Improved dynamic CT angiography visualization by flow territory masking
Søren Christensen1, Bruce Campbell2, Maarten G Lansberg3, Jacqui Hislop-Jambrich4, Stephen Davis2, Patricia Desmond1, Mark Parsons5
1 Department of Radiology, University of Melbourne, Melbourne, Victoria, Australia
2 Department of Neurology, University of Melbourne, Melbourne, Victoria, Australia
3 Department of Neurology, Stanford Stroke Center, Stanford University, California, USA
4 Clinical Applications Research Centre, North Ryde, Sydney, New South Wales, Australia
5 Department of Neurology, Hunter Medical Research Institute, John Hunter Hospital, University of Newcastle, Newcastle, New South Wales, Australia
Stanford Stroke Center, 780 Welch Road, Suite 350, Stanford, California - 94305
Source of Support: None, Conflict of Interest: None
Backgound and Purpose: Computerized tomography (CT) perfusion (or CTP) source images from CT scanners with small detector widths can be used to create a dynamic CT angiogram (CTA) similar to digital subtraction angiography (DSA). Because CTP studies use a single intravenous injection, all arterial territories enhance simultaneously, and individual arterial territories [i.e., anterior cerebral artery (ACA), middle cerebral artery (MCA), and posterior cerebral artery (PCA)] cannot be delineated. This limits the ability to assess collateral flow patterns on dynamic CTAs. The aim of this study was to devise and test a postprocessing method to selectively color-label the major arterial territories on dynamic CTA.
Materials and Methods: We identified 22 acute-stroke patients who underwent CTP on a 320-slice CT scanner within 6 h from symptom onset. For each case, two investigators independently generated an arterial territory map from CTP bolus arrival maps using a semiautomated method. The volumes of the arterial territories were calculated for each map and the average relative difference between these volumes was calculated for each case as a measure of interrater agreement. Arterial territory maps were superimposed on the dynamic CTA to create a vessel-selective dynamic CTA with color-coding of the main arterial territories. Two experts rated the arterial territory maps and the color-coded CTAs for consistency with expected arterial territories on a 3-point scale (excellent, moderate, poor).
Results: Arterial territory maps were generated for all 22 patients. The median difference in arterial territory volumes between investigators was 2.2% [interquartile range (IQR) 0.6-8.5%]. Based on expert review, the arterial territory maps and the vessel-selective dynamic CTAs showed excellent consistency with the expected arterial territories in 18 of 22 patients, moderate consistency in 2 patients, and poor consistency in another 2 patients.
Conclusion: Using a novel postprocessing technique, arterial territory maps and dynamic CTAs with vessel-selective color-coding can be derived from a standard CTP scan. These maps may be used to noninvasively assess collateral flow in patients with acute stroke.