RESUMO
Physiologic motion of the heart is one of the major problems of myocardial blood flow quantification using first pass perfusion-MRI method. To overcome these problems, a perfusion pulse sequence with prospective slice tracking was developed. Cardiac motion was monitored by a navigator directly positioned at heart's basis to overcome no additional underlying model calculations connecting diaphragm and cardiac motion. Additional prescans were used before the perfusion measurement to detect slice displacements caused by remaining cardiac motion between navigator and the perfusion slice readout. The pulse sequence and subsequent quantification of myocardial blood flow was tested in healthy pigs with and without prospective slice tracking under both free-breathing and breath-hold conditions. To avoid influences by residual contrast agent concentration time courses were analyzed. Median myocardial blood flow values and interquartile ranges with prospective slice tracking under free-breathing and in a breath-hold were (1.04, interquartile range = 0.58 mL/min/g) and (1.20, interquartile range = 0.59 mL/min/g), respectively. This is in agreement with published positron emission tomography values. In measurements without prospective slice tracking (1.15, interquartile range = 1.58 mL/min/g), the interquartile range is significantly (P < 0.012) larger because of residual cardiac motion. In conclusion, prospective slice tracking reduces motion-induced variations of myocardial blood flow under both during breath-hold and under conditions of free-breathing.
