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Biomedical subjects

J Bernarding

Publications and source records attributed to J Bernarding.

At least 19 recordsLinked to original sources
PubMed2007

[Validity of a web-based color vision test for screening examinations of color vision].

BACKGROUND: With standardized examination conditions, a web-based color vision test using pseudoisochromatic color plates can deliver test results comparable to those yielded by conventional color vision tests. The aim of the study is to analyze to what extent a web-based color vision test can be used as a screening test on the internet after visual monitor calibration. METHODS: A German-language web-based color vision test with 25 pseudoisochromatic color plates based on the color plates of Velhagen and Broschmann and of Ishihara was developed, which can be seen at http://www.farbsehtest.de. Volunteers were recruited by means of specific information distributed on the internet, in various print media, and on the radio. RESULTS: Over a period of 12 months, 2,126 of the initial volunteers [541 women and 1,588 men; mean age 34.27 (+/-14.1) years] with a valid test result for 25 color plates performed the web-based color vision test, 1,700 (506 women and 1,194 men) of whom passed it. Of the 426 volunteers who did not pass the test, 32 were women and 394, men. Counter-testing was performed on 101 volunteers (34 women and 67 men) with a mean age of 36.74 (+/-11.6) years. CONCLUSIONS: The results recorded in the patients who underwent counter-testing suggest that, if handled correctly, the web-based color vision test can be used as a color vision screening test on the internet.

Adolescent↗
PubMed2006

[Virtual microscopy and digital pathology].

Virtual microscopy has advanced considerably and is bound to be integrated into routine diagnostics in the very near future. Its integration into existing information systems builds up digital pathology. In this review, we present details, advantages and limitations of this novel technology and describe solutions regarding its adaptation to routine workflow. The chief aim is to define an uniform data format for virtual specimens to guarantee an interoperability between different systems. In the long term, digital archives and networks will be established that will allow for a worldwide access to virtual specimens.

Humans↗
PubMed2004

In vivo 1H magnetic resonance spectroscopy of rat brain after valproate administration.

Previous studies have shown that valproate is detectable in vitro by 1H magnetic resonance spectroscopy (MRS) at 1.5 T, whereas in patients on valproate monotherapy, no significant dose-dependent valproate signal could be seen. To investigate whether an increased signal-to-noise ratio as provided by higher valproate doses and increased magnetic field strength would enable detection of valproate in vivo, six Wistar rats were examined using volume-selective 1H MRS at 2.34 T. The spectra were analyzed by fitting a linear superposition of the basis spectra of valproate, brain metabolites, and simulated lipid signals. The analysis revealed no significant signal contributions after valproate administration of up to 330 mg/kg body weight. To analyze how underlying mechanisms, such as potential drug interactions with macromolecules, may affect the valproate signal, additional in vitro spectra of valproate were measured before and after adding albumin. The spectra exhibited a strong decrease of the valproate signal with increasing albumin concentration. The results support the hypothesis that in vivo valproate is bound to a high degree to macromolecules and will therefore not be detectable by 1H MRS.

Animals↗
PubMed2003

Navigated diffusion-weighted imaging with interpolated phase-correction for high-resolution imaging of stroke.

Stroke imaging was revolutionised with the introduction of diffusion-weighted MRI (DWI). The commonly used echoplanar DWI suffers from geometrical distortion near the skull base and the frontal regions and from reduced spatial resolution and fat suppression. To allow a voxel-by-voxel comparison between high-resolution spin-echo images, we implemented spin-echo-based DWI. Motion artefacts were eliminated by phase correction in hybrid frequency-Fourier domain using navigator echoes. In a novel approach, distorted navigator echoes which did not eliminate motion artefacts were replaced with interpolated navigator echoes, leading to restored image information. Navigated DWI yielded high-resolution images in 21 of 24 patients with brain ischaemia, allowing diagnosis of even small or diffuse zones of ischaemia. We determined the spatial distribution and mean of T(2)- and DWI signal intensity and apparent diffusion coefficients (ADC), using a multidimensional histogram-based analysis. Mean ADC were decreased in ischaemic areas less than 9 days old. The technique may also be useful for high-resolution DWI of tissue other than the brain.

Aged↗
PubMed2003

Volume-selective 1H MR spectroscopy for in vivo detection of valproate in patients with epilepsy.

