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Results for “Models, Anatomic”

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At least 163 records · Page 9Linked to original sources

PubMed1998

Total knee arthroplasty kinematics. Computer simulation and intraoperative evaluation.

The goal of this work was to develop computer simulations for intraoperative testing of the passive kinematics of knee prostheses. These are based on an anatomic model of the reconstructed joint, represented in the sagittal plane. A femoral component and a tibial component are linked by 3 springs that model the relevant ligaments, with the posterior cruciate providing the primary constraint. The components' behavior at each flexion angle is obtained by minimizing the total strain energy stored in the ligaments. Simulations were performed in vivo on 10 Interax implants (Howmedica International, Stain, UK) and showed good agreement with intraoperative observations, allowing monitoring of new parameters such as contact point motion, ligament strains, and the energetic state of the knee. This work contributes to the comprehension of individual knee kinematics after total knee arthroplasty, to improve long-term results and standardize the evaluation of the results of joint restoration.

Arthroplasty, Replacement, Knee↗

PubMedDate not supplied

Knowledge-based method for segmentation and analysis of lung boundaries in chest X-ray images.

We present a knowledge-based approach to segmentation and analysis of the lung boundaries in chest X-rays. Image edges are matched to an anatomical model of the lung boundary using parametric features. A modular system architecture was developed which incorporates the model, image processing routines, an inference engine and a blackboard. Edges associated with the lung boundary are automatically identified and abnormal features are reported. In preliminary testing on 14 images for a set of 18 detectable abnormalities, the system showed a sensitivity of 88% and a specificity of 95% when compared with assessment by an experienced radiologist.

Algorithms↗

PubMed2003

Graphic-based musculoskeletal model for biomechanical analyses and animation.

The ability to combine physiology and engineering analyses with computer sciences has opened the door to the possibility of creating the 'Virtual Human' reality. This paper presents a broad foundation for a full-featured biomechanical simulator for the human musculoskeletal system physiology. This simulation technology unites the expertise in biomechanical analysis and graphic modeling to investigate joint and connective tissue mechanics at the structural level and to visualize the results in both static and animated forms together with the model. Adaptable anatomical models including prosthetic implants and fracture fixation devices and a robust computational infrastructure for static, kinematic, kinetic, and stress analyses under varying boundary and loading conditions are incorporated on a common platform, the VIMS (Virtual Interactive Musculoskeletal System). Within this software system, a manageable database containing long bone dimensions, connective tissue material properties and a library of skeletal joint system functional activities and loading conditions are also available and they can easily be modified, updated and expanded. Application software is also available to allow end-users to perform biomechanical analyses interactively. This paper details the design, capabilities, and features of the VIMS development at Johns Hopkins University, an effort possible only through academic and commercial collaborations. Examples using these models and the computational algorithms in a virtual laboratory environment are used to demonstrate the utility of this unique database and simulation technology. This integrated system will impact on medical education, basic research, device development and application, and clinical patient care related to musculoskeletal diseases, trauma, and rehabilitation.

Algorithms↗

PubMed2002

Study of the three-dimensional geometry of the central conducting airways in man using computed tomographic (CT) images.

Clinical research on the deposition of inhaled substances (e.g. inhaled medications, airborne contaminants, fumes) in the lungs necessitates anatomical models of the airways. Current conducting airway models lack three-dimensional (3D) reality as little information is available in the literature on the distribution of the airways in space. This is a limitation to the assessment or predictions of the particle deposition in relation to the subject's anatomy. Detailed information on the full topology and morphology of the airways is thus required to model the airway tree realistically. This paper presents the length, diameter, gravity, coronal and sagittal angles that together describe completely the airways in 3D space. The angle at which the airways branch out from their parent (branching angle) and the rotation angle between successive bifurcation planes are also included. These data are from the study of two sets of airways computed tomography (CT) images. One CT scan was performed on a human tracheobronchial tree cast and the other on a healthy male volunteer. The airways in the first nine generations of the cast and in the first six conducting generations of the volunteer were measured using a computer-based algorithm. The data contribute to the knowledge of the lung anatomy. In particular, the spatial structure of the airways is shown to be strongly defined by the central airways with clear angular lobar patterns. Such patterns tend to disappear with a mean gravity, coronal and sagittal angles of 90 degrees in each generation higher than 13-15. The mean branching angle per generation appears independent of the lobe to which the airways belong. Non-planar geometry at bifurcation is observed with the mean (+/- SD) bifurcation plane rotation angle of 79 +/- 410 (n = 229). This angle appears constant over the generations studied. The data are useful for improving the 3D realism of the conducting airway structure modelling as well as for studying aerosol deposition, flow and biological significance of non-planar airway trees using analytical and computational flow dynamics modelling.

