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

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.

In 13 volunteers (mean age 33.0 +/- 7.4 years), blood flow rates in the pulmonary artery (Qp), ascending aorta (Qs), and flow ratio Qp/Qs 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 x 2.1 mm vs. 2.3 x 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.

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 Qp/Qs by reference PC-MRI was 1.03 +/- 0.07 (range, 0.89-1.16), and 1.0 +/- 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 Qp/Qs 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 "30 seconds. High in-plane resolution was not advantageous.