Pivotal role of multiphase computed tomography angiography for collateral assessment in patients with acute ischemic stroke

Abstract

The cerebral collateral circulation is the main compensatory mechanism that maintains the ischemic penumbra viable, the tissue at risk for infarction that can be saved if blood flow is restored by reperfusion therapies. In clinical practice, the extent of collateral vessels recruited after vessel occlusion can be easily assessed with computed tomography angiography (CTA) using two different techniques: single-phase CTA (sCTA) and multi-phase CTA (mCTA). Both these methodologies have demonstrated a high prognostic predictive value for prognosis due to the strong association between the presence of good collaterals and favorable radiological and clinical outcomes in patients with acute ischemic stroke (AIS). However, mCTA seems to be superior to sCTA in the evaluation of collaterals and a promising tool for identifying AIS patients who can benefit from reperfusion therapies. In particular, it has recently been proposed the use of mCTA eligibility criteria has been recently proposed for the selection of AIS patients suitable for endovascular treatment instead of the current accepted criteria based on CT perfusion. In this review, we analyzed the characteristics, advantages and disadvantages of sCTA and mCTA to better understand their fields of application and the potential of mCTA in becoming the method of choice to assess collateral extent in AIS patients.

Application of emerging technologies in ischemic stroke: from clinical study to basic research

“…While it is recognized that perfusion techniques such as computed tomography perfusion (CTP) can provide information on collateral circulation, they fall short in direct visualization. In contrast, CTA techniques, including single-phase CTA (sCTA) and multiphase CTA (mCTA), excel in the identification of occluded points and the visualization of collateral filling ( 33 ). mCTA includes three acquisition stages with a commendable temporal resolution, allowing a more detailed and reliable assessment of collateral vessels.…”

The Pathophysiology of Collateral Circulation in Acute Ischemic Stroke

“…Another important observation was that the tissue under severe hypoperfusion survives a shorter period of time and that the tissue in "penumbra" will inevitably progress to irreversible damage, which is to say, the "core" grows over time if perfusion is not restored [25]. What determines the survival of the penumbra is indeed the collateral circulation, but it cannot save the penumbra indefinitely [40].…”

Automated advanced imaging in acute ischemic stroke. Certainties and uncertainties

“…NCCT recognizes early ischemic changes (areas of weak parenchymal hypoattenuation such as focal hypodensity, obscuration of lentiform nucleus, loss of gray-white matter differentiation, loss of insular ribbon) corresponding to the infarct core and estimates their extent using the semiquantitative Alberta Stroke Program Early CT Score (ASPECTS) methodology but does not detect the ischemic penumbra [10] . CTA identifies the occlusion site and provides a detailed evaluation of collateral supply using two different techniques, single-phase CTA (sCTA) and multi-phase CTA (mCTA) but does not provide information about infarct core and ischemic penumbra [11] . Conversely, a recent randomized controlled trials (RCTs) showed benefit from reperfusion therapies in the late time window using advanced imaging [9] .…”