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At least 127 records · Page 7Linked to original sources
PubMed2004

Thin sectional anatomy, three-dimensional reconstruction and visualization of the heart from the Chinese Visible Human.

The research aimed to provide sectional anatomic and three-dimensional (3D) virtual anatomic bases for imaging diagnosis and surgical operation by the use of data from the heart of the first Chinese digitized Visible Human. Data from the series of thin sections of the heart were analyzed and input into an SGI workstation, and 3D reconstruction and virtualization of the heart were performed. Each image of sectional anatomy was clear and the 3D structures of the heart were reconstructed in their entirety. All reconstructed structures can be displayed by multiple structural and color modes, individually or jointly, and can be rotated continuously in any plane. The model of the virtual heart clearly showed fine structures of the heart in random orientation. The dataset of the sectional anatomy provides a fine and integrated morphologic base for imaging diagnosis. The 3D reconstructed images clearly show the internal and entire structures of the heart.

Anatomy, Cross-Sectional↗
PubMed2007

3D heart model for computer simulations in cardiac surgery.

For a satisfactory computer simulation, a model, which imitates a natural situation, is needed. The Human heart is an irregular 3D object and thus difficult to reproduce. Basic data was taken from Visible Human Dataset (VHD), National Library of Medicine. The heart area was cut out of the original cross-sections and different tissues segmented. All the slices also had to be aligned to assure precise overlapping of the structures. A 3D computer heart model with the resolution of 1mm was designed. The heart model was dedicated to simulations of heat transfer during heart surgery however, it is applicable also to other medical simulations.

Cardiac Surgical Procedures↗
PubMed2006

The use of sparse CT datasets for auto-generating accurate FE models of the femur and pelvis.

The finite element (FE) method when coupled with computed tomography (CT) is a powerful tool in orthopaedic biomechanics. However, substantial data is required for patient-specific modelling. Here we present a new method for generating a FE model with a minimum amount of patient data. Our method uses high order cubic Hermite basis functions for mesh generation and least-square fits the mesh to the dataset. We have tested our method on seven patient data sets obtained from CT assisted osteodensitometry of the proximal femur. Using only 12 CT slices we generated smooth and accurate meshes of the proximal femur with a geometric root mean square (RMS) error of less than 1 mm and peak errors less than 8 mm. To model the complex geometry of the pelvis we developed a hybrid method which supplements sparse patient data with data from the visible human data set. We tested this method on three patient data sets, generating FE meshes of the pelvis using only 10 CT slices with an overall RMS error less than 3 mm. Although we have peak errors about 12 mm in these meshes, they occur relatively far from the region of interest (the acetabulum) and will have minimal effects on the performance of the model. Considering that linear meshes usually require about 70-100 pelvic CT slices (in axial mode) to generate FE models, our method has brought a significant data reduction to the automatic mesh generation step. The method, that is fully automated except for a semi-automatic bone/tissue boundary extraction part, will bring the benefits of FE methods to the clinical environment with much reduced radiation risks and data requirement.

Algorithms↗
PubMed2004

S-values calculated from a tomographic head/brain model for brain imaging.

A tomographic head/brain model was developed from the Visible Human images and used to calculate S-values for brain imaging procedures. This model contains 15 segmented sub-regions including caudate nucleus, cerebellum, cerebral cortex, cerebral white matter, corpus callosum, eyes, lateral ventricles, lenses, lentiform nucleus, optic chiasma, optic nerve, pons and middle cerebellar peduncle, skull CSF, thalamus and thyroid. S-values for C-11, O-15, F-18, Tc-99m and I-123 have been calculated using this model and a Monte Carlo code, EGS4. Comparison of the calculated S-values with those calculated from the MIRD (1999) stylized head/brain model shows significant differences. In many cases, the stylized head/brain model resulted in smaller S-values (as much as 88%), suggesting that the doses to a specific patient similar to the Visible Man could have been underestimated using the existing clinical dosimetry.

Algorithms↗
PubMed2005

Adjoint Monte Carlo method for prostate external photon beam treatment planning: an application to 3D patient anatomy.

