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Hypoattenuation on CTA images with large vessel occlusion: timing affects conspicuity
Prasham Dave1, Cheemun Lum2,3, Rebecca Thornhill2,3
1MD Program, Faculty of Medicine, University of Ottawa, Roger Guindon Hall, 451 Smyth Road, Room 2046, Ottawa, K1H 8MH, ON, Canada. Prasham.Dave@UOttawa.ca.
Neuroradiology
|April 2, 2017
Summary
Contrast timing significantly impacts the visibility of ischemic areas on CT angiography source images (CTASI) in acute stroke. Optimal detection of brain tissue damage occurs during the mid-phase of the time-attenuation curve.
Area of Science:
- Neuroradiology
- Acute Stroke Imaging
- Cerebrovascular Imaging
Background:
- Parenchymal hypoattenuation on CT angiography source images (CTASI) indicates ischemic tissue.
- The conspicuity of these ischemic areas varies with contrast material transit.
- Objective measurement of this conspicuity is crucial for stroke assessment.
Purpose of the Study:
- To evaluate how contrast timing affects the conspicuity of ischemic brain tissue on CTASI.
- To determine the optimal phase for visualizing hypoattenuation distal to large vessel occlusions.
Main Methods:
- Retrospective analysis of patients with large vessel occlusions undergoing dynamic multiphase CT angiography (CTA) and CT perfusion (CTP).
- Identification of ischemic regions using low cerebral blood volume on CTP.
- Region of interest (ROI) placement in ischemic and normal tissue on CTASI to compare attenuation over time.
Main Results:
- Conspicuity of ischemic areas was significantly influenced by the phase of contrast arrival (P < 0.00001).
- Median absolute and relative conspicuity were highest during the peak arterial, notch, and peak venous phases.
- Objective conspicuity measurements demonstrated a clear dependence on the time-attenuation curve (TAC).
Conclusions:
- The conspicuity of ischemic areas in acute stroke is phase-dependent on dynamic CTASI.
- Mid-phase contrast arrival on the TAC offers the greatest objective conspicuity for ischemic tissue.
- Dynamic CTASI analysis can objectively quantify the visibility of ischemic changes in acute stroke.
