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At least 91 records · Page 5Linked to original sources
PubMed2001

Organ dose conversion coefficients for 0.1-10 MeV electrons calculated for the VIP-Man tomographic model.

A whole-body tomographic model, called VIP-Man, was recently developed at Rensselaer Polytechnic Institute from the high-resolution color photographic images of the National Library of Medicine's Visible Human Project. An EGS4-based Monte Carlo user code, named EGS4-VLSI, was developed to efficiently transport electrons using the large image data set for VIP-Man. VIP-Man has been used to calculate doses for neutrons and photons. This paper presents a new set of fluence-to-absorbed-dose conversion coefficients for monoenergetic electron beams between 100 keV and 10 MeV for VIP-Man. Irradiation conditions include anterior-posterior, posterior-anterior, right lateral, left lateral, rotational, and isotropic source geometries. Comparisons between organ doses from VIP-Man, which is taller and heavier than the Reference Man, and existing data from mathematical models show significant discrepancies. It appears that even slight differences between body models can cause dramatic dosimetric deviations for low penetrating electron irradiation. This suggests that a single standard body model may poorly represent a large population and may not be acceptable for electron dosimetry.

Electrons↗
PubMed2000

Radiowave propagation from a tissue-implanted source at 418 MHz and 916.5 MHz.

Tissue-implanted ultra-high frequency (UHF) radio devices are being employed in both humans and animals for telemetry and telecommand applications. This paper describes the experimental measurement and electromagnetic modeling of propagation from 418-MHz and 916.5-MHz sources placed in the human vagina. Whole-body homogeneous and semi-segmented software models were constructed using data from the Visible Human Project. Bodyworn radiation efficiencies for a vaginally placed 418-MHz source were calculated using finite-difference time-domain and ranged between 1.6% and 3.4% (corresponding to net body losses of between 14.7 and 18.0 dB). Greater losses were encountered at 916.5 MHz, with efficiencies between 0.36% and 0.46% (net body loss ranging between 23.4 and 24.4 dB). Practical measurements were in good agreement with simulations, to within 2 dB at 418 MHz and 3 dB at 916.5 MHz. The degree of tissue-segmentation for whole-body models was found to have a minimal effect on calculated azimuthal radiation patterns and bodyworn radiation efficiency, provided the region surrounding the implanted source was sufficiently detailed.

Algorithms↗
PubMed1999

A proposal for a standard electronic anthropomorphic phantom for radiotherapy.

To create a database of human male and female computed tomography (CT) slices, the National Library of Medicine organized the "Visible Human Project." Since the male and female data sets provided are approximately 269 MB and 915 MB, respectively, both the size and complexity have been reduced. While making the slices accessible to those with limited computing resources, the production of these reduced data sets also presents a unique opportunity to establish a standard human CT slice library for research in radiation therapy. A brief history of the original data sets is included, as well as details of the reduction process, applications to radiotherapy, and information on accessing these reduced image files.

Adult↗
PubMedDate not supplied

The High-Performance Computing and Communications program, the national information infrastructure and health care.

The High-Performance Computing and Communications (HPCC) program is a multiagency federal effort to advance the state of computing and communications and to provide the technologic platform on which the National Information Infrastructure (NII) can be built. The HPCC program supports the development of high-speed computers, high-speed telecommunications, related software and algorithms, education and training, and information infrastructure technology and applications. The vision of the NII is to extend access to high-performance computing and communications to virtually every U.S. citizen so that the technology can be used to improve the civil infrastructure, lifelong learning, energy management, health care, etc. Development of the NII will require resolution of complex economic and social issues, including information privacy. Health-related applications supported under the HPCC program and NII initiatives include connection of health care institutions to the Internet; enhanced access to gene sequence data; the "Visible Human" Project; and test-bed projects in telemedicine, electronic patient records, shared informatics tool development, and image systems.

Computer Communication Networks↗
PubMed2004

Facilitating arrhythmia simulation: the method of quantitative cellular automata modeling and parallel running.