Adult↗

PubMed1993

[Prevention of human birth trauma I. Computer-assisted simulation of delivery using magnetic resonance tomography and finite element analysis].

Imaging procedures suitable for diagnosis of cephalopelvic disproportion, such as radiological pelvimetry, computer- or magnetic resonance imaging (MRI) fail to reflect the dynamics of delivery, including deformations of the birth channel as well as of foetal structures. In order to validate findings of imaging procedures in this respect, a method has been developed to perform dynamic, biomechanical postprocessing of the static information obtained from MRI. Using a specially developed software MRI pixel, matrices of the maternal pelvis and the foetal head were colour-coded and--according to the principle of equal density--line data were created. After sectional attribution of the resulting polygones, a three-dimensional mesh of so called Finite Elements (FE) was created, which can then be used for deformation analysis. The foetal head was then moved through the birth channel by means of computed simulation. This allows not only ongoing deformations to be visualised, but also resulting forces can be calculated at any time of the delivery process for any point of the anatomical model. Furthermore, these calculations can be performed assuming various conditions such as different cephalopelvic dimensions and various labour forces or biomechanical properties of the tissues involved. This paper aims at presenting the method and its mode of working by means of one example of a computed birth simulation.

Adult↗

PubMed2006

New needle holder facilitates percutaneous fluoroscopy-guided sacroiliac puncture.

PURPOSE: To evaluate the success of a new guidance device for sacroiliac joint puncture. MATERIAL AND METHODS: The device was first tested on a human anatomical model and thereafter on two groups of patients. In the first group (n=8), the traditional hand-guided method was used, and in the second group (n=10) the needle-holder device. The parameters evaluated in each group were "the number of attempts", defined as the number of skin punctures, and "fluoroscopy-injection time", defined as the time from the beginning of the fluoroscopy to the end of the correct insertion of the needle into the joint. RESULTS: Sacroiliac injection with the new device required significantly fewer attempts (2.1 +/- 2 versus 4.3 +/- 3) and shorter fluoroscopy injection times (8.9 +/- 3 min versus 15 +/- 5 min; P<0.05). CONCLUSION: The new guidance device makes sacroiliac joint injection easier and prevents unnecessary exposure to radiation during the procedure.

Fluoroscopy↗

PubMed2005

Development of the female voxel phantom, NAOMI, and its application to calculations of induced current densities and electric fields from applied low frequency magnetic and electric fields.

This paper outlines the development of a 2 mm resolution voxel model, NAOMI (aNAtOMIcal model), designed to be representative of the average adult female. The primary medical imaging data were derived from a high-resolution MRI scan of a 1.65 m tall, 23 year old female subject with a mass of 58 kg. The model was rescaled to a height of 1.63 m and a mass of 60 kg, the dimensions of the International Commission on Radiological Protection reference adult female. There are 41 tissue types in the model. The application of NAOMI to the calculations of induced current densities and electric fields from applied low frequency magnetic and electric fields is described. Comparisons are made with values from the male voxel model, NORMAN. The calculations were extended from 50 Hz up to 10 MHz. External field reference levels are compared with the ICNIRP guidelines.

Adult↗

PubMed1991

A simple height-specific and rate-specific step test for children.

Recently an anatomic model was reported for adults that standardized the platform height for step tests using an individual's stature and a specified hip angle. In order to determine if the model could be used to predict the platform height for children, platform heights were calculated and hip angles were measured in 146 boys and 140 girls ages 6 to 18 years who were divided into four age groups (6 to 8, 9 to 11, 12 to 15, and 16 to 18 years old). There were no statistical differences between measured and calculated hip angles in any of the age groups. In order to determine the validity for predicting maximal oxygen consumption from stepping using a calculated platform height, three step tests were employed using one platform height and stepping frequencies of 22, 26, or 30 ascents/min. Each of the tests was administered to 93 6- to 18-year-olds. Correlation coefficients between the 15-second recovery heart rate after stepping and maximal oxygen consumption measured on a treadmill were .80 at 30 ascents/min, .79 at 26 ascents/min, and .81 at 22 ascents/min. Each of the correlation coefficients was significant at the P less than .01 level. It can be concluded that the model is valid for standardizing the platform height for children for use with a single stage step test for estimating maximal oxygen consumption.

