Article

Evaluation of intracranial stenoses and aneurysms with accelerated 4D flow

Department of Radiology, University of California San Francisco, San Francisco, CA 94143-0628, USA.
Magnetic Resonance Imaging (Impact Factor: 2.09). 08/2009; 28(1):41-6. DOI: 10.1016/j.mri.2009.05.042
Source: PubMed

ABSTRACT

The aim of this study was to evaluate intracranial arterial stenoses and aneurysms with accelerated time-resolved three-dimensional (3D) phase-contrast MRI or 4D flow. The 4D flow technique was utilized to image four normal volunteers, two patients with intracranial stenoses and two patients with intracranial aneurysms. In order to reduce scan time, parallel imaging was combined with an acquisition strategy that eliminates the corners of k-space. In the two patients with intracranial stenoses, 4D flow velocity measurements showed that one patient had normal velocity profiles in agreement with a previous magnetic resonance angiogram (MRA), while the second showed increased velocities that indicated a less significant narrowing than suspected on a previous MRA, as confirmed by catheter angiography. This result may have prevented an invasive angiogram. In the two patients with 4-mm intracranial aneurysm, one had a stable helical flow pattern with a large jet, while the other had a temporally unstable flow pattern with a more focal jet possibly indicating that the second aneurysm may have a higher likelihood of rupture. Accelerated 4D flow provides time-resolved 3D velocity data in an 8- to 10-min scan. In the stenosis patients, the addition of 4D flow to a traditional MRA adds the velocity data provided from transcranial Doppler ultrasound (TCD) possibly allowing for more accurate grading of stenoses. In the aneurysm patients, visualization of flow patterns may help to provide prognostic information about future risk of rupture.

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    • "To our knowledge, there has been no successful attempts to detect such flow instabilities in − vivo in sidewall (SW) aneurysms. Indeed, acquiring in − vivo hemodynamic data of IAs at the sufficiently high resolution to capture flow instabilities is technically challenging with the most advanced non-invasive techniques [23, 52, 53, 54]. To date, only high-fidelity numerical simulations [2, 32, 33, 51] and in − vitro experiments [60] have accomplished successful such attempts. "

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    • "It should be noted that similar 4D velocity mapping techniques have been applied in different vascular territories such as peripheral vessels [99], carotid arteries [25,100], large intra-cranial arteries [27,28,101,102], and to the velocities of myocardial movements and deformation [32-34]. 4D velocity acquisitions can be used independent from the used MRI platform without major differences with respect to possible implementations of the MR pulse sequence. "
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