BACKGROUND: Many arrhythmias are triggered by abnormal electrical activity at the ionic channel and cell level, and then evolve spatio-temporally within the heart. To understand arrhythmias better and to diagnose them more precisely by their ECG waveforms, a whole-heart model is required to explore the association between the massively parallel activities at the channel/cell level and the integrative electrophysiological phenomena at organ level. METHODS: We have developed a method to build large-scale electrophysiological models by using extended cellular automata, and to run such models on a cluster of shared memory machines. We describe here the method, including the extension of a language-based cellular automaton to implement quantitative computing, the building of a whole-heart model with Visible Human Project data, the parallelization of the model on a cluster of shared memory computers with OpenMP and MPI hybrid programming, and a simulation algorithm that links cellular activity with the ECG. RESULTS: We demonstrate that electrical activities at channel, cell, and organ levels can be traced and captured conveniently in our extended cellular automaton system. Examples of some ECG waveforms simulated with a 2-D slice are given to support the ECG simulation algorithm. A performance evaluation of the 3-D model on a four-node cluster is also given. CONCLUSIONS: Quantitative multicellular modeling with extended cellular automata is a highly efficient and widely applicable method to weave experimental data at different levels into computational models. This process can be used to investigate complex and collective biological activities that can be described neither by their governing differentiation equations nor by discrete parallel computation. Transparent cluster computing is a convenient and effective method to make time-consuming simulation feasible. Arrhythmias, as a typical case, can be effectively simulated with the methods described.

Anisotropy↗
PubMed2006

MR thermometry characterization of a hyperthermia ultrasound array designed using the k-space computational method.

BACKGROUND: Ultrasound induced hyperthermia is a useful adjuvant to radiation therapy in the treatment of prostate cancer. A uniform thermal dose (43 degrees C for 30 minutes) is required within the targeted cancerous volume for effective therapy. This requires specific ultrasound phased array design and appropriate thermometry method. Inhomogeneous, acoustical, three-dimensional (3D) prostate models and economical computational methods provide necessary tools to predict the appropriate shape of hyperthermia phased arrays for better focusing. This research utilizes the k-space computational method and a 3D human prostate model to design an intracavitary ultrasound probe for hyperthermia treatment of prostate cancer. Evaluation of the probe includes ex vivo and in vivo controlled hyperthermia experiments using the noninvasive magnetic resonance imaging (MRI) thermometry. METHODS: A 3D acoustical prostate model was created using photographic data from the Visible Human Project. The k-space computational method was used on this coarse grid and inhomogeneous tissue model to simulate the steady state pressure wavefield of the designed phased array using the linear acoustic wave equation. To ensure the uniformity and spread of the pressure in the length of the array, and the focusing capability in the width of the array, the equally-sized elements of the 4 x 20 elements phased array were 1 x 14 mm. A probe was constructed according to the design in simulation using lead zerconate titanate (PZT-8) ceramic and a Delrin plastic housing. Noninvasive MRI thermometry and a switching feedback controller were used to accomplish ex vivo and in vivo hyperthermia evaluations of the probe. RESULTS: Both exposimetry and k-space simulation results demonstrated acceptable agreement within 9%. With a desired temperature plateau of 43.0 degrees C, ex vivo and in vivo controlled hyperthermia experiments showed that the MRI temperature at the steady state was 42.9 +/- 0.38 degrees C and 43.1 +/- 0.80 degrees C, respectively, for 20 minutes of heating. CONCLUSION: Unlike conventional computational methods, the k-space method provides a powerful tool to predict pressure wavefield in large scale, 3D, inhomogeneous and coarse grid tissue models. Noninvasive MRI thermometry supports the efficacy of this probe and the feedback controller in an in vivo hyperthermia treatment of canine prostate.

Acoustics↗
PubMed2003

Comparative analyses of the dynamic properties of the rectum studied by cryo-sections of human cadavers and pelvic CT scans of patients.

