Biomedical subjects

Jan Gralla

Publications and source records attributed to Jan Gralla.

9 recordsLinked to original sources

PubMed2006

Mechanical thrombectomy for acute ischemic stroke: thrombus-device interaction, efficiency, and complications in vivo.

BACKGROUND AND PURPOSE: Mechanical thrombectomy is a promising new modality of interventional stroke treatment. The various devices differ with regard to where they apply force on the thrombus, taking a proximal approach such as aspiration devices or a distal approach such as basket-like devices. The study compares the in vivo effectiveness and thrombus-device interaction of these 2 approaches. METHODS: Angiography and embolization with a radioopaque whole blood thrombus was performed in 10 swine. Mechanical thrombectomy was performed in 20 cranial vessels using a proximal aspiration device (Vasco35) and a distal basket-like device (Catch) with and without proximal balloon occlusion. Fifty-six retrieval attempts were made. RESULTS: The proximal device allowed fast repeated application with a low risk of thromboembolic events (3%) and vasospasm, but it had a significantly lower success rate (39.4%) in retrieving thrombotic material than the distal device (DD) (82.6%; odds ratio, 7.3; 95% CI, 2.0 to 26.4). The compaction of the thrombus during retrieval with DD increased the risk of vessel wall irritation significantly (P<0.01) and complicated retrieval into the guiding catheter. The number of embolic events was significantly higher with DD (26%; odds ratio, 11.3; 95% CI, 1.35 to 101.6) unless proximal balloon occlusion was used. CONCLUSIONS: The proximal and the distal approaches to mechanical thrombectomy proved to be effective at achieving recanalization of cranial vessels. The proximal device is faster in application and allowed repeated attempts with a low complication rate. The DD is more successful at removing thrombotic material, but its method of application and attendant thrombus compaction increase the risk of thromboembolic events and vasospasms.

Acute Disease↗

PubMed2006

A novel multiple-trauma CT-scanning protocol using patient repositioning.

Emergency CT examination is considered to be a trade-off between a short scan time and the acceptance of artifacts. This study evaluates the influence of patient repositioning on artifacts and scan time. Eighty-three consecutive multiple-trauma patients were included in this prospective study. Patients were examined without repositioning (group 1, n=39) or with patient rotation to feet-first with arms raised for scanning the chest and abdomen/pelvis (group 2, n=44). The mean scan time was 21 min in group 1 and 25 min in group 2 (P=0.01). The mean repositioning time in group 2 was 8 min. Significantly, more artifacts were observed in group 1 (with a repeated scan in 7%) than in group 2 (P=0.0001). This novel multiple- trauma CT-scanning protocol with patient repositioning achieves a higher image quality with significantly fewer artifacts than without repositioning but increases scan time slightly.

Adolescent↗

PubMed2005

Evaluation of a 16-MDCT scanner in an emergency department: initial clinical experience and workflow analysis.

OBJECTIVE: MDCT is especially suited for emergency purposes because it allows rapid high-resolution scans of large areas, fast high-quality reformatting in every orientation, and 3D illustration of the data set. In a prospective study, we evaluated the reliability and workflow of a dedicated emergency department 16-MDCT scanner in the management of patients presenting to the emergency department. SUBJECTS AND METHODS: The use of a 16-MDCT scanner for 503 patients in the emergency department of a university clinic was evaluated. For reasons of workflow analysis, seven precise time intervals were recorded during the emergency examinations. A new setting for repositioning multiple-trauma patients after imaging of the head and neck from the head-first position to the feet-first position was introduced. RESULTS: Six (1.2%) of the 503 patients were excluded because of technical malfunction or patient noncompliance. Image quality in the remaining 497 cases, including CT angiography and CT of multiple-trauma patients, was outstanding. Positioning of the patients took from 3 to 13 min depending on the body region examined, representing 33-67% of the mean room time, which ranged from 8 to 21 min. In multiple-trauma patients, the initial positioning took a mean of 6 min and repositioning took 8 min, representing 19% and 26% of total room time, respectively. CONCLUSION: The use of a dedicated 16-MDCT scanner in the emergency department resulted in short examination times even for examinations of multiple body regions under emergency conditions. The introduced setting-repositioning of multiple-trauma patients-allowed high image quality to be maintained. The trade-off in multiple-trauma patients was prolonged room time because of patient repositioning.

