Abstract 3826: Prospectively ECG-Gated Multidetector Computed Tomography Viability Imaging Accurately Quantifies Infarct Size While Lowering the Radiation Dose by an Order of Magnitude
Background: We have previously demonstrated that retrospectively gated (RG) delayed enhanced multidetector computed tomography (de-MDCT) accurately quantifies infarct size compared with histopathology. However, the large radiation dose requirement for RG scans limits clinical utility, especially in patients undergoing MDCT coronary angiography. The purpose of this study was to compare the accuracy of a prospectively gated (PG) de-MDCT imaging protocol to RG de-MDCT imaging for the assessment of infarct size following myocardial infarction.
Methods and Results: Five porcine models of anterior myocardial infarction were imaged 10 minutes following the injection of 150 ml of iopamidol (370 mg I/ml) using both a PG de-MDCT protocol (detector collimation = 3 mm X 4, 135 kV, 150 mA, cardiac phase = 50%) and a RG de-MDCT protocol (detector collimation = 0.5 mm X 64, 120 kV, 400 mA). Images were analyzed in the axial plane using a 3 mm slice thickness and a cardiac phase of 50%. Infarcts were defined as a signal density of one standard deviation above the remote myocardial signal density using a semi-automated software program and expressed as a percentage of total left ventricular myocardial volume. Mean myocardial mass was 49.1g and 48.5g (mean difference 0.6g, p=0.72) using PG and RG, respectively. Infarct size, expressed as a percentage of total myocardial volume, was 24.9% and 28.6% (mean difference: 3.7%, p=0.10), respectively. Contrast to noise ratios were similar for the PG and RG protocols: 1.7 and 1.6, respectively (p=0.13). Most importantly, the estimated radiation dose for the RG protocol was 17 mSv while that for the PG protocol was only 1.5 mSv.
Conclusions: Prospective ECG-gated delayed enhanced MDCT imaging following myocardial infarction accurately measures infarct size compared with retrospective ECG gated protocols using a relatively small radiation dose.