Measurement of coronary blood flow and flow reserve using magnetic resonance imaging

Purpose: It was the purpose of this study to demonstrate the feasibility of performing coronary artery flow and coronary flow reserve (CFR) measurements in normal human volunteers using a magnetic resonance (MR) phase contrast technique. Materials and Methods: Coronary flow rate, flow velocity, peak flow and CFR were determined at rest and during pharmacologically induced hyperemia in 10 healthy volunteers. The flow measurements were obtained during a single breath-hold by using a fast, prospectively gated, segmented k-space gradientecho phase contrast acquisition with view sharing (FAST-CARD PC) that was modified to improve sampling of the diastolic flow. Data were processed using the standard phase difference (PD) processing techniques as well as a new complex difference (CD) flow measurement method intended to improve the accuracy of flow measurements in small vessels. Results: Mean hyperemic flow velocity (40 ± 16 cm/s) and blood flow (3.9 ± 1.5 m1/s) rates differed significantly from resting velocity (13 ± 6.6 cm/s) and flow (1.1 ± 0.4 ml/s) measurements (p < 0.0001). PD methods consistently measured larger flow rates at rest (24% larger, p < 0.0005) and stress (29% larger, p < 0.0001). CFR, calculated as the ratio of the mean PD flows (4.7 ± 2.8), was higher than CFR calculated as the ratio of mean CD flows (4.2 ± 1.8); however, the differences did not reach statistical significance (p = 0.07). Flow measurements performed in adjacent slices of the same vessel correlated well (r = 0.88). Conclusions: Coronary flow and CFR measurements using the MR techniques are feasible and are similar to those reported in the literature for healthy volunteers.