Efficiency, Organizational↗

PubMed2005

High-resolution three-dimensional T2-weighted sequence for neuronavigation: a new setup and clinical trial.

OBJECT: Conventional imaging for neuronavigation is performed using high-resolution computerized tomography (CT) scanning or a T1-weighted isovoxel magnetic resonance (MR) sequence. The extension of some lesions, however, is depicted much better on T2-weighted MR images. A possible fusion process used to match low-resolution T2-weighted MR image set with a referenced CT or T1-weighted data set leads to poor resolution in the three-dimensional (3D) reconstruction and decreases accuracy, which is unacceptable for neuronavigation. The object of this work was to develop a 3D T2-weighted isovoxel sequence (3D turbo-spin echo [TSE]) for image-guided neuronavigation of the whole brain and to evaluate its clinical application. METHODS: The authors performed a phantom study and a clinical trial on a newly developed T2-weighted isovoxel sequence, 3D TSE, for image-guided neuronavigation using a common 1.5-tesla MR imager (Siemens Sonata whole-body imager). The accuracy study and intraoperative image guidance were performed with the aid of the pointer-based Medtronic Stealth Station Treon. The 3D TSE data set was easily applied to the navigational setup and demonstrated a high registration accuracy during the experimental trial and during an initial prospective clinical trial in 25 patients. The sequence displayed common disposable skin fiducial markers and provided convincing delineation of lesions that appear hyperintense on T2-weighted images such as low-grade gliomas and cavernomas in its clinical application. CONCLUSIONS: Three-dimensional TSE imaging broadens the spectrum of navigational and intraoperative data sets, especially for lesions that appear hyperintense on T2-weighted images. The accuracy of its registration is very reliable and it enables high-resolution reconstruction in any orientation, maintaining the advantages of image-guided surgery.

Adult↗

PubMed2004

New evidence for involvement of the entorhinal region in schizophrenia: a combined MRI volumetric and DTI study.

Postmortem examinations and magnetic resonance imaging (MRI) studies suggest involvement of the entorhinal cortex (EC) in schizophrenic psychoses. However, the extent and nature of the possible pathogenetical process underlying the observed alterations of this limbic key region for processing of multimodal sensory information remains unclear. Three-dimensional high-resolution MRI volumetry and evaluation of the regional diffusional anisotropy based on diffusion tensor imaging (DTI) were performed on the EC of 15 paranoid schizophrenic patients and 15 closely matched control subjects. In schizophrenic patients, EC volumes showed a slight, but not significant, decrease. However, the anisotropy values, expressed as inter-voxel coherences (COH), were found to be significantly decreased by 17.9% (right side) and 12.5% (left side), respectively, in schizophrenics. Reduction of entorhinal diffusional anisotropy can be hypothesized to be functionally related to disturbances in the perforant path, the principal efferent EC fiber tract supplying the limbic system with neuronal input from multimodal association centers. Combinations of different MRI modalities are a promising approach for the detection and characterization of subtle brain tissue alterations.

Adult↗

PubMed2004

Volumetry and diffusion tensor imaging of hippocampal subregions in schizophrenia.

Previous MRI-volumetric studies in schizophrenic psychoses have demonstrated more or less pronounced volume reductions of the hippocampus in patients. Correspondingly, neuropathological examinations on the brains of schizophrenics showed diverse structural changes of the hippocampus. Employing a high-resolution 3D-MPRAGE sequence, we found volume reductions in most hippocampal subregions of schizophrenic patients, which, however, did not reach significant levels. An analysis of co-registered diffusion tensor imaging (DTI) data revealed significant alterations of the inter-voxel coherences in single hippocampal subdivisions of these patients, supporting the assumption of characteristic microstructural tissue changes relevant for the pathogenesis of schizophrenic psychoses. Our results argue for the usage of additional MRI modalities like DTI in order to detect subtle regional alterations of hippocampal structure in schizophrenics.