Adolescent↗

PubMed2006

Musculoskeletal exam and joint injection training for internal medicine residents.

We developed a musculoskeletal education intervention for internal medicine residents consisting of lectures, anatomic models, and a joint injection clinic. Written tests, observed musculoskeletal exams, and self-confidence scales were administered to 27 internal medicine residents before and after the intervention. Improvement was found in observed physical exam and self-reported confidence levels in performing knee injections. Confidence in shoulder injection skills improved, but remained low. Improved scores on written examination, though statistically significant, were not educationally significant. This single-institution pilot study demonstrates that a simple educational program results in improved knee and shoulder examination skills and confidence in performing knee injections.

Ambulatory Care↗

PubMed1993

Finite element analysis of poor distal contact of the femoral component of a cementless hip endoprosthesis.

The difficulty of achieving good distal contact between a cementless hip endoprosthesis and the femur is well established. This finite element study investigates the effect on the stress distribution within the femur due to varying lengths of distal gap. Three-dimensional anatomical models of two different sized femurs were generated, based upon computer tomograph scans of two cadaveric specimens. A further six models were derived from each original model, with distal gaps varying from 10 to 60 mm in length. The resulting stress distributions within these were compared to the uniform contact models. The extent to which femoral geometry was an influencing factor on the stress distribution within the bone was also studied. Lack of distal contact with the prosthesis was found not to affect the proximal stress distribution within the femur, for distal gap lengths of up to 60 mm. In the region of no distal contact, the stress within the femur was at normal physiological levels associated with the applied loading and boundary conditions. The femoral geometry was found to have little influence on the stress distribution within the cortical bone. Although localized variations were noted, both femurs exhibited the same general stress distribution pattern.

Biomechanical Phenomena↗

PubMed1985

Computed tomography of the calcaneus: normal anatomy.

The normal sectional anatomy of the calcaneus was studied as the background for interpretation of computed tomography (CT) of fractures. Multiplanar CT examination of the normal calcaneus was obtained, and sections were matched with a simplified anatomic model. Sectional anatomy in the four most important planes is described. This facilitates three-dimensional understanding of the calcaneus from sections and interpretation of CT sections obtained in any atypical plane.

Adult↗

PubMed2004

[The historical evolution of obstetrician formation].

The evaluation of the historical development of obstetrician formation presents features of great modernity. At the end of the XVIII century in Florence the first School of Obstetrics for midwives was established. In the School two relevant complementary formative approaches were privileged: ex cathedra didactics and clinical training. The basic tools for these educational methodologies were constituted by handbook production and by wax anatomical models, the latter a field for the meeting and confrontation of surgeons and craftsmen. The historical-social scenario in which this original evolution took place was Tuscany society in the period of Enlightenment, that promoted the formation of professional figures capable of managing natural childbirth in an autonomous way, while nevertheless placing them under a previously lacking health policy control. In this cultural environment particularly impressive was the influence of J.P. Frank (Austria and Lombardy), but also present were other forces, deriving from other European countries, that aimed at including the formation of obstetricians in a scientific programme, thus excluding an unguarded non-structured training.

Education, Medical↗

PubMed2006

Segmenting the visible human female.

Web-based three-dimensional Virtual Body Structures (W3D-VBS) is an interactive image-based anatomical training system over the Internet. It uses segmented low-resolution Visible Human Male (LR-VHM) data to dynamically explore, select, highlight, label, extract, manipulate, and stereoscopically palpate 3D virtual anatomical models with a haptic device. The segmentation results presented in this paper for the Visible Human Female (VHF) and the high resolution Visible Human Male (HR-VHM) have been obtained using our segmentation tools. Segmenting the HR-VHM was an easier task as we use the segmented shapes and label information of existing LR-VHM data, with the same image content. This is not the case for the VHF and we needed to develop a special tool, Segm-VHF, which allows us to integrate the VHF dataset into W3D-VBS.

