Detection of Perfusion Deficits in Multiphase Computed Tomography Angiography—A Stroke Imaging Technique Based on Iodine Mapping on Spectral Computed Tomography: Initial Findings

Objective: The purpose of this study was to explore a novel method for
brain tissue differentiation using quantitative analysis of multiphase computed
tomography (CT) angiography (MP-CTA) on spectral CT, to assess
whether it can distinguish underperfused fromnormal tissue, using CT perfusion
(CTP) as reference.
Methods: Noncontrast CT and MP-CTA images from 10 patients were
analyzed in vascular regions through measurements of Hounsfield unit (HU)
at 120 kV, HU at 40 keV, and iodine density. Regions were categorized
as normal or ischemic according to CTP. Hounsfield unit and iodine
density were compared regarding ability to separate normal and ischemic
tissue, the difference in maximum time derivative of the right over
left hemisphere ratio.
Results: Iodine density had the highest maximum time derivatives and
generated the largest mean separation between normal and ischemic tissue.
Conclusions: The method can be used to categorize tissue as normal or
underperfused. Using iodine quantification seems to give a more distinct
differentiation of perfusion defects compared with conventional HU.