On the ability of ultrasound parametric perfusion imaging to predict the area of infarction in acute ischemic stroke

Purpose: Cerebral perfusion deficits in acute ischemic stroke can be detected by means of transcranial harmonic imaging after ultrasound contrast agent bolus injection. We evaluated five different parameters of the bolus kinetics as parametric images and correlated areas of disturbed perfusion with the area of definite infarction. Materials and Methods: Perfusion harmonic imaging after SonoVue® bolus injection (BHI) was used to investigate 22 patients suffering from acute internal carotid artery infarction. For each subject, we calculated five different images based on the following parameters from the time-intensity curve in each pixel: pixelwise peak intensity (PPI), area under the curve (AUC), positive gradient (PG), time to peak (TTP), and a three factor image from the factor analysis of medical image sequences (FAMIS). The findings in the diencephalic imaging plane were compared with the definite area of infarction, as diagnosed by cranial CT. Results: In predicting the definite area of infarction in follow-up CT, we found the following sensitivities and positive predictive values (PPV): PPI (100%/95%), AUC (100%/90%), FAMIS (89%/89%), PG (84%/94%) and TTP (47%/100%). The areas of disturbed perfusion in all five types of parametric images correlated significantly with the area of infarction in CT. Images from the FAMIS algorithm and PPI images showed the highest Spearman rank correlation with the area of definite infarction as displayed in CT (both r = 0.76, p < 0.001). Images from the other parameters correlated as follows: PG: r = 0.62 (p = 0.003), AUC: r = 0.53 (p = 0.014), TTP: r = 0.50 (p = 0.021). Conclusion: BHI can detect disturbed perfusion in acute hemispheric stroke. In their ability to predict the development of an infarction, intensity-based parameters and FAMIS were determined to have a high sensitivity, and TTP was found to have a high PPV and specificity.