Comparison of Cartesian, UTE radial, and spiral phase-contrast MRI in measurement of blood flow in extracranial carotid arteries: normal subjects

Abstract

Use of Phase contrast (PC) MRI in measurement of blood flow has significant clinical importance. In this paper, we compare the accuracy of the conventional approach to flow imaging to two de novo approaches in 3 normal subjects in the common, internal, and external carotid arteries and discuss and demonstrate the advantages and disadvantages of each method. The conventional PC sequence adopts a Cartesian read-out in k-space and requires longer acquisitions but exhibits flow artifacts in the setting of stenotic and disturbed flow. Spiral PC collects k-space data using spiral readout and is capable of reducing the TR and TE in order to minimize the total imaging time. Despite its efficiency in scan time, in the single shot mode, this technique suffers from off-resonance and inconsistent data artifacts. Use of multiple short spiral arms for providing k-space coverage resolves these issues. Ultra short TE (UTE) PC MRI is a novel technique which adopts a radial trajectory and provides improvements to the standard radial acquisition by reducing the echo time to less than 1 ms through combination of flow encoding and slice select gradients and by immediate sampling of the FID during readout. The ultra-short echo times, improves on intravoxel spin dephasing due to fluid mixing observed in imaging of disturbed flow and stenotic jets. Despite its capability of achieving the shortest TE, this method is hindered by longer acquisition times and phase corruption errors. We mitigate this by a novel 3-D acquisition which includes a phase correction step. All three approaches were found to be able to quantify the normal Carotid flow waveform with high accuracy.