We performed volume-selective 1H MR spectroscopy (1H-MRS) on 12 patients on valproate monotherapy to detect valproate in vivo in the brain. We also acquired reference valproate spectra in vitro in subphysiological 15 g/l albumin solution in saline, in which valproate showed two resonance peaks at 0.7 and 1.2 ppm and a minimum detection threshold of 240 mg/l. In vivo 1H-MRS spectra in brain showed peaks between 0.6 and 1.6 ppm. Simultaneous serum valproate concentrations did not correlate with these integrated MRS peaks. On follow-up, changes in these signals also did not correlate with increasing serum valproate levels. The inconsistency of in vivo 1H-MRS signals at varying serum levels and the high detection levels in vitro suggest that valproate signals are missed in vivo because valproate is metabolised or strongly bound, presumably to brain macromolecules.

Adult↗
PubMed2002

Intracerebral pH affects the T2 relaxation time of brain tissue.

Signal changes in activated brain areas are detectable by MRI and MR spectroscopy (MRS). Shifts in pH occur during brain activation. Our aim was to investigate the relationship between changes in pH and T2 relaxation times. T2 was determined in vitro at 24 MHz in various liquids at different pH using a Carr-Purcell-Meiboom-Gill (CPMG) spin-echo sequence. We also studied five Fisher rats were studied at 2.4 tesla with a double-tuneable surface coil. After baseline measurements, potassium cyanide was injected, producing intracerebral acidosis. Alternating series of 1H CPMG spin-echo sequences and 31P spectra were acquired. True T2 relaxation times were calculated from a CPMG multi-echo train. Changes in intracellular pH determined from 31P spectra. In vitro measurements demonstrated a correlation between T2 and pH that could be described by a quadratic fit curve. Depending on the initial pH, changes of 0.2 induced changes in T2 of up to 150 ms. In vivo measurements confirmed these findings. After intraperitoneal injection of a sublethal dose of cyanide, T2 decreased by about 5% in four cases, followed by recovery after 2 h. The in vitro measurements demonstrated that changes in pH can lead to significant signal change on T2- or T2*- weighted images. The dependence of T2 on pH in vitro was confirmed in vivo; it may contribute to signal change in activated brain areas.

Animals↗
PubMed2002

[Standards for safe data exchange in teleradiology exemplified by image and report distribution].

The use of telemedicine is becoming indispensable for a continuous and economical delivery of a high quality of care. However, data protection requirements have to be considered. For the selection of solutions, vendor-independent components based on standards are a prerequisite for a seamless integration into the existing, often heterogeneous, IT infrastructure. The "Internet protocol" TCP/IP and the DICOM standard with it's new security extensions form the basis for an internationally standardized and accepted procedure for a secure interchange of radiological images beyond platform boundaries.

Computer Security↗
PubMed2001

Volume-selective proton MR spectroscopy for in-vitro quantification of anticonvulsants.

Administration of anticonvulsant drugs is clinically monitored by checking seizure frequency and by determining the serum concentration of the drug. In a few reports, drug concentrations in brain parenchyma have been determined using ex vivo techniques. Little is known about the in vivo concentration in the brain parenchyma. Our goals were to characterise the NMR spectra of the anticonvulsants at therapeutic concentrations, to determine the minimum detectable concentrations, and to quantify the drugs noninvasively. Volume-selective 1H-MR spectroscopy (MRS) was performed under standard clinical conditions using a single-voxel STEAM (stimulated-echo acquisition mode) sequence at 1.5 T. Spectra of the anticonvulsants carbamazepine, phenobarbital, phenytoin and valproate were acquired in vitro in hydrous solutions at increasing dilution. Phenytoin, phenobarbital and valproate were detectable below maximum therapeutic serum concentrations. Within therapeutic ranges, there was good agreement between concentrations determined by 1H-MRS and those by standard fluorescence polarisation immunoassay. Due to the absence of signals of brain metabolites, the aromatic protons of phenobarbital, phenytoin and carbamazepine, with resonance lines around 7.4 ppm, allow the drugs to be detected. Valproate, with two resonances around 1.2 ppm, should be differentiable from potential brain metabolites using nonlinear analysis of the brain spectrum. Volume-selective 1H-MRS is therefore expected to be able to monitor anticonvulsant therapy in vivo.

Anticonvulsants↗
PubMed2001

Concepts and data model for a co-operative neurovascular database.

BACKGROUND: Problems of clinical management of neurovascular diseases are very complex. This is caused by the chronic character of the diseases, a long history of symptoms and diverse treatments. If patients are to benefit from treatment, then treatment decisions have to rely on reliable and accurate knowledge of the natural history of the disease and the various treatments. METHODS: Recent developments in statistical methodology and experience from electronic patient records are used to establish an information infrastructure based on a centralized register. RESULTS: A protocol to collect data on neurovascular diseases with technical as well as logistical aspects of implementing a database for neurovascular diseases are described. The database is designed as a co-operative tool of audit and research available to co-operating centres. CONCLUSION: When a database is linked to a systematic patient follow-up, it can be used to study prognosis. Careful analysis of patient outcome is valuable for decision-making.

