Showing papers by "Johannes Slotboom published in 2008"

Mechanical thromboembolectomy for acute ischemic stroke: comparison of the catch thrombectomy device and the Merci Retriever in vivo.

Abstract: Background and Purpose— The purpose of the study was to compare efficacy and potential complications of 2 commercially available devices for mechanical thromboembolectomy. Methods— Devices were tested in an established animal model allowing the use of routine angiography catheters and thrombectomy devices. Radio-opaque thrombi were used for visualization of thrombus–device interaction during angiography. The Merci Retrieval System and the Catch Thromboembolectomy System were assessed each in 10 vessel occlusions. For every occluded vessel up to 5 retrieval attempts were performed. Results— Sufficient recanalization was achieved with the Merci Retriever in 90% of occlusions, and with the Catch device recanalization was achieved in 70% of occlusions. Recanalization at the first attempt occurred significantly more often with the Merci Retriever compared to the Catch device (OR, 21; 95% CI, 1.78–248.11). Consequently, significantly more attempts (P=0.02) had to be performed with the Catch device; therefore, t...

Occlusion length is a crucial determinant of efficiency and complication rate in thrombectomy for acute ischemic stroke.

Abstract: BACKGROUND AND PURPOSE: Although mechanical thrombectomy (MT) has an encouragingly high recanalization rate in treating stroke, it is associated with severe complications of which the underlying factors have yet to be identified. Because MT is a mechanical approach, the mechanical properties of the thrombus might be crucial for its success. The present study assesses the effect of thrombus length on the in vivo effectiveness and complication rate of MT. MATERIALS AND METHODS: Angiography and embolization of 21 cranial vessels with radiopaque whole-blood thrombi 10, 20, and 40 mm in length (7 occlusions each) were performed in 7 swine. MT was carried out using a distal snarelike device (BCR Roadsaver) with proximal balloon occlusion. A total of 61 retrievals were attempted. RESULTS: In the group of 10-mm occlusions, 77.8% of the attempts achieved complete recanalisation. For longer occlusions, the success rates decreased significantly to 20% of attempts for 20-mm occlusions (odds ratio [OR], 14; 95% confidence interval [CI], 2.2–89.2) and 11.1% for 40-mm occlusions (OR, 28; 95% CI, 3.9–202.2; P CONCLUSIONS: MT using a distal device proved to be a fast, effective, and safe procedure for recanalizing short (10-mm) occlusions in the animal model. However, occlusion length emerged as a crucial determinant for MT with a significant decrease in recanalization success per attempt and increased complication rates. These findings suggest limitations of MT in the clinical application.

A novel method for analyzing DSCE-images with an application to tumor grading.

Abstract: Objectives: (a) The development of a novel analysis method, named Dynamic pixel intensity Histogram Analysis (DHA) allowing for pixel intensity-histogram-model-parameter fitting of arbitrary-shaped regions defined in dynamic-susceptibility-contrast-enhanced (DSCE) difference MR-image time-series, and (b) its prospective application and evaluation for glioma grading. Materials and Methods: For each difference-image, pixel intensity histograms of arbitrary-shaped ROIs were computed and fitted using the Levenberg-Marquardt algorithm. Time-dependent histogram center-position- and width-parameters are computed during bolus-passage. The method was applied to 25 patients with low and high grade gliomas. Results: During bolus outflow-time, histogram-center-position-parameter and histogram-width-parameter reach highest significance levels and discriminate gliomas of different grades. The histogram center-position-parameter discriminated grade-II from grade-III, grade-II from grade-IV but not grade-III from grade-IV. The observed histogram width-parameters discriminated grade-II from grade-III (P < 0.00022), grade-II from grade-IV (P <8.3 10- 7 ), and grade-III from grade-IV (P < 0.00063). Conclusions: DHA is a easy-to-use method for glioma grading; the histogram width parameter is best indicator for histologic grade.

Vascular Dynamics of Cerebral Gliomas Investigated with Selective Catheter Angiography, Perfusion CT and MRI

Abstract: To assess if intratumoral blood circulation parameters from dynamic susceptibility contrast (DSC) MRI and dynamic CT deliver comparable results and to compare tumor-related changes in regional cerebral blood flow (rCBF) and regional cerebral blood volume (rCBV) with arterial, intratumoral, and venous transition detected with digital subtraction angiography (DSA). Ten patients with cerebral gliomas were prospectively studied with DSC-MRI, dynamic CT and DSA. Tumor areas were segmented and perfusion maps for rCBF, rCBV, and mean transit time (MTT) were computed from DSC-MRI and dynamic CT. Arterial circulation time (ACT), intermediate circulation time (ICT), and venous appearance time (VAT) were measured with DSA. Asymmetry indices (AIs) were calculated for MRI- and CT-based perfusion values, for ICT and VAT and compared among each other. DSC-MRI and dynamic CT yielded comparable AI values for rCBF (MRI: 39.5 ± 20.4, CT: 36.0 ± 17.9, Pearson's correlation r2 = 0.91) and rCBV (MRI: 44.6 ± 20.9 vs. CT: 40.9 ± 16.3, r2 = 0.84). The MTT AI (MRI: –4.7 ± 11.2 vs. CT: –0.5 ± 10.4, r2 = 0.47) showed only a weak correlation. ICT correlated with rCBV (ICT: 38.4 ± 14.7, r2 = 0.59, and dynamic CT: r2 = 0.81) and VAT with rCBF (VAT: 31.7 ± 17.6, r2 = 0.73, and dynamic CT: r2 = 0.87), but not with MTT. CT and MRI methods provide consistent information about tumor vascularity of cerebral gliomas in accordance with DSA.

Response to Letter by Yousaf et al

Abstract: Response: We deeply appreciate the interest of Dr Yousaf and his colleagues in our study and we understand their concerns. Certainly, differences in vessel characteristics exist between species and vascular territories, especially when compared to human brain vessels. Therefore, care must be taken when comparing complication rates assessed by animal models to complication rates in humans. However, we encounter a large variety of vessel conditions even in humans during our daily work: from young and straight vessels to elongated, sclerotic and dilated vessels, from vessels prone to spasm (more often found in younger patients) to less reactive arteries.1,2 These different vessel …

Reliability testing of in vivo 1 H-MRS-signals and elimination of signal artifacts by median filtering

Abstract: In order to make SV-MRS clinically viable, assessment of spectral quality and reliability of the data should preferably be handled by the MR-scanner system rather than by medical staff. The reliability of the data is most affected by patient motion during acquisition. In this paper, we devise, apply, and test two statistical methods that can be used for automated data reliability- and quality-assessment. Next, we establish that, in order to assess the reliability of SV-MR-data, it is essential to store the data of each acquisition separately, rather than averaging the data of all acquisitions irreversibly prior to storage. We propose a) statistical tests on these separately stored acquisitions that can reveal artifacts, b) application of a special type of order-statistics filtering, namely median filtering, once artifacts have been detected. Furthermore, we develop computer algorithms that provide automated, fully user-independent information on spectral quality and reliability of the acquired spectra. Finally, we conclude that combination of statistical tests with median filtering can provide user-free quality and reliability assessment and improvement of SV-MR-spectra.