Optimization of radiotherapy treatment plans based on dose-volume histograms relies on accurate organ delineation. Hollow organs, such as the rectum, are difficult and time-consuming to delineate owing to unclear visualization of the border between wall tissue and filling. Automated hollow organ delineation would be a valuable tool, but its development depends upon improved understanding of the dynamics of the rectum in response to filling. Two reasonable assumptions proposed in the literature are that (1) the rectal wall tissue along a constant length of the rectal cylinder is preserved over time and (2) the rectal wall tissue is distributed homogeneously along the cylinder. Therefore, variations in wall thickness can be explained by variable rectal filling. To investigate these assumptions, transversal cross-sectional areas enclosed by the outer contour (A(out)) and inner contour (A(in)) of the rectum were recorded from digital photographs of cadaver cryo-sections from the U.S. National Library of Medicine's Visible Human Project. In addition, A(out) and A(in) were recorded from 19 CT scans of 5 of our own patients. The transversal cross-sectional area of the wall of the rectum, A(wall)=A(out)-A(in), was calculated. The data derived both from cryo-sections and repetitive CT scans of patients, revealed that there was a significant correlation between A(wall) and A(out), in contradiction to assumption (1) stated above (male cryo-sections: p<0.001, female cryo-sections: p=0.03, repetitive CT scans p<0.001). Moreover, the mean A(wall) calculated from one CT scan differed significantly from the mean A(wall) from other CT scans and was correlated with the mean A(out), i.e. rectal filling (p<0.001). This finding was confirmed by careful analysis of another study (p=0.001) and opposes assumption (2). Hence, the amount of wall tissue within a constant length of rectum is not preserved over time, but increases with increased filling. This implies that the longitudinal length of the rectum decreases in response to distension of the organ.

Cadaver↗
PubMed2005

Comparative analyses of the dynamic properties of the bladder wall studied by repetitive pelvic CT scans of patients and cryo-sections of cadavers.

In radiotherapy planning systems, delineation of hollow normal tissue organs, such as the bladder, is time-consuming. Automated delineation may presuppose two assumptions: (1) the bladder resembles a spherical shell and (2) the volume of bladder tissue is preserved regardless of the volume of urine (luminal volume) inside. The purpose of the present study was to test these assumptions. 22 CT scans from 7 patients were studied retrospectively. Transverse cross-sectional areas enclosed by the outer contour (A(out)) and inner contour of the bladder (A(in)) were recorded from the images. Hence, the transverse cross-sectional area of the wall, A(wall)=A(out)-A(in), and the volume of bladder tissue at various luminal volumes, could be calculated. To quantify the method uncertainty, the same procedure was applied on three spherical plastic phantoms. The results were also compared with data from the Visible Human Project's photographs of cadaver cryo-sections. Assumption no. 1 stated above, implies that A(wall) is constant regardless of the level of intersection of the sphere. The data from cryo-sections revealed a positive correlation for A(wall) and A(out), in contradiction to assumption no. 1 (p<0.001). The corresponding association derived from the repetitive CT scans of patients was also statistically significant (p<0.001) although linear regression revealed a less steep slope. A relationship was found between the volume of bladder tissue and luminal volume, hence contradicting assumption no. 2 (p<0.001). In conclusion the cross-sectional wall areas of the bladder, measured from patient CT scans, increase slightly with luminal cross-sectional areas in contradiction to expected values derived from a simplistic spherical shell model. In addition, the volume of bladder tissue is related to the luminal volume. Our results may be of practical value when developing automated delineation tools in radiotherapy planning systems.

Cryopreservation↗
PubMed2000

Validation and use of a finite element model of C-2 for determination of stress and fracture patterns of anterior odontoid loads.

OBJECT: The finite element (FE) method is a powerful tool for the analysis of stress patterns of anatomical structures. In this study a highly refined FE model of C-2 was created and validated. The model was then used to characterize stress patterns, predicted fracture patterns, and transitions between Type II and Type III odontoid fractures. METHODS: An anatomically accurate three-dimensional model of C-2 was created from computerized tomography data obtained from the Visible Human Project. The C-2 model was broken down into an FE mesh consisting of 32,815 elements and 40,969 nodes. For validation, the FE model was constrained and loaded to simulate that used in previous biomechanical studies. The validated model was then loaded in an iterative fashion, varying the orientation of the load within the validated range. A matrix of stress plots was created for comparative analysis. Results of the validation testing closely correlated with those obtained in previous biomechanical testing. Pure extension loading produced a Type III stress pattern with maximum stress of 134 MPa. Loading at 45 degrees produced a Type II stress distribution with a maximum stress of 123 MPa. These stresses are within 3% and 11%, respectively, of the reported yield stress of cortical bone (138 MPa). In the second portion of the study, systematic variation in the orientation of the load vector revealed that higher stresses were associated with increased lateral angulation and increasing upward inclination of the load vectors. A transition from a Type III to Type II pattern occurred with lateral orientations greater than 15 degrees and with compressive loads of 45 degrees. CONCLUSIONS: The validated C-2 FE model described in this study both qualitatively and quantitatively was able to simulate the behavior of the C-2 vertebra in biomechanical testing. In this study the authors demonstrate the utility of the FE method when used in conjunction with traditional biomechanical testing.

