Monitoring of brain tissue perfusion utilizing a transducer holder for transcranial color duplex sonography.

OBJECTIVE: We have improved a transducer holder for transcranial color duplex sonography (TCDS) monitoring via both the temporal and foraminal windows (TW/FW). The objective is to clarify the clinical usefulness of and identify problems with TCDS monitoring in the evaluation of brain tissue perfusion. METHODS: Brain tissue perfusion was monitored in 11 patients (ages 31-94, mean 66). After an intravenous bolus, power modulation imaging (PMI) in all cases and second harmonic imaging (SHI) in two cases were evaluated at the diencephalic horizontal plain via bilateral (6 cases) and unilateral (5 cases) TWs. After a transducer was installed into the holder, acetazolamide (ACZ) cerebral vasoreactivity utilizing PMI was evaluated in ten cases. RESULTS: PMI proved superior to SHI in the quantitative evaluation of the bilateral hemispheres via the unilateral TWs. Brain tissue perfusion could be precisely quantified before/after ACZ in the same regions of interest (ROI). All patients could be monitored continuously by one examiner. Fixed-probe shifts during monitoring were easily readjustable. Owing to re-fixation for contra-lateral TW monitoring, it was not possible to evaluate precisely in the same ROIs. CONCLUSION: TCDS monitoring succeeds in continuously and quantitatively evaluating precise and reproducible intracranial hemodynamics in the brain tissue.

Grading carotid stenosis using ultrasonic methods.

The controversy as to whether Doppler ultrasonic methods should play a role in clinical decision-making in the prevention of stroke is attributable to reported disagreement between angiographic and ultrasonic results and the lack of internationally accepted ultrasound criteria for describing the degree of stenosis. Foremost among the explanations for both is the broad scatter of peak systolic velocities in the stenosis, the criterion that has so far received most attention. Grading based on a set of main and additional criteria can overcome diagnostic errors. Morphological measurements (B-mode images and color flow imaging) are the main criteria for low and moderate degrees of stenosis. Increased velocities in the stenosis indicate narrowing, but the appearance of collateral flow and decreased poststenotic flow velocity prove a high degree stenosis (≥70%), additionally allowing the estimation of the hemodynamic effect in the category of high-degree stenosis. Additional criteria refer to the effect of a stenosis on prestenotic flow (common carotid artery), the extent of poststenotic flow disturbances, and derived velocity criteria (diastolic peak velocity and the carotid ratio). This multiparametric approach is intended to increase the reliability and the standard of reporting of ultrasonic results for arteriosclerotic disease of the carotid artery.

Comparison of transcranial brain tissue perfusion images between ultraharmonic, second harmonic, and power harmonic imaging.

BACKGROUND AND PURPOSE: To clarify optimal brain tissue perfusion images visualized by transcranial ultrasound harmonic imaging, we compared gray-scale integrated backscatter (IBS) images of new ultraharmonic imaging (UHI) and conventional second harmonic imaging (SHI) with power harmonic imaging (PHI) (harmonic B-mode with harmonic power Doppler images) in 10 patients with and 4 without a temporal skull. METHODS: Using a SONOS 5500 (Philips), we evaluated transient response images taken after a bolus Levovist injection at a horizontal diencephalic plane via temporal windows. Based on transmitting/receiving frequencies (MHz), 4 imaging procedures using an S3 transducer (SHI2.6 [1.3/2.6], UHI [1.3/3.6], PHI2.6 [1.3/2.6], and PHI3.2 [1.6/3.2]) and 2 imaging procedures using an S4 transducer (SHI3.6 [1.8/3.6] and PHI3.6 [1.8/3.6]) were compared in terms of size and location, peak intensity (PI), contrast area demarcation, and background image quality. RESULTS: In intact skull cases, gray-scale imaging tended to show larger contrast areas than PHI. A large contrast area was most frequently observed in SHI2.6 images, despite there being more high-PI cases in UHI. No contrast area with unclear background was observed in a few cases. In craniectomized cases, all contrast images tended to have large and high PI compared with the intact skull cases. PHI, particularly PHI3.6, demonstrated sharper demarcation and a clearer background than gray-scale imaging. CONCLUSIONS: Transcranial gray-scale SHI using a low receiving frequency of 2.6 MHz is the superior method. PHI identifies contrast area localization better than gray-scale imaging and is particularly suitable for intraoperative and postoperative cases.