Parametric Perfusion Imaging With Contrast-Enhanced Ultrasound in Acute Ischemic Stroke

Abstract

Background and Purpose-Color-coded perfusion maps can be calculated from ultrasound harmonic gray-scale imaging data after ultrasound contrast agent bolus injection to analyze brain tissue perfusion. First reports indicate that this method can display cerebral perfusion deficits in acute ischemic stroke. We performed a prospective patient study to evaluate this approach. Methods-Thirty consecutive patients suffering from acute middle cerebral artery infarction who presented to our department within 12 hours after symptom onset were investigated with ultrasound perfusion harmonic imaging (PHI) after Levovist bolus injection. Color-coded perfusion maps were calculated from the ultrasound data. In addition, the original gray-scale images were analyzed in cine mode. Findings were compared with those of cranial CT. Results-All 30 patients suffered from acute ischemic stroke of the middle cerebral artery territory (median National Institutes of Health Stroke Scale score, 16 points). Twenty-three of the 30 patients (76.7%) had sufficient PHI insonation conditions. In 19 of these 23 patients (82.6%), a marked deficit in contrast enhancement could be visualized by initial PHI with the color-coded parameter images and cine-mode images. In 17 of the 23 (73.9%), the perfusion deficit was found on the parameter images. The area of hypoperfusion in the initial PHI investigation corresponded to the definite area of infarction in follow-up cranial CT. In 3 of 23 patients (13.0%), a perfusion deficit could be demonstrated in PHI, although the supplying artery was found patent by transcranial color-coded duplex sonography. Conclusions-With PHI, it is possible to display cerebral perfusion deficits in acute ischemic stroke. PHI yields additional information on the perfusion state of the human brain compared with extracranial and transcranial color-coded duplex sonography.

Update on Ultrasound Techniques for the Diagnosis of Cerebral Ischemia

“…Many studies have demonstrated the value of UPI for the depiction of blood flow in the microcirculation of the brain in healthy animals [82,83] and humans [84]. Furthermore, there is mounting evidence that echo contrast harmonic imaging can be used to visualize perfusion deficits in patients with acute stroke, although the studies have used different harmonic imaging modalities [11, 85, 86]. …”

Ultrasound Contrast Agents in Ischemic Stroke

“…5) such as the time to peak intensity (TPI), the peak intensity (PI), the mean transit time, the peak width (full width at 90% of the maximum intensity and full width at half the maximum intensity), the area under the curve, the positive gradient (defined as PI/TPI), and the peak signal increase. These parameters can then be displayed as parametric images [52]. …”

“…Several studies have shown that such parameters may be suitable for assessment of the perfusion state, particularly the analysis of local time-intensity curves in prespecified ROI [37] or the visual interpretation of parametric images [52,53,54,55,56]. MRI and PET studies in acute stroke patients have demonstrated the diagnostic value of TPIs maps for differentiation between unaffected parenchyma, penumbra, and ischemic core area [57].…”

Contrast-Enhanced Ultrasound Perfusion Imaging in Acute Stroke Patients

“…2) such as time-to-peak intensity (TPI), peak intensity (PI), mean transit time, peak width (full width at 90% of the maximum intensity and full width at half the maximum intensity), area under the curve, positive gradient (defined as peak intensity/TPI), and peak signal increase. These parameters can then be displayed as parametric images [15]. …”

“…Several studies have shown that such parameters may be suitable for assessment of the perfusion state, particularly the analysis of local time-intensity curves in prespecified regions of interest [5] or the visual interpretation of parametric images [15,16,17,18,19]. MRI and PET studies in acute stroke patients have demonstrated the diagnostic value of TPI maps for differentiation between unaffected parenchyma, penumbra, and ischemic core area [20].…”