Cardiovascular Flow Measurement with Phase-Contrast MR Imaging: Basic Facts and Implementation

Abstract

Phase-contrast magnetic resonance (MR) imaging is a well-known but undervalued method of obtaining quantitative information on blood flow. Applications of this technique in cardiovascular MR imaging are expanding. According to the sequences available, phase-contrast measurement can be performed in a breath hold or during normal respiration. Prospective as well as retrospective gating techniques can be used. Common errors in phase-contrast imaging include mismatched encoding velocity, deviation of the imaging plane, inadequate temporal resolution, inadequate spatial resolution, accelerated flow and spatial misregistration, and phase offset errors. Flow measurements are most precise if the imaging plane is perpendicular to the vessel of interest and flow encoding is set to through-plane flow. The sequence should be repeated at least once, with a high encoding velocity used initially. If peak velocity has to be estimated, flow measurement is repeated with an adapted encoding velocity. The overall error of a phase-contrast flow measurement comprises errors during prescription as well as errors that occur during image analysis of the flow data. With phase-contrast imaging, the overall error in flow measurement can be reduced to less than 10%, an acceptable level of error for routine clinical use.

Assessment of pulmonary perfusion in a single shot using SEEPAGE

“…One inevitable problem is the fact that even in the diastolic cycle the flow in the main blood vessels (eg, aorta, pulmonary arteries, and veins) is not zero (25,26). Hence, even when data is collected solely in the diastolic period, flow effects lead to a signal dispersion that is always present during phase encoding.…”

The formation of cerebrospinal fluid: Nearly a hundred years of interpretations and misinterpretations

“…Phase-contrast magnetic resonance (MR) imaging is mainly used in cardiovascular imaging for obtaining quantitative information on blood flow. Some error in measurement is inevitable due to the technical limitations of this method, and for blood flow assessment it is estimated to be around 10% (Hoeper et al, 2001;Lotz et al, 2002). It is much more demanding to perform a precise measurement of CSF flow through the mesencephalic aqueduct.…”

Quantification of the pulse wave velocity of the descending aorta using axial velocity profiles from phase‐contrast magnetic resonance imaging

“…1a) that caused significant bias in the calculation of the PWVs. The phase-offset errors were considered to arise from noncompensated eddy-current-induced fields and concomitant gradient terms (19,20). To correct for the phase-offset errors, 12-18 regions in the fat or muscle of the body wall were selected from the magnitude images of PC-MRI (Fig.…”