Recently, the theoretical framework of the adjoint Monte Carlo (AMC) method has been developed using a simplified patient geometry. In this study, we extended our previous work by applying the AMC framework to a 3D anatomical model called VIP-Man constructed from the Visible Human images. First, the adjoint fluxes for the prostate (PTV) and rectum and bladder (organs at risk (OARs)) were calculated on a spherical surface of 1 m radius, centred at the centre of gravity of PTV. An importance ratio, defined as the PTV dose divided by the weighted OAR doses, was calculated for each of the available beamlets to select the beam angles. Finally, the detailed doses in PTV and OAR were calculated using a forward Monte Carlo simulation to include the electron transport. The dose information was then used to generate dose volume histograms (DVHs). The Pinnacle treatment planning system was also used to generate DVHs for the 3D plans with beam angles obtained from the AMC (3D-AMC) and a standard six-field conformal radiation therapy plan (3D-CRT). Results show that the DVHs for prostate from 3D-AMC and the standard 3D-CRT are very similar, showing that both methods can deliver prescribed dose to the PTV. A substantial improvement in the DVHs for bladder and rectum was found for the 3D-AMC method in comparison to those obtained from 3D-CRT. However, the 3D-AMC plan is less conformal than the 3D-CRT plan because only bladder, rectum and PTV are considered for calculating the importance ratios. Nevertheless, this study clearly demonstrated the feasibility of the AMC in selecting the beam directions as a part of a treatment planning based on the anatomical information in a 3D and realistic patient anatomy.

Dose-Response Relationship, Radiation↗
PubMed2005

Estimation of patient dose from radiopharmaceuticals using voxel models.

The aim of this study was to demonstrate the advantages of patient dosimetry using voxel models and to present sets of dose estimates for patients of different gender and size. These models offer greater realism with respect to organ shape and topology than the well-established Medical Internal Radiation Dose (MIRD)-type mathematical models. At the National Research Centre for Environment and Health (GSF), specific absorbed fractions have been previously calculated for 4 male and 3 female voxel models, representing different age and stature, for a wide range of source organs. For this study, estimates both for established and new radiopharmaceuticals were performed using biokinetic data from International Commission on Radiological Protection (ICRP). The above calculations allowed for comparison to the MIRD technique in relation to the resulting absorbed organ and effective doses. Furthermore, data sets representing a range of voxel phantoms were investigated. It was found that dose differences among the voxel models can amount up to a factor of 3.

Adult↗
PubMed2005

Comparison of effective doses from various monoenergetic particles based on the stylised and the VIP-Man tomographic models.

This study compares the effective doses from a MIRD-type stylised model with those derived from the scaled-down version of the tomographic VIP-Man model for photon, electron, neutron and proton beams. The effective dose results from these two models show that they differ from each other within approximately 10% for common high-energy photon beams, within approximately 16% for neutrons, and within approximately 4% for high-energy proton beams. However, for low-energy protons and common electron beams, the effective doses can be different in >100%. It is concluded that the use of a single tomographic models will not improve the operational radiation protection dosimetry involving external beam exposures.

Adult↗
PubMed2004

Advanced technologies in plastic surgery: how new innovations can improve our training and practice.

Over the last two decades, virtual reality, haptics, simulators, robotics, and other "advanced technologies" have emerged as important innovations in medical learning and practice. Reports on simulator applications in medicine now appear regularly in the medical, computer science, engineering, and popular literature. The goal of this article is to review the emerging intersection between advanced technologies and surgery and how new technology is being utilized in several surgical fields, particularly plastic surgery. The authors also discuss how plastic and reconstructive surgeons can benefit by working to further the development of multimedia and simulated environment technologies in surgical practice and training.

Case Management↗
PubMed2006

Heterogeneous three-dimensional anatomical and electrophysiological model of human atria.

