Tobias Katzer’s research while affiliated with Justus Liebig University Giessen and other places

Harmonic power-based duplex sonography is a new ultrasound method that improves the signal-to-noise ratio of extracranial vascular imaging. The authors evaluated this new method for transtemporal imaging of the basal cerebral arteries. Fundamental power-based duplex sonography (p-TCCS) and harmonic power-based duplex sonography (HI-p-TCCS) in combination with a novel perfluoropropane-containing ultrasound contrast agent (Optison) were investigated for the evaluation of the basal cerebral arteries in 12 healthy volunteers. The number of identified vascular segments and the blood flow velocities in the middle and posterior cerebral arteries were determined for p-TCCS and for two doses of Optison (0.5 and 1.5 mL) using HI-p-TCCS. Furthermore, the authors determined the time course of signal enhancement after Optison bolus injections. The results were compared using Friedman two-way ANOVA test. Significantly more arterial segments were visualized using HI-p-TCCS with enhancement of either 0.5 mL or 1.5 mL Optison (p < 0.01, each) than using p-TCCS. The spatial resolution was markedly increased with HI-p-TCCS, resulting in a striking difference in the detection of distal arterial segments and cortical and parenchymal branches. Except for the diastolic blood flow velocities (BFVs) in the M1 segment, the BFVs did not differ significantly between p-TCCS and HI-p-TCCS. Comparing HI-p-TCCS with 0.5 mL and 1.5 mL Optison, the authors found a small but significant reduction of the latency period (18.2 vs. 15.9 seconds, respectively; p < 0.01), a significant increase of the blooming phase (62.7 vs. 99.8 seconds, respectively; p < 0.0006) and a significant prolongation of the diagnostically useful signal enhancement (233.7 vs. 427.6 seconds, respectively; p < 0.004).

It is unclear which harmonic imaging mode (power Doppler or gray-scale imaging) is superior and which measuring method is the most robust for the description of brain perfusion. We performed an animal study on 6 beagles through the intact skull using a SONOS 5500 device and Optison injected intravenously in 3 different doses (0.15, 0.3, and 0.6 mL). Intensity versus heart-cycle plots for the brain parenchyma and the basal cerebral arteries were generated to evaluate the peak increase (PI) from baseline and the area under the curve (AUC). With harmonic gray-scale imaging, a homogeneous increase in echo contrast of the brain parenchyma was observed. The effect was dose dependent, resulting in a significant increase in PI as well as an insignificant increase of the AUC with 0.3 mL versus 0.15 mL contrast agent (P=0.03 and P=0.65, respectively; n=5). With harmonic power Doppler, injection of the 3 different doses resulted in a nonsignificant increase in PI and AUC P=0.17, n=6 for both). After normalization of the brain signal to the peak arterial signal in individual dogs, a significant increase could be demonstrated (P=0. 03 and P=0.01, respectively; n=6). The signal pattern of harmonic power Doppler was inhomogeneous, with stronger signal increases in the anterior part of the brain. Gray-scale imaging leads to a more homogeneous increase in echo contrast of the brain tissue and may be more suitable for displaying brain perfusion. The PI of the signal intensity seems the most robust parameter for the description of cerebral perfusion with both imaging modes under investigation.

Through harmonic gray-scale imaging, it is possible to analyze brain tissue perfusion with different ultrasound methods. In 12 healthy volunteers, 2 doses (0.5 and 1.5 mL) of Optison, a perfluoropropane-containing contrast agent, were injected intravenously and produced a strong increase of brightness in the brain parenchyma. We used harmonic imaging for quantification of ultrasound intensity in the thalamus, ipsilateral temporoparietal white matter (TPWM), and ipsilateral lateral fissure at both sides. Time-intensity curves were calculated, and peak increase (PI) of intensity and the area under the time-intensity curve (AUC) from baseline were compared. We found a significant dose dependence of the AUC in all regions at both sides. PI only showed a significant dose dependence in the TPWM but not in the ipsilateral thalamus and lateral fissure. No side differences for AUC and PI were detected in all regions and doses used. We found a significantly higher value of the PI insonating the thalamus from the ipsilateral side compared with the contralateral side. The same result was obtained for the AUC in the left thalamus for both doses and in the right thalamus for the high dose. Using 0.5 mL for insonation of the right thalamus AUC again showed a higher value for the insonation from the ipsilateral compared with the contralateral side but failed to show statistical significance (P=0.08, n=12). Harmonic gray-scale imaging with Optison showed a strong enhancement effect in the brain parenchyma. A quantitative analysis of perfusion seems difficult because of the depth dependence of the effect. The most robust parameter is the AUC.