Adult↗

PubMed2004

Differentiating hippocampal subregions by means of quantitative magnetization transfer and relaxometry: preliminary results.

The hippocampal formation (HF) of healthy control subjects and schizophrenic patients was examined using an MRI experiment that implements sequences for relaxometry and magnetization transfer (MT) quantification. In addition to the semi-quantitative magnetization transfer ratio (MTR), all of the observable properties of the binary spin bath model were included. The study demonstrates that, in contrast to the MTR, quantitative MT parameters (especially the T2 relaxation time of restricted protons, T2b) are capable to differentiate functionally significant subregions within the HF. The MT methodology appears to be a promising new tool for the differential microstructural evaluation of the HF in neuropsychiatric disorders accompanied by memory disturbances.

Adult↗

PubMed2004

Internal carotid artery aneurysm with life-threatening hemorrhages in a pediatric patient: endovascular treatment options.

PURPOSE: To describe the management of a pediatric patient with recurrent, life-threatening nasopharyngeal hemorrhages due to a pseudoaneurysm of the internal carotid artery (ICA), most likely caused by deep neck infection following peritonsillar abscess. CASE REPORT: An 11-year-old boy presented with lymphadenopathy of the neck, torticollis, and difficulty swallowing that had persisted for some weeks. After sneezing, the patient suffered massive recurrent nasopharyngeal hemorrhages leading to anemia. Computed tomography identified a 2 x 2-cm hematoma in the left parapharyngeal space; angiography revealed a saccular aneurysm (14.1 x 8.2 mm) of the extracranial ICA adjacent to the skull base, without ongoing hemorrhage. A bare Wallstent was initially implanted, but total exclusion was achieved only after secondary placement of a Symbiot covered stent within the bare stent. CONCLUSIONS: This case demonstrates the utility of an endovascular approach to an extracranial ICA pseudoaneurysm in a pediatric patient.

Aneurysm, False↗

PubMed2003

Intraoperative low-field magnetic resonance imaging in pediatric neurosurgery.

BACKGROUND: Since the mid-1990s, the feasibility and indications of intraoperative magnetic resonance (MR) imaging have been investigated by different groups. The majority of examinations were carried out in adults. The aim of this study was to summarize our experience of over 5 years of intraoperative MR imaging in pediatric neurosurgery. METHODS: For scanning, we used a 0.2-Tesla Magnetom Open, which was placed in a radiofrequency-shielded twin operating theater, allowing surgery with standard instruments and additional neuronavigational guidance either in an adjacent operating room or directly in the radiofrequency cabin on the extended MR table, at the 5-G line. RESULTS: In total, 330 patients were investigated, among them 33 children who were younger than 17 years. We found four main indications for intraoperative MR imaging: the evaluation of cyst drainage (n = 9), of the extent of resection in epilepsy surgery (n = 6) and of the removal of pituitary tumors (n = 6) and gliomas and other brain tumors (n = 12). Intraoperative MR imaging allowed us to evaluate the extent of the resection or to monitor catheter placements and consecutive cyst alterations in all cases. In 2 tumor cases and 3 catheter placements, intraoperative imaging resulted in a modification of the surgical strategy. CONCLUSIONS: Intraoperative low-field MR imaging is a safe procedure; we did not encounter an increased morbidity in the children investigated. It serves as intraoperative quality control documenting the effects of surgery, e.g. the extent of a resection, which can then be compared to the treatment plan. Besides its most essential application in brain tumors, it also proved to be particularly helpful in children undergoing complicated catheter placements for cyst drainage, as well as in pituitary and epilepsy surgery.

Adolescent↗