Correlation of cine MR velocity measurements in the internal carotid artery with collateral flow in the circle of willis: Preliminary study

Abstract

The velocity-phase relationship intrinsic to phase-contrast magnetic resonance (MR) angiography permits the quantitative and qualitative assessment of blood flow. The ability to measure velocity and vessel cross-sectional area allows noninvasive assessment of volume flow rate (VFR) in the internal carotid artery (ICA). Phase-contrast techniques also demonstrate flow direction. Using two-dimensional cine phase-contrast angiography, the authors evaluated VFR in the ICA and collateral flow about the circle of Willis in 15 patients with ischemic neurologic symptoms. The VFR in each carotid artery was correlated with the degree of stenosis and presence or absence of abnormal circle of Willis collateral flow. There was a correlation between a decrease in VFR and abnormal circle of Willis collateral flow. In addition, a correlation between severe stenosis and a decrease in VFR was found. In patients with ischemic neurologic symptoms without severe stenosis (< 70% diameter stenosis), no decrease in VFR was seen. It is hoped that flow quantification and directional flow imaging with phase-contrast angiography will help further characterize carotid artery occlusive disease by enabling assessment of VFR changes associated with ischemic neurologic symptoms. This study also supports the hypothesis that two mechanisms--hemodynamic and embolic--play a role in ischemic neurologic symptoms.

Magnetic resonance angiographic evaluation of circle of Willis: A morphologic study in a tertiary hospital set up

“…MRA has demonstrated high sensitivity in evaluation of component vessels in the CW. [ 29 ] Though well-accepted clinically, sensitivity of 3D time-of-flight (TOF) MRA depends on the blood flow velocity of the vessel, and the technique may have difficulties in visualizing small vessels in the CW with slow or turbulent flow. [ 34 ] In most studies, MRA 3D acquisitions were made with either steady state precession (FSSP) or spoiled gradient technique (SPGR) using 1.5-tesla systems.…”

“…Recent studies have investigated the role of the CW in the development of collateral flow in ICA obstruction; these studies were based on mathematical models[ 17 18 19 ] and used transcranial Doppler ultrasound,[ 20 21 22 23 24 25 ] digital contrast–enhanced angiography,[ 3 26 ] or magnetic resonance angiography (MRA). [ 2 3 27 28 29 ] MRA has previously been shown to be well-suited to investigate the CW, in view of the fact that it is able to provide morphological as well as hemodynamic information concerning blood flow direction in individual vessels accurately. [ 30 31 ] Previous studies have demonstrated that three-dimensional time-of-flight (3D-TOF) MRA is a sensitive, noninvasive modality suitable for detecting the anatomy of the CW in healthy volunteers and patients with carotid artery disease.…”

Characterization of the time course of the superior mesenteric, abdominal aorta, internal carotid and vertebral arteries blood flow response to the oral glucose challenge test using magnetic resonance imaging

“…The imaging parameters of the cine PC-MRI sequences in the neck and the abdomen were chosen as a compromise between the need for spatial resolution to minimize partial volume effects and to maximize high-frequency sampling of volumetric blood flow cine PC-MRI measurements at both positions (Jiang et al 2007). The initial parameters chosen were similar to those typically employed in measurements using cine PC-MRI in the measurement of ICA (Davis et al 1993, Buijs et al 1998, Ford et al 2005, Oktar et al 2006 and those used for fast cine PC-MRI of the AA (Caruthers et al 2003, Lin et al 2004, Waters et al 2005, Grotenhuis et al 2006. These parameters were then modified by reducing spatial resolution to increase the speed of acquisition and optimized to maximize relative signal intensity differences of stationary and flowing tissue, which has been shown to help reduce the impact of partial volume effects (Jiang et al 2007).…”

“…Initial cine PC-MRI parameters for measuring flow in ICA and VA were selected from the literature (Davis et al 1993, Buijs et al 1998, Ford et al 2005, Oktar et al 2006: a Turbo Field Echo (TFE) sequence with linearly filled, Cartesian k-space, TE 3.2 ms, TR 15 ms, flip angle 15 • , field of view 200 × 170 cm, slice thickness 10 mm, SENSE factor 2, velocity sensitivity (VENC) 70 cm s −1 each single cine PC-MRI yielding 20 cardiac phase measurement points reconstructed retrospectively per R-to-R cardiac interval. This multi-shot TFE sequence acquires 2 k-space lines within a segment duration of twice the repetition time, yielding an acquired temporal resolution of 60 ms.…”

Phase-contrast magnetic resonance imaging of intracranial and extracranial blood flow in carotid near-occlusion

“…Such flow rates are of arterial perfusion, not of brain regional perfusion. Phase-contrast MRI studies have virtually unanimously found an association between an increasing degree of carotid stenosis and a reduction in flow rates through the internal carotid artery (ICA) and, when assessed, increased collateral use [ 4 – 15 ]. However, until recently, no PC-MRI studies assessed near-occlusions separately.…”