Judith U. Harrer

Comparative study of methods for determining vascular permeability and blood volume in human gliomas

To characterize human gliomas using T1‐weighted dynamic contrast‐enhanced MRI (DCE‐MRI), and directly compare three pharmacokinetic analysis techniques: a conventional established technique and two novel techniques that aim to reduce erroneous overestimation of the volume transfer constant between plasma and the extravascular extracellular space (EES) (Ktrans) in areas of high blood volume.

Assessment of Dural Arteriovenous Fistulae by Transcranial Color-Coded Duplex Sonography

Background and Purpose— To study hemodynamic changes and to determine the value of contrast-enhanced transcranial color-coded sonography (TCCS) for the evaluation of dural arteriovenous fistulae (DAVF) before and after transcatheter embolization. Methods— Twenty-four patients (mean age 61±11 years) with occipitally located DAVF were studied with contrast-enhanced TCCS using the transtemporal bone window in transverse-axial and coronal insonation planes. Blood flow velocity measurements of all depictable basal cerebral veins and sinuses were obtained before and after transcatheter embolization. Pretreatment and post-treatment flow velocity values were compared. Results of digital subtraction angiography (DSA) were compared with sonographic findings. Results— Four of the 24 patients (17%) could not be studied because of an insufficient temporal bone window. In all remaining patients (n=20), draining veins/sinuses could be identified because of pathologically increased blood flow velocities with peak systolic flow velocities of >50 cm/s. Of the 27 draining vessels depicted by DSA, TCCS correctly identified 25 (93%): the basal vein (3 of 3), the straight sinus (3 of 3), the superior sagittal sinus (1 of 3), the transverse sinus (9), the sigmoid sinus (4), and the superior petrosal sinus (5/5). However, TCCS failed to depict supplementary drainage via cortical veins. After transcatheter embolization, mean reduction of blood flow velocity was 44±18% (P<0.01) compared with pretreatment values. Conclusions— Contrast-enhanced TCCS is a promising technique for monitoring embolization of DAVF, follow-up after complete fistula occlusion, and may even be useful as a screening tool in patients with pulsatile tinnitus.

Extracranial and intracranial vertebral artery dissection: Long‐term clinical and duplex sonographic follow‐up

To determine the value of color Doppler sonography (CDUS) in the diagnosis and follow‐up of patients with extracranial and intracranial vertebral artery (VA) dissection.

Second Harmonic Imaging of the Human Brain: The Practicability of Coronal Insonation Planes and Alternative Perfusion Parameters

Background and Purpose— Second harmonic imaging (SHI) is a novel ultrasound technique that allows the evaluation of brain tissue perfusion. The purpose of this study was to assess normal cerebral echo contrast characteristics in 3 regions of interest (ROIs) in the transverse axial and coronal insonation planes through the temporal bone window. Materials and Methods— SHI examinations were performed in 25 patients without cerebrovascular disease (aged 50±19 years) in a transverse axial and a coronal diencephalic insonation plane through the temporal bone window. After intravenous administration of 2.5 g (400 mg/mL) of a galactose-based echo contrast agent, 62 time-triggered images with a transmission rate of 1 frame per 2.5 seconds were recorded for offline analysis. Time-intensity curves, including peak intensity (PI) (dB) and positive gradient (PG) (dB/s), were calculated to quantify ultrasound intensity in 3 different ROIs in both planes of the following sections: the thalamus (ROIthal), the lentiform nucleus (ROIncl), and the area supplied by the middle cerebral artery (ROImca). Results— Characteristic time-intensity curves with high PIs and steep PGs were recorded in each ROI. Statistical analysis of the aforementioned parameters showed no significant difference for comparison of the 3 ROIs in the transverse axial versus the coronal insonation plane. Comparison of different ROIs in the transverse axial insonation plane revealed that PI was significantly higher in ROIthal than in ROImca (7.8 versus 5.5 dB;P <0.05) and significantly higher in ROIncl than in ROIthal (9.3 versus 7.8 dB;P <0.05). In contrast, PG was comparable in ROIthal and in ROImca (0.21 versus 0.25 dB/s;P =0.42). Conclusions— SHI is a promising technique for the evaluation of cerebral parenchymal perfusion. Comparison of the transverse axial and coronal insonation planes shows similar time-intensity curves with comparable values for PIs and PGs. Coronal insonation allows the evaluation of perfusion abnormalities near the vertex and skull base, areas that cannot be depicted in the transverse axial plane. Comparison of the different ROIs indicates that the PG is a more robust and reliable parameter than the PI.

