Isolating the cardiac blood pool position for use as a marker of heart position in free-breathing MRI examinations

Chest motion due to patient breathing can give rise to artifacts during conventional cardiac examinations by Magnetic Resonance Imaging (MRI). Typically, patients are asked to hold their breath during MRI exams to alleviate this problem. However, this can be difficult for sick patients and children, and has also been shown to affect physiology. This article outlines an approach to isolate the position of the blood pool in the heart ventricles and utilizes this position to mark the location of the heart during MRI examinations. A profile registration algorithm is used to shift image slices to the correct position by determining the displacement of the blood pool profile from the initial reference position. This approach is used in a prospective mode with slice tracking to correct the image slice position. Utilization of this approach eliminates uncertainties in correlating diaphragm motion with heart motion, and the need for the patient to breathhold.