Abstract
Various imaging protocols exist for the identification of vessel occlusion and assessment of collateral flow in acute stroke. CT perfusion is particularly popular because the color maps are a striking visual indicator of pathology. Multiphase CTA has similar diagnostic and prognostic ability but requires more expertise to interpret. This article presents a new multiphase CTA display format that incorporates vascular information from all phases of the multiphase CTA series in a single time-variant color map, thereby facilitating multiphase CTA interpretation, particularly for less experienced readers. Exemplary cases of multiphase CTA from this new display format are compared with conventional multiphase CTA, CT perfusion, and follow-up imaging to demonstrate how time-variant multiphase CTA color maps facilitate assessment of collateral flow, detection of distal and multiple intracranial occlusions, differentiation of pseudo-occlusion from real occlusion, and assessment of flow relevance of stenoses, ante- and retrograde flow patterns, and clot permeability.
Highlights
Multiphase CTA provides time-resolved images of the cerebral vasculature that satisfy many of the above requirements for use in patients with acute stroke
Good collaterals as determined on CTA have been shown to blood flow but with more complex acquisition and postprocessing, is considered easier to interpret because the display format is a single color-coded cerebral map of estimated blood flow and predicted tissue fate. This feature is in spite of obvious disadvantages of CTP, including longer image-acquisition times, susceptibility to patient motion, more radiation exposure, an additional contrast dose, a lack of whole-brain coverage, and complex and heterogeneous postprocessing algorithms. Multiphase CTA (mCTA), on the other hand, requires no postprocessing, has a lower radiation dose, and can be acquired in,30 seconds, thereby minimizing motion artifacts. In this primarily descriptive article, we present the case for a novel mCTA display format that encodes vascular information from all mCTA phases into a single color-coded map using a simple algorithm, thereby combining the indicator effect of color with the technical advantages of mCTA
Pial artery filling and collateral flow are relatively easy to assess on conventional mCTA, the color-coded summation maps (ColorViz) further facilitate interpretation by combining all information into a single image and using a color-coded display format
Summary
Multiphase CTA (mCTA) provides time-resolved images of the cerebral vasculature that satisfy many of the above requirements for use in patients with acute stroke. Color-coded correlate with reduced infarct volume in patients presenting beyond 6 hours.[1] Most interesting, no association between collateral status and outcome was noted in this study.[1] CTP, another mCTA summation maps presented here were created on a workstation using the FastStroke research prototype (GE Healthcare, Milwaukee, Wisconsin), a CT image-analysis software package imaging technique with time-resolved images of parenchymal that is intended to display the full set of imaging information of AJNR Am J Neuroradiol 41:200–05 Feb 2020 www.ajnr.org 201
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