Adult↗
PubMed2001

Implementation of a dynamic platform-independent DICOM-server.

Hospital-wide image and patient data transfer within heterogeneous hard- and software infrastructures can be facilitated by using standardized communication protocols and data formats such as digital imaging and communications in medicine (DICOM). Each DICOM application entity (AE) usually provides a static and fixed set of services according to its functionality. However, certain security concepts, changing demands of medical users, or restricted hardware capabilities may be more easily addressed by applications that dynamically provide variable subsets of DICOM services. In a new approach, an object-oriented DICOM server framework was developed that served as a basis for assembling various DICOM applications. These applications may be set up dynamically to offer variable subsets of services at runtime, similar to "plug-ins". The framework was designed and implemented in Java in order to provide low-cost platform-independent solutions. As an example, a DICOM server was implemented and tested in a clinical application providing access to MR and CT images through a Java/DICOM viewer. Data retrieval was optimized by storing parts of the image acquisition and patient data into a relational database.

Computer Systems↗
PubMed2001

Simulation and analysis of magnetic resonance elastography wave images using coupled harmonic oscillators and Gaussian local frequency estimation.

New methods for simulating and analyzing Magnetic Resonance Elastography (MRE) images are introduced. To simulate a two-dimensional shear wave pattern, the wave equation is solved for a field of coupled harmonic oscillators with spatially varying coupling and damping coefficients in the presence of an external force. The spatial distribution of the coupling and the damping constants are derived from an MR image of the investigated object. To validate the simulation as well as to derive the elasticity modules from experimental MRE images, the wave patterns are analyzed using a Local Frequency Estimation (LFE) algorithm based on Gauss filter functions with variable bandwidths. The algorithms are tested using an Agar gel phantom with spatially varying elasticity constants. Simulated wave patterns and LFE results show a high agreement with experimental data. Furthermore, brain images with estimated elasticities for gray and white matter as well as for exemplary tumor tissue are used to simulate experimental MRE data. The calculations show that already small distributions of pathologically changed brain tissue should be detectable by MRE even within the limit of relatively low shear wave excitation frequency around 0.2 kHz.

Algorithms↗
PubMed2001

A JAVA-based DICOM server with integration of clinical findings and DICOM-conform data encryption.

The transfer of large amounts of medical data within heterogeneous hard and software infrastructures and the exploitation of distributed resources require a fast, secure, and platform-independent data exchange. To avoid costly vendor-specific solutions, a DICOM server was implemented in JAVA. Data access was enabled via internet browser technology. Relevant patient and image acquisition information was extracted from the DICOM images and stored into a relational database. Patient information such as radiological findings were transferred from the Radiological Information System into the database. Image data were accessed either by a fast preview tool or using a JAVA-based DICOM viewer. Since data security mechanisms are not yet part of the DICOM standard, a DICOM-conform encryption of sensitive patient data was implemented. The method allowed a dynamic selection of the data to be encrypted. Integrating this module into the image server enabled the fast and secure transfer of image data across insecure networks as well as long-term storage on CD-Recordables.

CD-ROM↗
PubMed2001

Diffusion-weighted magnetic resonance imaging in two patients with polycythemia rubra vera and early ischemic stroke.

Polycythemia rubra vera (PRV) is a rare myeloproliferative disorder with a high risk of ischemic stroke. Although thrombosis of large cerebral arteries is the most frequently presumed pathomechanism, various infarct patterns have been described in patients with PRV and ischemic stroke. We report two patients with mild acute ischemic strokes and known PRV, in whom a scattered lesion pattern was detected by diffusion-weighted magnetic resonance imaging (DWI), but was not visible on computed tomography (CT) and conventional magnetic resonance imaging (MRI). Further diagnostic work-up including extra- and transcranial Doppler sonography (ECD, TCD), transesophageal echocardiography (TEE), magnetic resonance angiography and Holter monitoring revealed no obvious sources of cerebral embolism in both cases. However, TEE in one patient demonstrated spontaneous echo contrast (SEC) in the left atrium. In both patients the symptomatology resolved completely. The detection of a scattered infarct pattern by DWI in patients with PRV and acute ischemic stroke has not been reported previously. DWI findings together with the SEC in one patient emphasize the assumption that a prothrombotic state with subsequent arterial embolism rather than local arterial thrombosis may be the underlying pathomechanism of stroke in some patients with PRV. Adding DWI to the diagnostic work-up may help to clarify etiology in patients with PRV and acute ischemic stroke.

