Biomedical subjects

J Ehrhardt

Publications and source records attributed to J Ehrhardt.

At least 19 recordsLinked to original sources

PubMed2006

Computer-assisted analysis of 4D cardiac MR image sequences after myocardial infarction.

OBJECTIVES: Spatial-temporal MR image sequences of the heart contain information about shape and motion changes and pathological structures after myocardial infarction. In this paper a Heart Analysis Tool (HeAT) for the quantitative analysis of 4D MR image sequences of infarct patients is presented. METHODS: HeAT supports interactive segmentation of anatomical and pathological structures. Registration of Cine- and DE-MR image data is applied to enable their combined evaluation during the analysis process. Partitioning of the myocardium in segments enables the analysis with high local resolution. Corresponding segments are generated and used for inter/intrapatient comparison. Quantitative parameters were extracted and visualized. RESULTS: Parameters like endocard movement in the infarcted area of six infarct patients were computed in HeAT. Parameters in the infarct area show the expected dysfunctional characteristics. Based on theses parameters passive endocardial movement and myocardial areas with decreased contraction could be identified. CONCLUSION: In contrast to other software tools HeAT supports the combination of contour information of Cine-MR and DE-MR, local analysis with high resolution and inter/intra patient comparison. HeAT enables an observer-independent evaluation of the complex cardiac image data. Using HeAT in further studies can increase the understanding of left ventricle (LV) remodeling.

Algorithms↗

PubMed2004

Human muscle precursor cell regeneration in the mouse host is enhanced by growth factors.

The aim of this study was to optimize human muscle formation in vivo from implanted human muscle precursor cells. We transplanted donor muscle precursor cells (MPCs) prepared from postnatal or fetal human muscle into immunodeficient host mice and showed that irradiation of host muscle significantly enhanced muscle formation by donor cells. The amount of donor muscle formed in cryodamaged host muscle was increased by exposure of donor cells to growth factors before their implantation into injured host muscle. Insulin-like growth factor type I (IGF-I) significantly increased the amount of muscle formed by postnatal human muscle cells, but not by fetal human MPCs. However, treatment of fetal muscle cells with IGF-I, in combination with basic fibroblast growth factor and plasmin, significantly increased the amount of donor muscle formed. In vivo, human MPCs formed mosaic human-mouse muscle fibers, in which each human myonucleus was associated with a zone of human sarcolemmal protein spectrin.

Animals↗

PubMed2004

Atlas-based recognition of anatomical structures and landmarks and the automatic computation of orthopedic parameters.

OBJECTIVE: This paper describes methods for the automatic atlas-based segmentation of bone structures of the hip, the automatic detection of anatomical point landmarks and the computation of orthopedic parameters to avoid the interactive, time-consuming pre-processing steps for the virtual planning of hip operations. METHODS: Based on the CT data of the Visible Human Data Sets, two three-dimensional atlases of the human pelvis have been built. The atlases consist of labeled CT data sets, 3D surface models of the separated structures and associated anatomical point landmarks. The atlas information is transferred to the patient data by a non-linear gray value-based registration algorithm. A surface-based registration algorithm was developed to detect the anatomical landmarks on the patient's bone structures. Furthermore, a software tool for the automatic computation of orthopedic parameters is presented. Finally, methods for an evaluation of the atlas-based segmentation and the atlas-based landmark detection are explained. RESULTS: A first evaluation of the presented atlas-based segmentation method shows the correct labeling of 98.5% of the bony voxels. The presented landmark detection algorithm enables the precise and reliable localization of orthopedic landmarks. The accuracy of the landmark detection is below 2.5 mm. CONCLUSION: The atlas-based segmentation of bone structures, the atlas-based landmark detection and the automatic computation of orthopedic measures are suitable to essentially reduce the time-consuming user interaction during the pre-processing of the CT data for the virtual three-dimensional planning of hip operations.

Algorithms↗

PubMed2001

Three-dimensional planning and simulation of hip operations and computer-assisted construction of endoprostheses in bone tumor surgery.