Investigating the mechanisms underlying the genesis and conduction of electrical excitation in the atria at physiological and pathological states is of great importance. To provide knowledge concerning the mechanisms of excitation, we constructed a biophysical detailed and anatomically accurate computer model of human atria that incorporates both structural and electrophysiological heterogeneities. The three-dimensional geometry was extracted from the visible female dataset. The sinoatrial node (SAN) and atrium, including crista terminalis (CT), pectinate muscles (PM), appendages (APG) and Bachmann's bundle (BB) were segmented in this work. Fibre orientation in CT, PM and BB was set to local longitudinal direction. Descriptions for all used cell types were based on modifications of the Courtemanche et al. model of a human atrial cell. Maximum conductances of Ito, IKr and ICa,L were modified for PM, CT, APG and atrioventricular ring to reproduce measured action potentials (AP). Pacemaker activity in the human SAN was reproduced by removing IK1, but including If, ICa,T, and gradients of channel conductances as described in previous studies for heterogeneous rabbit SAN. Anisotropic conduction was computed with a monodomain model using the finite element method. The transversal to longitudinal ratio of conductivity for PM, CT and BB was 1:9. Atrial working myocardium (AWM) was set to be isotropic. Simulation of atrial electrophysiology showed initiation of APs in the SAN centre. The excitation spread afterwards to the periphery near to the region of the CT and preferentially towards the atrioventricular region. The excitation extends over the right atrium along PM. Both CT and PM activated the right AWM. Earliest activation of the left atrium was through BB and excitation spread over to the APG. The conduction velocities were 0.6ms-1 for AWM, 1.2ms-1 for CT, 1.6ms-1 for PM and 1.1ms-1 for BB at a rate of 63bpm. The simulations revealed that bundles form dominant pathways for atrial conduction. The preferential conduction towards CT and along PM is comparable with clinical mapping. Repolarization is more homogeneous than excitation due to the heterogeneous distribution of electrophysiological properties and hence the action potential duration.

Action Potentials↗
PubMed2005

Geometric modeling of the human normal cerebral arterial system.

We propose an anatomy-based approach for an efficient construction of a three-dimensional human normal cerebral arterial model from segmented and skeletonized angiographic data. The centerline-based model is used for an accurate angiographic data representation. A vascular tree is represented by tubular segments and bifurcations whose construction takes into account vascular anatomy. A bifurcation is defined quantitatively and the algorithm calculating it is given. The centerline is smoothed by means of a sliding average filter. As the vessel radius is sensitive to quality of data as well as accuracy of segmentation and skeletonization, radius outlier removal and radius regression algorithms are formulated and applied. In this way, the approach compensates for some inaccuracies introduced during segmentation and skeletonization. To create the frame of vasculature, we use two different topologies: tubular and B-subdivision based. We also propose a technique to prevent vessel twisting. The analysis of the vascular model is done on a variety of data containing 258 vascular segments and 131 bifurcations. Our approach gives acceptable results from anatomical, topological and geometrical standpoints as well as provides fast visualization and manipulation of the model. The approach is applicable for building a reference cerebrovascular atlas, developing applications for simulation and planning of interventional radiology procedures and vascular surgery, and in education.

Cerebral Arteries↗
PubMedDate not supplied

Creating and simulating skeletal muscle from the visible human data set.

Simulation of the musculoskeletal system has important applications in biomechanics, biomedical engineering, surgery simulation, and computer graphics. The accuracy of the muscle, bone, and tendon geometry as well as the accuracy of muscle and tendon dynamic deformation are of paramount importance in all these applications. We present a framework for extracting and simulating high resolution musculoskeletal geometry from the segmented visible human data set. We simulate 30 contact/collision coupled muscles in the upper limb and describe a computationally tractable implementation using an embedded mesh framework. Muscle geometry is embedded in a nonmanifold, connectivity preserving simulation mesh molded out of a lower resolution BCC lattice containing identical, well-shaped elements, leading to a relaxed time step restriction for stability and, thus, reduced computational cost. The muscles are endowed with a transversely isotropic, quasi-incompressible constitutive model that incorporates muscle fiber fields as well as passive and active components. The simulation takes advantage of a new robust finite element technique that handles both degenerate and inverted tetrahedra.

Algorithms↗
PubMedDate not supplied

LOD map--A visual interface for navigating multiresolution volume visualization.

