An in vivo validation of quantitative blood flow imaging in arteries and veins using magnetic resonance phase-shift techniques.

Abstract

Magnetic resonance (MR) techniques have recently been introduced, allowing quantitative measurement of blood flow with high spatial and temporal resolutions. These techniques are based on the phase of the MR signal rather than on the amplitude, and are referred to as MR phase or velocity mapping. Clinical validation is still lacking. We therefore performed an in vivo validation of such a technique in 17 healthy volunteers. Velocity maps were acquired at 50 ms intervals over the cardiac cycle in the aorta, superior and inferior vena cava. Plots were made of flow velocity and volume flow vs time and used for calculation of left ventricular stroke volume (SV), cardiac output (CO) and venous return. Comparison with Doppler ultrasound (x) yielded y = -7.5 + 1.1x (r = 0.76) for SV measurements (ml), and y = 0.3 + 0.9x (r = 0.86) for CO calculations (1 min-1). Comparison between MR SV (x) and MR determination of venous return (y), obtained by summation of the flow volumes per cardiac cycle in the superior and inferior vena cava, was close to identity, y = 1.3 + 1.0x (r = 0.91). Also, preliminary applications are presented in patients with aortic diseases. The findings of this study show that magnetic resonance velocity imaging can be accurately applied in vivo as a non-invasive means of measuring flow.