Algorithms↗
PubMed2003

Prediction and analysis of human thoracic impact responses and injuries in cadaver impacts using a full human body finite element model.

Human thoracic dynamic responses and injuries associated with frontal impact, side impact, and belt loading were investigated and predicted using a complete human body finite element model for an average adult male. The human body model was developed to study the impact biomechanics of a vehicular occupant. Its geometry was based on the Visible Human Project (National Library of Medicine) and the topographies from human body anatomical texts. The data was then scaled to an average adult male according to available biomechanical data from the literature. The model includes details of the head, neck, ribcage, abdomen, thoracic and lumbar spine, internal organs of the chest and abdomen, pelvis, and the upper and lower extremities. The present study is focused on the dynamic response and injuries of the thorax. The model was validated at various impact speeds by comparing predicted responses with available experimental cadaver data in frontal and side pendulum impacts, as well as belt loading. Model responses were compared with similar individual cadaver tests instead of using cadaver corridors because the large differences between the upper and lower bounds of the corridors may confound the model validation. The validated model was then used to study thorax dynamic responses and injuries in various simulated impact conditions. Parameters that could induce injuries such as force, deflection, and stress were computed from model simulations and were compared with previously proposed thoracic injury criteria to assess injury potential for the thorax. It has been shown that the model exhibited speed sensitive impact characteristics, and the compressibility of the internal organs significantly influenced the overall impact response in the simulated impact conditions. This study demonstrates that the development of a validated FE human body model could be useful for injury assessment in various cadaveric impacts reported in the literature. Internal organ injuries, which are difficult to detect in experimental studies with human cadavers, can be more easily identified with a validated finite element model through stress-strain analysis, especially in conjunction with experimental studies.

Journal Article↗
PubMed2005

A finite element model of the lower limb for simulating pedestrian impacts.

A finite element (FE) model of the lower limb was developed to improve the understanding of injury mechanisms of thigh, knee, and leg during car to pedestrian impacts and to aid in the design of injury countermeasures for vehicle front-ends. The geometry of the model was reconstructed from CT scans of the Visible Human Project Database and commercial anatomical databases. The geometry and mass were scaled to those of a 50(th) percentile male and the entire lower limb was positioned in a standing position according to the published anthropometric references. A "structural approach" was utilized to generate the FE mesh using mostly hexahedral and quadrilateral elements to enhance the computational efficiency of the model. The material properties were selected based on a synthesis on current knowledge of the constitutive models for each tissue. Since no reliable data could be found in the literature for flesh, skin, and ligaments, new constitutive properties were determined from experiments on post-mortem human surrogate (PMHS) specimens. Optimization techniques were used to insure consistency among all material test and component test conditions. The validation process of the model included component level tests specific to pedestrian impact loadings from both the literature and more than 30 new PMHS tests. Overall results obtained in the validation indicated improved biofidelity relative to previously published FE models.

Journal Article↗
PubMed1996

Developing a virtual reality-multimedia system for anatomy training.

The University of California, San Diego, School of Medicine's Learning Resources Center is developing a prototype next-generation application for anatomy education which combines virtual reality and multimedia curricular resources. The anatomy lesson utilizes polygon-based 3-D models of the hepatobiliary system created by BioGraphics Inc. of Fort Collins, Colorado which were derived from the National Library of Medicine's Visible Human Project Dataset. This article describes the needs assessment, learning objectives, and preliminary design of the current prototype. The multivariate design, the development strategy for implementing functionalities, and the engineering of critical software interface components are also outlined.

