Andre Kemmling MD, Presenter: Nothing to Disclose

Shervin Kamalian MD, Abstract Co-Author: Nothing to Disclose

Rainer Krumm, Abstract Co-Author: Nothing to Disclose

Shahmir Kamalian MD, Abstract Co-Author: Nothing to Disclose

Michael H. Lev MD, Abstract Co-Author: Consultant, General Electric Company Consultant, Takeda Pharmaceutical Company Limited Research support, General Electric Company Stockholder, General Electric Company

CT-perfusion (CTP) is frequently used in acute stroke imaging, however, there is need for further standardization for reliable quantification of tissue at risk. Using a global threshold to predict infarct is not precise. Vascular status, in particular proximal branch occlusion, is an important predictor for outcome. The purpose was to present a holistic stroke imaging approach by combining CTP maps with a priori infarct probability defined by site of vessel occlusion to improve prediction of infarct.

A novel method is presented to derive CTP based images displaying voxel-wise probability of infarction: 1) In 83 MCA occlusive stroke, voxel-wise sensitivity and specificity for infarction for incremental perfusion thresholds was measured with respect to tissue-outcome lesion maps at 48h. CT perfusion parameters (gray value at any voxel) in CTP images were converted to likelihood ratios defined by sensitivity/(1-specificity). Thus, the discriminative power for every perfusion value with respect to tissue outcome was directly encoded within the perfusion image. 2) A probabilistic a priori map in standard space based on 103 non-recanalized distal M1-MCA occlusive strokes at 48h after onset was generated. Lesion-masks were registered to standard MNI-152 space. 3) The pre-test probability map for M1-occlusive strokes was transformed to CTP space and multiplied by the CTP based likelihood ratio to obtain a post-test map displaying voxel-wise probability of infarction.

In 10 sample cases, infarct probability in admission imaging was displayed and compared to follow up imaging at 48h. Areas of >95% infarct probability correlated very well with actual tissue outcome. In contrast to original CTP maps, the resulting probability map exclusively displays voxels at risk of infarction. Noise was significantly reduced.

Infarct prediction can be improved combining CT perfusion maps with a priori infarct probability defined by site of vessel occlusion. Further studies are warranted.

Standardization of multi-modal stroke imaging is crucial for clinical applicability. The presented method combines site of vessel occlusion and CT perfusion imaging for improved infarct prediction.

Kemmling, A, Kamalian, S, Krumm, R, Kamalian, S, Lev, M, Improved Prediction of Tissue Outcome after Acute Ischemic Stroke: A Priori Infarct Probability Defined by Site of Vessel Occlusion Can Be Combined with Infarct Likelihood-Ratios Based on CT Perfusion Imaging.  Radiological Society of North America 2012 Scientific Assembly and Annual Meeting, November 25 - November 30, 2012 ,Chicago IL. http://archive.rsna.org/2012/12043747.html