Blood flow quantification in adults by phase-contrast MRI combined with SENSE -: a validation study

Purpose. To evaluate the feasibility of rapid free-breathing phase-contrast MRI (PC-MRI) at different in-plane resolutions combined with sensitivity encoding ( SENSE) for flow quantification in the great arteries in healthy adult volunteers. Methods. In 13 volunteers ( mean age 33.0 +/- 7.4 years), blood flow rates in the pulmonary artery (Q(p)), ascending aorta (Q(s)), and flow ratio Q(p)/Q(s) were determined by PC-MRI with SENSE reduction-factor 2 and 3 (SF-2, SF-3). Additionally, we used PC-MRI with higher spatial in-plane resolution (1.6*2.1 mm vs. 2.3*3.1 mm) with/without SF-3. Standard (= reference) PC-MRI, which used two excitations (NEX = 2), was compared with PC-MRI sequences with NEX = 1. Results. Reduction of signal averages and application of SENSE accelerated flow measurements by a factor of 3.8 (5.5) using PC-MRI with SF-2 (SF-3): Scan time was 36 sec (SF-2) and 25 sec (SF-3) at average heart rate of 69/min. The mean Q(p)/Q(s) by reference PC-MRI was 1.03 +/- 0.07 ( range, 0.89 - 1.16), and 1.08 +/- 0.11 ( range, 0.86 - 1.24) by PC-MRI + SF-3, respectively. For blood flow rate through the pulmonary artery and aorta, and for Q(p)/Q(s) ratio, we found differences of - 3% to + 4%. The lower limits of agreement ( mean - 2 SD) ranged between - 14% and - 21%, and upper limits ( mean + 2 SD) between + 9% and + 30%, demonstrating clinically acceptable agreement with standard PC-MRI (Bland-Altman analysis). PC-MRI at higher in-plane resolution both with/without SENSE yielded slightly smaller aortic and pulmonary flows ( mean differences 5% to 7%, p < 0.05). Conclusions. In adults, PC-MRI may be safely combined with SENSE to reduce scan time for a quantitative flow measurement in the great arteries to similar to 30 seconds. High in-plane resolution was not advantageous.