Purpose: To develop MR-tracked catheters to delineate the three-dimensional motion of coronary arteries at high spatial and temporal resolution.
Materials and methods: Catheters with three tracking microcoils were placed into nine swine. During breath-holds, electrocardiographic (ECG)-synchronized 3D motion was measured at varying vessel depths. 3D motion was measured in American Heart Association left anterior descending (LAD) segments 6-7, left circumflex (LCX) segments 11-15, and right coronary artery (RCA) segments 2-3, at 60-115 beats/min heart rates. Similar-length cardiac cycles were averaged. Intercoil cross-correlation identified early systolic phase (ES) and determined segment motion delay.
Results: Translational and rotational motion, as a function of cardiac phase, is shown, with directionality and amplitude varying along the vessel length. Rotation (peak-to-peak solid-angle RCA approximately 0.10, LAD approximately 0.06, LCX approximately 0.18 radian) occurs primarily during fast translational motion and increases distally. LCX displacement increases with heart rate by 18%. Phantom simulations of motion effects on high-resolution images, using RCA results, show artifacts due to translation and rotation.
Conclusion: Magnetic resonance imaging (MRI) tracking catheters quantify motion at 20 fps and 1 mm(3) resolution at multiple vessel depths, exceeding that available with other techniques. Imaging artifacts due to rotation are demonstrated. Motion-tracking catheters may provide physiological information during interventions and improve imaging spatial resolution.