Aged↗
PubMed2001

Scattered brain infarct pattern on diffusion-weighted magnetic resonance imaging in patients with acute ischemic stroke.

BACKGROUND AND PURPOSE: Infarct patterns on brain imaging contribute to the etiologic classification of ischemic stroke. However, the association of specific subtypes of infarcts and etiologic mechanisms is often weak, and acute lesions are frequently missed on initial computed tomography (CT). Diffusion-weighted imaging (DWI) is superior in visualizing acute ischemic lesions as compared to CT and conventional magnetic resonance imaging (MRI). In our prospective study, we addressed the question whether a distinct pattern of infarction on DWI is associated with infarct etiology and clinical outcome. METHODS: Sixty-two patients with clinical signs of acute ischemic stroke and negative acute CT upon admission underwent DWI within 10 days after the ictus. Neurological status was documented using the NIH stroke scale. A scattered lesion pattern was defined by at least 2 separate hyperintense DWI lesions within the territory of one of the major cerebral arteries. Ischemic lesions were defined as acute if the region was demarcated strongly hyperintense in all DW images, and if the apparent diffusion coefficient was below normal. RESULTS: In 32 patients, DWI revealed a scattered lesion pattern, while in 30 patients a single acute lesion was detected. In patients with scattered lesions, potential arterial or cardiac embolic sources were detected in 26 patients (81.3%), as compared to 5 patients (16.6%) in the group with single lesions (chi(2) test, p < 0.0001). The neurological status of patients with scattered lesions improved significantly more than among patients with single lesions (Mann-Whitney test, p < 0.0003). CONCLUSION: A scattered lesion pattern on DWI in patients with acute brain infarction and negative initial CT scan is associated with an embolic etiology and may indicate a favorable clinical outcome.

Adult↗
PubMed2000

Histogram-based characterization of healthy and ischemic brain tissues using multiparametric MR imaging including apparent diffusion coefficient maps and relaxometry.

Decreased, renormalized, or increased values of the calculated apparent diffusion coefficient (ADC) are observed in stroke models. A quantitative description of corresponding tissue states using ADC values may be extended to include true relaxation times. A histogram-based segmentation is well suited for characterizing tissues according to specific parameter combinations irrespective of the heterogeneity found for human healthy and ischemic brain tissues. In a new approach, navigated diffusion-weighted images and ADC maps were incorporated into voxel-based parameter sets of relaxation times (T1, T2), and T1- or T2-weighted images, followed by a supervised histogram-based analysis. Healthy tissues were segmented by incorporating T1 relaxation into the data set, ischemic regions by combining T2- or diffusion-weighted images with ADC maps. Mean values of healthy and pathologic tissues were determined, spatial distributions of the parameter vectors were visualized using color-encoded overlays. One to six days after stroke, ischemic regions exhibited reduced relative mean ADC values.

Adult↗
PubMed2000

Prototype of a JAVA/DICOM image server with integrated findings and data security.

The transfer of medical data within heterogeneous hard- and software infrastructures requires platform-independent standardized protocols and data formats such as DICOM. To avoid costly vendor-specific solutions a DICOM server was implemented in JAVA thereby enabling the data access via internet browser technology. The most important patient and image acquisition information were extracted from the DICOM images and stored into a relational database. For an integrated view patient information such as radiological findings were transferred from the Radiological Information System (RIS) into the data base. Image data were accessed either by a fast preview tool or using a DICOM viewer. Since DICOM does not include inherent data security mechanisms, a second tool allowed the DICOM-conform encryption of DCIOM data for a secure long term storage on CD-R or across unsecure networks.

Computer Security↗
PubMed2000

Realization of security concepts for DICOM-based distributed medical services.

Exploiting distributed hard- and software resources for telemedicine requires a fast, secure, and platform-independent data exchange. Standards without inherent security mechanisms such as DICOM may ease non-authorized data access. Therefore, exemplary telemedical data streams were analyzed within the Berlin metropolitan area network using specialized magnetic resonance imaging techniques and distributed resources for data postprocessing. For secure DICOM communication both the Secure Socket Layer Protocol and a DICOM-conform partial encryption of patient-relevant data were implemented. Partial encryption exhibited the highest transfer rate and enabled a secure long-term storage. Different data streams between secured and unsecured networks were realized using partial encryption.

Berlin↗