In Vivo Assessment of the Impact of Regional Intracranial Atherosclerotic Lesions on Brain Arterial 3D Hemodynamics

Abstract

Regional intracranial atherosclerotic lesions not only alter distal arterial flow but also significantly affect ipsilateral collateral arterial hemodynamics.

Semi‐automated analysis of 4D flow MRI to assess the hemodynamic impact of intracranial atherosclerotic disease

“…Ruland et al reported possible PCA‐to‐MCA collateral flow pathway in stenotic MCA patients. Wu et al also proposed PCA compensation in addition to increased blood flow in the ipsilateral ACA in patients with MCA stenosis, which was in agreement with findings of Brass et al We observed similar changes in a number of ICAD patients. However, the comparison of FR and PV between ipsilateral and contralateral vessels may be unreliable because of anatomic variations in the CoW .…”

“…For instance, there was an outlier in the moderate subgroup (Figure A, PD of 3.79 mm Hg and hemisphere PV ratio of 2.56), where the blood flow redistibution may be influenced by 2 opposing phenomena. The subject presented with an aplastic A1 segment of the contralateral ACA, a normal CoW anatomic variant, resulting in increased blood flow to ipsilateral ICA and ACA, as opposed to the stenotic MCA effect that is associated with blood flow reduction in ipsilateral ICA . Therefore, in this patient, the FR and PV of ipsilateral ICA increased instead of decreasing.…”

“…In this retrospective study, we used a preset high‐venc of 120 cm/s because 4D flow MRI was part of a clinical protocol. From our experience with previous 4D flow MRI studies in patients with ICAD, we learned that maximum velocity in the stenosis would hardly exceed 120 cm/s. This setting was suitable for majority of cases with 1 exception that was excluded.…”

“…To better assess ICAD, local flow rate and velocity across the stenosis and distal vasculature have been evaluated as biomarkers for recurrent stroke . Additionally, it has been shown that intracranial stenosis can globally influence blood flow across the cerebrovascular network . Pressure drop across the lesion has been proposed for assessing stroke risk .…”

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

“…In a preliminary study, Hope et al (21) suggested time-of-flight MRA to be inferior to 4D flow MRI in the hemodynamic assessment of patients with intracranial atherosclerotic disease. In a separate study, 4D flow MRI characterized asymmetric flow indices in patients with intracranial atherosclerotic disease compared to age-appropriate controls (67), influencing both distal and ipsilateral collateral arterial hemodynamics. Quantitative hemodynamic data using 4D flow MRI may provide additional insight into the pathophysiology and risk stratification of intra-/extra-cranial atherosclerotic disease based on tissue susceptibility to low flow states or poor augmentation of collateral flow.…”