OBJECTIVE: This article presents the VIRTOPS (VIRTual Operation Planning in Orthopaedic Surgery) software system for virtual preoperative planning and simulation of hip operations. The system is applied to simulate the endoprosthetic reconstruction of the hip joint with hemipelvic replacement, and supports the individual design of anatomically adaptable, modular prostheses in bone tumor surgery. The virtual planning of the operation and the construction of the individual implant are supported by virtual reality techniques. The central step of the operation planning procedure, the placement of the cutting plane in the hip bone, depends strongly on the tumor's position. Segmentation of the tumor and the bones in MR and CT data, as well as fusion of MR and CT image sequences, is necessary to visualize the tumor's position within the hip bone. MATERIALS AND METHODS: Three-dimensional models of the patient's hip are generated based on CT image data. A ROI-based segmentation algorithm enables the separation of the bone tumor in multispectral MR image sequences. A special registration method using segmentation results has been developed to transfer CT and MR data into one common coordinate system. During the 3D planning process, the surgeon simulates the operation and defines the position and geometry of the custom-made endoprosthesis. Stereoscopic visualization and 3D input devices facilitate navigation and 3D interaction in the virtual environment. Special visualization techniques such as texture mapping, color coding of quantitative parameters, and transparency support the determination of the correct position and geometry of the prosthesis. RESULTS AND CONCLUSIONS: The VIRTOPS system enables the complete virtual planning of hip operations with endoprosthetic reconstruction, as well as the optimal placement and design of endoprostheses. After the registration and segmentation of CT and MR data, 3D visualizations of the tumor within the bone are generated to support the surgeon during the planning procedure. In the virtual planning environment, individually adapted endoprostheses can be constructed without the need to generate expensive solid 3D models. Furthermore, different operation strategies can be compared easily. Three-dimensional images and digital movies generated during the virtual operation planning can be used for case documentation and patient information purposes.

Algorithms↗

PubMed2001

Cerebral activation during anal and rectal stimulation.

While the rectum is innervated by visceral afferents, the anal canal is innervated by the somatosensory pudendal nerve. The representation of these two central domains of intestinal sensations in the human brain is largely unknown. Nonpainful pneumatic stimulation of the anal canal and the distal rectum using event-related functional magnetic resonance imaging (fMRI) was performed in eight healthy subjects. Subjective scaling of sensations revealed no differences in unpleasantness and pain during both stimuli. Both types of stimuli revealed fMRI activation in secondary somatosensory, insula, cingular gyrus, left inferior parietal, and right orbitofrontal cortex. Anal stimulation resulted in additional activation of primary sensory and motor cortex, supplementary motor area, and left cerebellum. We concluded that viscerorectal and somatosensory anal stimulation predominantly differ in their primary sensory activation and additional activation in motor areas. This motor response following aversive somatosensory stimuli may be caused by a reflexive avoidance reaction which is not observed after the more diffuse experienced visceral stimulation.

Adult↗

PubMed2001

Atlas-based segmentation of bone structures to support the virtual planning of hip operations.

Two 3-D digitised atlases of a female and a male pelvis were generated to support the virtual 3-D planning of hip operations. The anatomical atlases were designed to replace the interactive, time-consuming pre-processing steps for the virtual operation planning. Each atlas consists of a labelled reference CT data set and a set of anatomical point landmarks. The paper presents methods for the automatic transfer of these anatomical labels to an individual patient data set. The labelled patient data are used to generate 3-D models of the patient's bone structures. Besides the anatomical labelling, the determination of measures, like angles, distances or sizes of contact areas, is important for the planning of hip operations. Thus, algorithms for the automatic computation of orthopaedic parameters were implemented. A first evaluation of the presented atlas-based segmentation method shows a correct labelling of 98.5% of the bony voxels.

Algorithms↗

PubMed2001

Simulation of hip operations and design of custom-made endoprostheses using virtual reality techniques.

In this paper a system for the virtual planning of hip operations with endoprosthetic reconstruction and its application in bone tumor surgery is described. The system enables the simulation of the operation and the construction of a custom-made implant depending on the chosen resection planes and the patient's anatomy. During the planning process integrated virtual reality techniques facilitate the interaction with the three-dimensional (3D) medical objects. Stereo viewing improves the perception of the 3D nature of bone structures and tumors. In comparison to conventional planning procedures, different operation strategies and their influence on the geometry of the custom-made endoprosthesis can be easily compared. Furthermore, the combination of multi-modal image information (CT and MR) enables an accurate 3D visualization of the bone tumor within the bone.

Arthroplasty, Replacement, Hip↗

PubMed2000

Virtual planning of hip operations and individual adaption of endoprostheses in orthopaedic surgery.

The introduction of virtual reality techniques in medicine opens up new possibilities for the planning of interventions. The presented software system for virtual operation planning in orthopaedic surgery (VIRTOPS) enables the virtual preoperative 3D planning and simulation of pelvis and hip operations. It is used to plan operations of bone tumours with endoprosthetic reconstruction of the hip based on multimodal image information. The operation and the endosprothetic reconstruction of the pelvis are simulated using virtual reality techniques. Stereoscopic visualisation techniques and 3D input devices support the 3D interaction with the virtual 3D models. The main task of the preoperative planning process is the individual design of an anatomically adaptable modular prosthesis. The placement and the design of the endoprosthesis are supported by different functions and visualisation techniques. The resulting 3D images and movies can be used for the documentation of the operation planning procedure, as well as, for the preoperative information of the patient.

Arthroplasty, Replacement, Hip↗

PubMed2000

The nursing shortage: implications for perianesthesia nursing in the 21st century.

