ischemia. In healthy myocardium, there was a significant (p<0.001) increase in mean iodine concentration of 0.52 mg/ml tissue between rest and stress measurements. Chronic infarcts showed no significant (p>0.05) differences in mean iodine concentration (0.22 mg/ml) between rest and stress. Ischemic segments showed a significant (p<0.001) decrease of 1.4 mg/ml in mean iodine concentration between rest and stress. These measurements showed fair correlation (r = 0.73-85) with CPMRI up-slopes during stress and rest and fair to excellent correlation (r = 0.87-0.93) with subjective CPMRI evaluation.

DECT measurement of myocardial iodine concentration shows promise for quantifying the extent and severity of ischemic heart disease and for estimating myocardial perfusion reserve in lieu of actual time-resolved perfusion imaging.

Using iodine concentration as a quantitative surrogate for perfusion could enhance the potential role of DECT as a stand-alone modality for integrative imaging of ischemic heart disease.

Koonce, J, Schmidt, B, Weininger, M, Bastarrika, G, Flohr, T, Schoepf, U, Quantitative Analysis of Myocardial Iodine Concentration during Stress and Rest Based on Dual-Energy CT: Comparison with Cardiac Perfusion MRI.  Radiological Society of North America 2010 Scientific Assembly and Annual Meeting, November 28 - December 3, 2010 ,Chicago IL. http://archive.rsna.org/2010/9007129.html