Three-Dimensional Assessment of Extracranial Doppler Sonography in Carotid Artery Stenosis Compared With Digital Subtraction Angiography

Background and Purpose— Difficulties in data presentation, data storage, and a high interobserver variability may influence color-coded Duplex sonography assessment of internal carotid artery stenosis (ICAS). The aim of our study was to evaluate the between-method agreement of ICAS using 3D color Doppler sonography (CDS) compared with digital subtraction angiography (DSA). Methods— Forty-nine patients with 64 ICASs (age 64±9 years) were involved. The patients were investigated with a color-coded duplex system using the power mode. The 3D system consists of an electromagnet that induces a low-intensity magnetic field near the patient’s head. A magnetic position sensor is attached to the probe and transmits the spatial orientation to a personal computer. Results— A total of 62 ICASs were reconstructed successfully with 3D CDS in 47 of 49 patients. High agreement for 2 independent observers was found in 3D CDS (weighted κ coefficient of 0.88). Three-dimensional CDS slightly underestimated the mean stenotic degree (mean 3D CDS 68.47±10.5 versus DSA 71.3±10.0). The intermethod agreement comparing DSA with 3D CDS was analyzed with the Bland and Altman test, which showed good agreement. Mean sensitivity of 3D CDS was 93%, mean specificity 82.5%, mean positive predictive value 82%, and mean negative predictive value 98%. Conclusions— The 3D CDS findings demonstrated good agreement compared with the gold standard, DSA, yielding higher accuracy than CDS alone. Compared with angiography or magnetic resonance angiography, 3D CDS can be performed easily on critically ill patients in stroke or intensive care units and may therefore provide a useful tool for patients unable to undergo more invasive imaging techniques.

High rate of restenosis after carotid artery stenting in patients with high-grade internal carotid artery stenosis

ObjectiveCarotid endarterectomy (CEA) is the goldstandard procedure for the majority of patients with high-grade symptomatic internal carotid artery stenosis and also for specified high-grade asymptomatic stenoses; however, a proportion of patients are treated with carotid endovascular therapy. We aimed to document medium-term clinical and neurosonographical outcome after carotid artery stenting (CAS).Methods53 patients (mean age: 65 ± 8 years) with high-grade (≥ 70 % by means of duplex sonography) carotid artery stenosis were enrolled into the study. Nineteen patients had asymptomatic, 34 patients had symptomatic stenoses. All patients had a pre-interventional CT, Doppler and duplex sonography, and digital subtraction angiography (DSA) or magnetic resonance angiography (MRA) prior to the procedural DSA. All patients were offered CEA as the gold-standard procedure and as an alternative to CAS. Both clinical and Duplex sonographical follow-up was obtained at day 1 and 7, month 1, month 3, month 6, month 12, and every subsequent 6 months after the procedure. Mean follow-up time was 22 ± 1.6 months (± SEM).Results2/53 patients suffered from stroke. A further 2 patients suffered from carotid artery occlusion shortly after CAS. The cumulative rate of restenosis during follow-up was 24.5 % (13/53). Four of these (7.5 %) were of high-grade and led to further interventional or surgical therapy.ConclusionsA high rate of restenosis was found during follow-up after CAS. Our analysis of non-selected patients emphasizes that CEA remains the gold-standard procedure for the treatment of symptomatic internal carotid artery stenosis. The frequently performed endovascular treatment of carotid stenosis outside the setting of a randomized controlled trial is not supported by our data.

Three-dimensional color-coded duplex sonography for assessment of the vertebral artery origin and vertebral artery stenoses.

