The impact of different positions and thoracial restrains on respiratory induced cardiac motion.

One of the limiting factors for high resolution magnetic resonance coronary angiography (MRCA) is the motion of the heart during breathing. Current approaches use mainly motion correction in one dimension. We aimed to determine the relation between diaphragmatic motion and cardiac motion as well as the potential influence from external restraints reducing thoracical anterior posterior (AP) motion. Four real time navigators were used to collect motion parameters, diaphragmatic cranio-caudal, cardiac cranio-caudal, diaphragmatic anterior-posterior, and thoracical anterior-posterior. Measurements were performed in prone and supine position and supine position with a thorax restraint. In supine, the highest correlation was found between cranio-caudal diaphragmatic and cardiac motion (r2 = 0.71, slope = 0.26; p < 0.05). Prone positioning or external restraints led to significant changes of motion patterns, with a lower correlation between diaphragmatic and cardiac position. External manipulation of breathing by prone positioning or thoracical restraints leads to a less accurate prediction of cardiac position from assessment of diaphragmatic positions compared to standard supine positioning.