Transcranial ultrasound perfusion imaging and perfusion-MRI--a pilot study on the evaluation of cerebral perfusion in severe carotid artery stenosis

Severe internal carotid artery stenosis can cause constriction of cerebral perfusion. Different techniques of measuring brain perfusion are currently available. Ultrasound perfusion imaging (UPI) can differentiate hypoperfused and nonperfused cerebral tissue. Aim of this study was to compare the value of UPI and perfusion-weighted magnetic resonance imaging (pw-MRI) in the evaluation of cerebral perfusion in patients with severe internal carotid artery stenosis. Ten patients with severe internal carotid artery stenosis were included. UPI was performed with phase-inversion-harmonic-imaging and bolus application of contrast media for semiquantitative analysis of time-intensity curves. Time-to-peak intensity (TPI) values were compared with time-to-peak maps of pw-MRI examinations in predefined regions-of-interest (ROI). Further, a comparison of pre- and postoperative UPI data was performed in selected cases. Seven of 10 patients could be evaluated. Eighty ROIs were used for the comparison of UPI and pw-MRI, 37 ROIs were used for pre- and 36 ROIs for postoperative comparison of UPI data. There was no delay in any MRI ROI. In UPI, there were relevant delays in seven of 37 ROIs (18.9%) before and in nine of 36 ROIs (25.0%) after surgery. Eleven of these 16 ROIs (68.8%) were in the inner border zone. Compared with the established pw-MRI technique, UPI described possible subtle perfusion delays mainly of the inner border zone. These preliminary results suggest a possible diagnostic power of UPI as a noninvasive tool for the detection of hemodynamic relevance in severe internal carotid artery disease.