Magnetic Resonance Imaging (MRI) has become the gold standard for the quantitative assessment of cardiac structure and function. The key to imaging the moving myocardium is a reliable and robust electrocardiogram signal which, used as a """"""""trigger,"""""""" can provide images at specified phases throughout the cardiac cycle. Stronger field strength magnets, greater magnetic gradient slew rates, and an ever increasing number of magnetic gradient pulse sequences such as those that provide cardiac perfusion have significantly increased the difficulties of triggering. In addition, individuals with sick hearts may have abnormal ECGs. The focus of this Phase II project is to research, develop and clinically evaluate our innovative real-time, reliable and robust system for ECG triggering during cardiac MR imaging. The project has four specific aims. The first three, aimed at developing an effective MR ECG triggering system, are: 1) to optimize the Phase I prototype MRI ECG data acquisition, fiberoptic transmission system; 2) to optimize, evaluate and test our adaptive noise cancellation methods to remove the RF and magnetic gradient artifacts that overwhelm ECG detection, and 3) to develop a """"""""real-time"""""""" embedded computer ECG trigger system and integrate it into a cardiovascular MR imaging system. Our last specific aim is to clinically analyze and evaluate the effectiveness of our MRI ECG trigger system. Our preliminary results illustrate the effectiveness of our methods in reliably detecting the ECG during MR imaging. Our methods include generating a novel optimal ECG vector for detection, and applying effective adaptive noise cancellation methods to extract the ECG R-wave from RF and gradient artifacts. Additional preliminary data demonstrates the capability of our optical telemetry system to transmit the ECG from the magnet and mitigate against the MR artifacts which corrupt the ECG signal. During Phase II, we will evaluate the performance of our triggering system using normal human subjects and a recorded data base of ECG arrhythmias and other defects. Our approach should provide a reliable and robust ECG trigger with minimal delay from the onset of the R-wave. Such a trigger would minimize blurring artifacts from cardiac and respiratory motion and improve MR tagging studies. KEYWORDS: Cardiac Magnetic Resonance Imaging, Magnetic Resonance ECG Triggering (Gating), ECG detection, cardiac imaging (MRI). ? ? ?
