Assessment of blood flow velocity profiles in heart ventricles and aorta with phase contrast magnetic resonance imaging

Accurate measurement of blood flow is usually very difficult and invasive to make in spite of its important roles in clinical diagnosis. Therefore, an alternative method capable of determining the cardiac output non-invasively will be of good use. Furthermore, measurement of blood velocity with high resolution either in the heart or in any part of circulatory system without any cardiac catheterization would play an important role in the evaluation of patients with circulatory disorders. The MRI phase contrast technique (PC-MRI) can be used for this purpose. It can provide flow velocity information in addition to anatomic imaging by applying bipolar gradient in the velocity encoding direction. We can obtain velocity encoded MR images computed by the phase difference between two images acquired with different gradient first moments but identical zeroth moments. We combined phase contrast sequence and cine method to acquire the velocity map across the entire cardiac cycle. ECG gating was used for triggering. We calculated volume flow by pixel unit velocity analysis in the region of interest. Also by visualizing the velocity profile dynamically with 3D representation, we could assess more easily how the appearances of blood flow patterns are. The proposed method was tested both with a phantom where a pulsatile waveform was generated by ventricular assistance device and in vivo at the heart of normal volunteer on a GE 1.5 T scanner. As a conclusion, the dynamically represented 3D images obtained by the cine PC method could be confirmed as a good method for assessment of cardiac function.