In multiresolution volume visualization, a visual representation of level-of-detail (LOD) quality is important for us to examine, compare, and validate different LOD selection algorithms. While traditional methods rely on ultimate images for quality measurement, we introduce the LOD map--an alternative representation of LOD quality and a visual interface for navigating multiresolution data exploration. Our measure for LOD quality is based on the formulation of entropy from information theory. The measure takes into account the distortion and contribution of multiresolution data blocks. A LOD map is generated through the mapping of key LOD ingredients to a treemap representation. The ordered treemap layout is used for relative stable update of the LOD map when the view or LOD changes. This visual interface not only indicates the quality of LODs in an intuitive way, but also provides immediate suggestions for possible LOD improvement through visually-striking features. It also allows us to compare different views and perform rendering budget control. A set of interactive techniques is proposed to make the LOD adjustment a simple and easy task. We demonstrate the effectiveness and efficiency of our approach on large scientific and medical data sets.

Algorithms↗
PubMed2006

Three dimensional reconstruction of the pancreas based on the virtual Chinese human--female number 1.

OBJECTIVE: To study the three dimensional (3D) reconstruction and 3D visualisation of the pancreas and create anatomy of the digitalised visual pancreas so as to construct a concrete basis for virtual operation and surgical operation on pancreas. METHODS: The digital imaging data of pancreas, duodenum, common bile duct, arteries, and veins were obtained from the virtual Chinese human--female 1 (VCH-F1). The image data were investigated and 380 images ascertained of pancreas picked up from images numbers 2617 to 2996. Finally, the images from number 2574 to 3017 were adopted to segment and processed using ACDSee and Photoshop so as to reconstruct 3D pancreas digitally. The data of pancreatic surfaces were transformed into Visualization Toolkit (VTK). The GUI program written with VC+ was used to display this VTK file and realise 3D visualisation of the pancreas. RESULTS: 3D reconstruction and visualisation of the pancreas and the peri-pancreatic structures (the duodenum, the common bile duct,the inferior vena cava, the portal vein vessels, the aorta, the coeliac trunk vessels) was successful. The 3D and visualised pancreas manifested itself with its complete structure as well as its adjacency to other tissues. CONCLUSION: The 3D reconstruction and 3D visualisation of the pancreas based on the digital data of VCH-F1 produces a digitally visualised pancreas, which promises a novel method for virtual operation on the pancreas, clinical operation on the pancreas, and anatomy of 3D visualised pancreas.

Arteries↗
PubMed2004

Model of local temperature changes in brain upon functional activation.

Experimental results for changes in brain temperature during functional activation show large variations. It is, therefore, desirable to develop a careful numerical model for such changes. Here, a three-dimensional model of temperature in the human head using the bioheat equation, which includes effects of metabolism, perfusion, and thermal conduction, is employed to examine potential temperature changes due to functional activation in brain. It is found that, depending on location in brain and corresponding baseline temperature relative to blood temperature, temperature may increase or decrease on activation and concomitant increases in perfusion and rate of metabolism. Changes in perfusion are generally seen to have a greater effect on temperature than are changes in metabolism, and hence active brain is predicted to approach blood temperature from its initial temperature. All calculated changes in temperature for reasonable physiological parameters have magnitudes <0.12 degrees C and are well within the range reported in recent experimental studies involving human subjects.

Body Temperature↗
PubMed2006

[The transparent body: medical imaging and popular culture in the twentieth century].

In today's societies, successful new medical imaging technologies have focused unprecedented attention on the inside of the human body. These techniques have jumped the walls of the biomedical field per se, penetrating the fields of culture and law. The article traces a genealogy of twentieth-century medical techniques used to visualize the human body and brain, from X-rays to the more sophisticated CTs, MRIs, and PET scans. It explores the changes that these ever more numerous visualization techniques have occasioned in our corporality and examines how these technologies have been received in the courtroom and in popular culture, especially in literature, movies, and magazines.

Culture↗
PubMed2004

Surface morphology of kidney, ureters and urinary bladder models based on data from the visible human male.

The aim of the present work was to create a simplified high-resolution three-dimensional model of kidneys, ureters and urinary bladder in a data form suitable for finite element/volume based numerical simulations. The exterior morphology of the organs was based on images from the Visible Human Male data set. In both the right and left kidney, there were defined their topographic relations to the neighbouring anatomical structures. This model of kidneys, ureters and urinary bladder will be incorporated into the model of The Visible Human Male abdomen and pelvis and it is ready to be used for numerical simulations in urinary system biomechanics.

Humans↗
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↗