Four-dimensional MRI flow examinations in cerebral and extracerebral vessels – ready for clinical routine?

Abstract

Purpose of review To evaluate the feasibility of 4D flow MRI for the clinical assessment of cerebral and extracerebral vascular hemodynamics in patients with neurovascular disease. Recent findings 4D flow MRI has been applied in multiple studies to qualitatively and quantitatively study intracranial aneurysm blood flow for potential risk stratification and to assess treatment efficacy of various neurovascular lesions, including intra-aneurysmal and parent artery blood flow after flow diverter stent placement and staged embolizations of arteriovenous malformations and vein of Galen aneurysmal malformations. Recently, the technique has been utilized to characterize age-related changes of normal cerebral hemodynamics in healthy subjects over a broad age range. Summary 4D flow MRI is a useful tool for the non-invasive, volumetric and quantitative hemodynamic assessment of neurovascular disease without the need for gadolinium contrast agents. Further improvements are warranted to overcome technical limitations before broader clinical implementation. Current developments, such as advanced acceleration techniques (parallel imaging and compressed sensing) for faster data acquisition, dual or multiple velocity encoding strategies for more accurate arterial and venous flow quantification, ultra-high field strengths to achieve higher spatial resolution, and streamlined post-processing workflow for more efficient and standardized flow analysis, are promising advancements in 4D flow MRI.

Assessing test–retest reliability of phase contrast MRI for measuring cerebrospinal fluid and cerebral blood flow dynamics

“…In another study, this technique was used to measure peak CSF flow at the craniocervical junction and cervical spinal canal in healthy individuals and those with Chiari malformations . However, while 4D flow MRI has shown great promise in understanding flow dynamics, long scan times (5‐20 min) and poor spatial resolution need to be addressed before it can be used as a routine clinical tool …”

Test–retest multisite reproducibility of neurovascular 4D flow MRI

“…17,18 In addition to assessment of the flow velocity, the 4D flow MRI technique allows for the evaluation of several additional hemodynamic parameters that may be derived from the velocity information, such as wall shear stress (WSS), 6,19 blood pressure difference, 20 turbulence kinetic energy, 21 and viscous energy loss, 22 etc. Previous studies have demonstrated clinical applications of this technique for improved characterization of hemodynamics in neurovascular systems, 1,23,24 intraheart and great vessels, 25 and peripheral vessels. 26 The validity and accuracy of 4D flow MRI has been demonstrated using 2D PC MRI, Doppler ultrasound, or catheter as references.…”

The Ring Vortex: Concepts for a Novel Complex Flow Phantom for Medical Imaging

“…where l is the diffusivity scale of the ring's core; 1 I is the first-order modified Bessel function; 2F2 is the generalized hypergeometric function.…”

“…However, the lack of a gold standard reference in such conditions often limits the degree to which inferred flow measures can be trusted, regardless of whether the flow is derived from computational or image-based approaches. We propose a new reference for complex flow imaging in the form of the ring 1 Quality Control (QC) refers to "part of quality management focused on fulfilling quality requirements"-ISO 9000 clause 3.2.10. Quality Assurance (QA) refers to "a part of quality management focused on providing confidence that quality requirements will be fulfilled"-ISO 9000 clause 3.2.11.…”

“…imaging technologies include Doppler ultrasound, and (contrast) angiography techniques that involve planar X-ray, MRI and CT [1] [2] [3] [4]. Analysis of physiological flows plays a fundamental role in diagnosis of numerous pathologies and for this reason it is important that flow-informed diagnosis is both sensitive and specific, based on flow-derived metrics that can reliably support clinical decision making [5] [6].…”