We read the article by Byrne et al, “Improved Detection of Anterior Circulation Occlusions: The ‘Delayed Vessel Sign’ on Multiphase CT Angiography” with great interest. However, we would like to point out other important aspects of multiphase CT angiography (mCTA) to the readers of the Multiphase CTA is a useful recent addition to neurovascular imaging in acute stroke, providing information on the degree and extent of pial arterial filling in the whole brain in a time-resolved manner. It was designed to assess pial vessel asymmetry in terms of delayed contrast filling and/or delayed contrast washout compared with the contralateral side. The time-resolved imaging acquisition additionally enables judgment on either antegrade or retrograde pial vessel contrast filling and thus gives the reader information on clot permeability, collateral circulation, and possible response to thrombolytic therapy.
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