Nursing shortages are not a new problem, and in fact, seem to come around on an almost cyclical basis. Although nursing shortages are not unusual, this first shortage of the 21st century exhibits unique characteristics that could undermine the very fiber of nursing, and healthcare in general. Members of the ASPAN Board of Directors attended the Nursing Shortage: Practical Solutions Conference conducted by The Forum on Health Care Leadership and sponsored by Cross Country University (a continuing education company part of Cross Country Staffing, Boca Raton, FL) and Curtin Calls, held in September of 1999 (Ft Lauderdale, FL). This article provides an overview of information gathered at that conference and will also explore the challenges and opportunities that this shortage poses to the specialty of perianesthesia nursing.

Humans↗

PubMed2000

An anatomical atlas to support the virtual planning of hip operations.

Two three-dimensional digitized atlases of a female and a male pelvis were generated to support the virtual 3D-planning of hip operations. Beside the anatomical labeling of bone structures the determination of orthopedic measures, like angles, distances or sizes of contact areas, is important for the planning of hip operations. Thus, each atlas consists of labeled reference CT data sets, a set of landmarks as well as definitions of orthopedic measures and methods for their automatic computation. Furthermore, methods for the automatic transfer of anatomical labels from the atlas to an individual data set are presented resulting in three-dimensional models of the patient's bone structures. The anatomical atlases are designed to replace the interactive, time-consuming pre-processing steps for the virtual 3D operation planning.

Anatomy, Artistic↗

PubMed1999

Subchronically applied phencyclidine fails to disrupt prepulse inhibition in rats.

To simulate psychosis in rats, the psychotomimetic agent phencyclidine (PCP, 5.0 mg/kg) was administered either by daily pulsatile injections or by continuous delivery with subcutaneously implanted, PCP-loaded controlled release polymers for a 5 day period. The acoustic startle response (ASR) and the prepulse inhibition (PPI) were then assessed 15 and 60 min as well as 24 h after the PCP application was discontinued. An impaired PPI occurred only under the acute influence of the last PCP injection, i.e. 15 and 60 min after last PCP treatment when it had previously been given in a pulsatile manner but not when it was administered continuously. The ASR to unpaired stimuli after PCP was not modified. These findings suggest that disruption of PPI occurs only under the acute influence of PCP and that PPI deficits are not primarily the consequence of structural brain damage which PCP produces.

Acoustic Stimulation↗

PubMed1999

Computer-assisted planning and simulation of hip operations using virtual three-dimensional models.

In this paper a new software system for virtual preoperative planning and simulation of hip operations is presented. The system simulates the endoprosthetic reconstruction of the hip joint with hemipelvic replacement for bone tumor patients and supports the individual design of anatomically adaptable, modular prostheses. Three-dimensional models of the patient's hip are generated based on CT data. The surgeon simulates the operation and defines the position and shape of the custom-made endoprosthesis. Stereoscopic visualization and 3D input devices facilitate the navigation and interaction in the virtual environment. Special visualization techniques like texture mapping, color coding of quantitative parameters or transparency support the determination of the correct position and shape of the prosthesis. Furthermore, the system can be used for patient information or educational tasks.

Arthroplasty, Replacement, Hip↗

PubMed1998

Dose and cost considerations for relocation after nuclear accidents.

The results of a comprehensive study of the dose and cost considerations for relocation after nuclear accidents are presented in this paper. These results include the quantification of the dependence of area affected by relocation on dose intervention level and source term, the countermeasures implementation cost-benefit estimate, as well as the application of cost-benefit analysis to optimize the dose intervention level for relocation. In order to explicitly consider the distribution of individual dose among the exposed population to determine the optimal dose intervention level for relocation, the concept of individual dose evaluation function has been introduced in the present work.

Cost-Benefit Analysis↗

PubMed1997

A bioadaptive approach for experimental pain research in humans using laser-evoked brain potentials.

In order to find an experimental approach counteracting habituation in experimental pain research using short infrared laser stimulation in humans we developed a bioadaptive method based on subject's report on painfulness of stimulation (pain report; PR). After determination of the initial relationship between the energy of the laser stimulus and the corresponding PRs, the approach continuously adjusts the intensity of noxious stimuli so that PR is kept constant across time. Each difference between the PR evoked by the actual laser stimulus and the desired PR leads to an increase or decrease of the laser output energy value for the next stimulation with the desired PR proportional to the PR difference as well as to the slope of the initial correlation function between laser energy and corresponding PRs. This method has been applied in a study with nine volunteers. Results show that the approach leads to a constant PR by increasing the laser output energy by 0.01 mJ/s per mm2 on the average. Furthermore, an analysis of the laser-evoked brain potentials (LEPs) recorded from Cz was performed for the first and second half of stimuli. However, no significant changes in latencies or amplitudes of the main LEP components recorded at 210 ms (N210) and 350 ms (P350) were found. The method seems to be useful for different approaches in experimental and clinical pain research.