Anatomy↗
PubMed2000

Virtual body structures: a 3D structure development tool from visible human data.

Understanding the visiospatial aspects of anatomic structures is one of the most important aspects of studying gross anatomy. In this paper we are describing a tool that self-constructs 3D virtual body structures (VBS) 'right in-front-of your-eyes'. Furthermore, manipulation capabilities, such as translucent visualization, interactive rotation, translation, and scaling, incorporated into VBS facilitate fundamental learning experience that leads one to 'build 3D models in the mind', providing a validation of computer-assisted individual learning. Creating 3-D virtual body structures from actual human data has long been a dream of many computer scientists and Medical doctors. Now, with the advances in computer hardware and software technologies, our Virtual Body Structure technique, and the Visible Human project, that dream is becoming a reality.

Anatomy, Cross-Sectional↗
PubMed2000

A new research program in medical image data processing.

The National Library of Medicine, in partnership with the National Institute for Dental and Craniofacial Research, the National Eye Institute, the National Science Foundation, the National Institute for Deafness and Other Communication Disorders, and the National Cancer Institute, has founded a software consortium to support the creation of a public resource in high-dimension data processing tools. The initial emphasis of this effort is to provide public software tools in 3D segmentation and deformable and rigid registration, capable of analyzing the head-and-neck anatomy of the Visible Human Project data. The eventual goal is for the consortium to provide the cornerstone of a self-sustaining software community in 3D, 4D and higher dimensional data analysis. The consortium is committed to open-source code, public software including open interfaces supporting connections to a broad range of visualization and graphic user interface platforms.

Anatomy, Cross-Sectional↗
PubMed2001

A realistic model of human structure from the visible human data.

The computer-based 3D models of the human body reported to date suffer from poor spatial resolution. The Visible Human project has delivered high resolution cross-sectional images that are suited for generation of high-quality models. Yet none of the 3D models described to date reflect the quality of the original images. We present a method of segmentation and visualization which provides a new quality of realism and detail. Using the example of a 3D model of the inner organs, we demonstrate that such models, especially when combined with a knowledge base, open new possibilities for scientific, educational, and clinical work.

Anatomy, Cross-Sectional↗
PubMed1999

[Visible human data set and it's application].

The Visible Human Project is an outgrowth of the NLM's 1986 Long-Range Pian. It is creating a complete, anatomically detailed, three-dimensional representations of the male and female human body. This paper makes a brief description about VHP and it's significance, how to get VH data set and how to use it.

Adult↗
PubMed2004

[Bone segmentation in human CT images].

In 3D visualization of human skeleton, distinguishing bones from soft tissue in 2D CT slides is the first and most critical procedure. This article presents the methods for image pre-processing, segmentation and smoothing. 1733 CT images of human body from Visible Human Project provided by the American National Library of Medicine are treated in this paper. We use the technique of Chebyshev uniform approximation filtering for denoising and present a new simple adaptive threshold method in segmentation, which combines the similarity of consecutive slices with the region-growing method. In post-processing, we use the algorithms of mathematical morphology and multi-resolution filtering. The accuracy of segmentation is examined and certified by comparing the segmented images with the original one. The results also demonstrate a wide applicability of the method.

Algorithms↗
PubMed2002

Engineering and algorithm design for an image processing Api: a technical report on ITK--the Insight Toolkit.

We present the detailed planning and execution of the Insight Toolkit (ITK), an application programmers interface (API) for the segmentation and registration of medical image data. This public resource has been developed through the NLM Visible Human Project, and is in beta test as an open-source software offering under cost-free licensing. The toolkit concentrates on 3D medical data segmentation and registration algorithms, multimodal and multiresolution capabilities, and portable platform independent support for Windows, Linux/Unix systems. This toolkit was built using current practices in software engineering. Specifically, we embraced the concept of generic programming during the development of these tools, working extensively with C++ templates and the freedom and flexibility they allow. Software development tools for distributed consortium-based code development have been created and are also publicly available. We discuss our assumptions, design decisions, and some lessons learned.

Algorithms↗