Objective. The aim of the study was to assess the potential of 3‐dimensional (3D) color‐coded duplex sonography (CDS) for evaluation of the vertebral artery origin and stenoses in this location. Methods. To compare 2‐dimensional (2D) and 3D CDS, both techniques were performed in 25 healthy volunteers and in 18 patients with 21 stenoses of the vertebral artery origin. Stenoses were graded in line with hemodynamic criteria on 2D CDS and according to North American Symptomatic Carotid Endarterectomy Trial criteria on 3D CDS. In 6 patients, digital subtraction angiography (DSA) was performed additionally. Stenoses were graded according to North American Symptomatic Carotid Endarterectomy Trial criteria and compared with 2D and 3D sonographic data. Results. Overall correlation of both sonographic techniques concerning the grading of the stenoses was good (r = 0.69; P < .01). The interobserver correlation for assessment of stenoses by means of 3D CDS was high (r = 0.94; P < .01). Three‐dimensional CDS correlated excellently with DSA in 3 of 6 patients but showed only intermediate or no correlation in the remaining 3 patients. In contrast, spatial information on the stenotic morphologic characteristics was always very comparable with the results obtained by DSA. Conclusions. Three‐dimensional CDS represents a valuable tool for assessment of the origin of the vertebral artery, allowing important morphologic information on stenoses in this location. For grading of stenoses of the vertebral artery origin, 3D information should be combined with hemodynamic criteria obtained by spectral Doppler imaging in 2D CDS. Three‐dimensional CDS could be a valuable tool before interventional procedures of the proximal vertebral artery, saving time and avoiding iodinated contrast agents.

Cerebral aneurysms and arteriovenous malformations.

Cerebral aneurysms and arteriovenous malformations (AVMs), including arteriovenous fistulae, are rather seldom investigated by means of transcranial color-coded duplex sonography (TCCS). Nevertheless, the continuous improvements in high-quality scanners, ultrasound contrast enhancers, and special software, such as three-dimensional reconstruction tools, make these lesions assessable in a high number of patients. In particular, the possibility of investigating hemodynamics and hemodynamic changes in a noninvasive manner is a unique feature of TCCS, which is therefore particularly valuable for monitoring stepwise transcatheter treatment of these lesions. Limitations of the technique, mainly caused by restrictions of the insonated bone windows, render this method inadequate as a screening tool. However, TCCS has proven to be a highly useful technique for follow-up investigations of treated and untreated cerebral aneurysms and AVMs. This chapter explains the investigation of these lesions and gives an insight into the most important up-to-date literature.

MR-imaging of thrombus in extra- and intracranial arteries employing balanced fast-field echo MRI

Causes of stroke in young adults include a variety of disorders that are less frequently seen in older patients. We report the case of a young patient, who suffered recurrent mild embolic infarctions from a free-floating thrombus formation of the internal carotid artery bulb. During preoperative preparation, the thrombus dislodged and led to middle cerebral artery occlusion and major stroke. Both during preoperative work-up and after thrombus displacement balanced fast field echo sequences were able to demonstrate thrombus with a high signal-to-noise ratio and a superior delineation of thrombus and flowing blood. The high contrast between blood and thrombus helped to establish the diagnosis, to plan subsequent treatment strategies and to follow closely the clinical course. Further studies have to show whether this technique might help in thrombus characterization.

Application of Transcranial Color-Coded Duplex Sonography in Stroke Diagnosis

Cerebrovascular diagnostics are increasingly important in stroke therapy, especially in cases when the time window for IV rtPA has exceeded, in follow-up and secondary prevention of ischemic stroke. Transcranial color-coded duplex sonography (TCCS), a noninvasive and flexible method for vascular and parenchymal imaging of the adult brain, and is considered complementary to CT- and MR-Angio as the investigator depicts intracranial hemodynamics including occlusions, stenosis and the sufficiency of collateral flow. After an introduction to the general technical requirements of the ultrasound system and the defined transcranial image planes important for stroke diagnostics we focus on intracranial arterial vessel occlusions and stenosis important for cerebral ischemia work-up. UCA have had a tremendous impact on TCCS application and are used in cases of unfavorable acoustic bone windows resulting in superior signal-to-noise and yield high and fast diagnostic confidence. In addition, new developments in ultrasound signal processing and transducer technology, such as harmonic B-mode and contrast burst imaging amongst others, take advantage of microbubble specific properties which allow for increased signal retrieval as well as separation of linear and non-linear acoustic responses. Bed- side ultrasound perfusion sonography has gained special attention and first encouraging results have visualized and quan- tified perfusion defects in acute stroke patients. This review is aimed to guide the unexperienced sonographer to valid and important findings in intracranial cerebrovascular disease.