Adult↗

PubMed1997

Loss of lifetime due to radiation exposure-averaging problems.

A new method is presented for assessing a years of life lost (YLL) due to stochastic effects caused by the exposure to ionizing radiation. The widely accepted method from the literature uses a ratio of means of two quantities, defining in fact the loss of life as a derived quantity. We start from the real stochastic nature of the quantity (YLL), which enables us to obtain its mean values in a consistent way, using the standard averaging procedures, based on the corresponding joint probability density functions needed in this problem. Our method is mathematically different and produces lower values of average YLL. In this paper we also found certain similarities with the concept of loss of life expectancy among exposure induced deaths (LLE-EID), which is accepted in the recently published UNSCEAR report, where the same quantity is defined as years of life lost per radiation induced case (YLC). Using the same data base, the YLL and the LLE-EID are calculated and compared for the simplest exposure case-the discrete exposure at age a. It is found that LLE-EID overestimates the YLL, and that the magnitude of this overestimation reaches more than 15%, which depends on the effect under consideration.

Adolescent↗

PubMed1996

Radiographic presentation of pulmonary tuberculosis in severely immunosuppressed HIV-seropositive patients.

Although the presence of typical postprimary or "reactivation" pattern tuberculosis (TB) on chest radiograph (CXR) strongly suggests TB infection in adults, the sensitivity of this finding, particularly in severely immunosuppressed human immunodeficiency virus (HIV) patients, is unclear. To investigate this issue, HIV status, CD4 counts, and CXR findings of all adult patients with culture-proven TB admitted to a tertiary-care hospital over a 2-year period were retrospectively studied. CXRs were classified as typical for postprimary TB if they showed upper lobe opacities with or without cavitation. No attempt was made to correlate the actual clinical phase of TB infection (primary versus postprimary) with CXR patterns, largely because differentiating primary from postprimary TB in HIV patients is difficult due to high anergy rates and inability to skin-test-convert. Of 46 patients who had chest radiographs and medical records documenting HIV status available for review, 23 were HIV-seropositive and 23 were HIV-seronegative. Of 22 HIV-seropositive patients whose CD4 counts were available, 18 (82%) had CD4 counts of < 200 cells/microL. Only 2 of these 18 (11%) had CXRs showing a typical postprimary TB pattern, whereas all 4 (100%) patients with CD4 counts of > 200 cells/microL and 18 of 23 (78%) non-HIV patients had CXRs typical for postprimary TB (P < .005). It was concluded that HIV-seropositive patients with TB and CD4 counts of < 200 cells/microL frequently present with chest radiographs atypical for postprimary TB, including normal CXRs. Typical postprimary TB CXR findings are not sensitive for diagnosing pulmonary TB in this population.

AIDS-Related Opportunistic Infections↗

PubMed1993

Intelligence and brain structure in normal individuals.

OBJECTIVE: This study was designed to evaluate the relation between intelligence and a variety of measures of brain structure. METHOD: Magnetic resonance imaging scans were used to measure the volume of the intracranial cavity, cerebral hemispheres, lateral ventricles, temporal lobes, hippocampus, caudate, and cerebellum, as well as the overall volume of gray matter, white matter, and CSF, in 67 healthy, normal volunteers. Intelligence was measured with the Wechsler Adult Intelligence Scale--Revised. RESULTS: Full-scale IQ was found to be significantly correlated with intracranial, cerebral, temporal lobe, hippocampal, and cerebellar volume but not with caudate and lateral ventricle volume. There were also significant correlations of full-scale, verbal, and performance IQ with overall gray matter volume but not with white matter or CSF volume. Gender differences were noted in the pattern and number of correlations between the volume of the brain and its subregions and full-scale, verbal, and performance IQ. CONCLUSIONS: The results suggest that the size of some cerebral structures may account for a significant, but modest, proportion of the variance in human intelligence.

Brain↗

PubMed1993

Voxel processing techniques for the antemortem study of neuroanatomy and neuropathology using magnetic resonance imaging.

BRAINBLAST, a program that uses voxel processing, was developed in order to produce high-fidelity three-dimensional reconstructions of the brain. Four steps were used to produce images: washing away cerebrospinal fluid (via histogramming), dissecting away the blood vessels (via a connectivity heuristic), highlighting the sulci and gyri (via a lighting model), and resampling the interior contents of the brain. After reconstruction, the images can be resampled, rotated, written on, measured, or redissected. The technique has a variety of applications: study of individual variation in sulcal and gyral patterns, evaluation of structure/function relationships, measurement of volumes or subregions using anatomically defined landmarks, and teaching of neuroanatomy.

Brain↗