Female↗

PubMedDate not supplied

[Possible applications of a method for 3D reconstruction of CT image data. OP-planning, finishing of individual alloplastic implants for replacement of cranial and maxillofacial bone structures].

A method for the three-dimensional reconstruction of CT-image data permits manufacturing of natural size anatomical models thus enabling preoperative measurements of relevant parameters (length, areas, and volumes). The methods described allow for new perspectives in preoperative planning of dental implants, particularly for the maxillary problem area. The use of 3D image data for manufacturing individual alloplastic implants simplifies the exact reconstruction of symmetrical bone structures, which up to now was impossible to achieve with conventional methods. Applications in the fields of orthodontic surgery and in neurological surgery are suggested. Refinement of available techniques is possible by means of additional segmentation of soft tissues, and by implementation of more sophisticated software for better visualisation and smoothly shaped surfaces. Future applications may even include aesthetic surgery.

Adult↗

PubMedDate not supplied

Development of a completely implantable total artificial heart.

In conjunction with engineering and physiologic requirements, anatomic fit is a fundamental problem that must be carefully addressed in the design of a truly feasible implantable total circulatory support system. To facilitate the conceptualization, a three-dimensional anatomic model of an average adult thorax was developed from a data bank of 14 human cadavers, 100 radiographs, 18 computerized tomographs, 4 nuclear magnetic resonance (NMR) studies, and 31 cineangiograms. The location and orientation of the valves, the atrial chambers, venae cavae, and pulmonary hili were found to be the most critical information. As a result, configuration of a one piece, completely implantable total artificial heart (E4T system) with the hydraulic actuator placed between the two ventricles was defined and sized to provide an output of 8 L/min at 120 beats/min. The device was designed to be positioned through a midsternotomy similar to the natural ventricles (in the pericardial sac toward the left chest cavity), and the ports were carefully designed to eliminate the risk of compression of critical cardiovascular structures. Validation of the design was conducted with an E4T model implanted in three human adult cadavers, two of which were submitted to NMR imaging after the device was implanted and the incision closed. Excellent fit was observed in all cadavers, and analysis of the several sagittal, transverse, and coronal NMR images showed no compression of the natural internal structures.

Heart, Artificial↗

PubMed1977

External rotational injury of tha ankle joint with displacement of the talus.

The mechanism of second-degree external rotational injury of the ankle, with fracture of the lower end of the fibula, is discussed with reference to experiments on an anatomical model. It is concluded that with this type of injury there is lateral displacement of the talus because the deltoid ligament is ruptured, but there is no diastasis of the inferior tibiofibular syndesmosis. The results of conservative treatment of 10 patients with second-degree external rotational injury of tha ankle are reviewed.

Adolescent↗

PubMed1993

A flexible, generic model for anatomic shape: application to interactive two-dimensional medical image segmentation and matching.

A representation called a radial contour model (RCM) is described for two-dimensional anatomic shapes. The model, which is a type of a geometric constraint network (GCN), is both flexible, in that it can deform to fit a particular instance of an anatomic shape, and generic, in that it captures all examples of a particular anatomic shape class. The model is implemented in a program, called SCANNER (version 0.7), for interactive model-based two-dimensional image segmentation and matching. Use of the model allows the segmenter to direct the search for edges in the image, and to fill in edges where none are present. Evaluations were done using models of 15 cross-sectional shapes appearing on CT images from 16 patients. Results from 480 trials show that the model-based approach reduces segmentation time by nearly a factor of 3 over manual methods, and correctly classifies 72.9% of the contours. The results not only suggest that the RCM will be useful for several current medical image segmentation tasks, but also support the hypothesis that geometric constraint networks are a viable approach to anatomic shape representation.

Artificial Intelligence↗

PubMed2001

Vascular grafts in the rat model: an anatomic study.

Vascular grafts in animal models have been used extensively in the microsurgical laboratory, and the rat offers an excellent source of graft to meet these needs. In this study, we compiled a list of vessels that were previously identified in experimental literature for use as vascular grafts in the rat model. We then dissected and measured both arterial and venous grafts taken from these sites in 12 adult rats. The surgical procedure for approaching each vascular graft was recorded. The diameter and harvestable length, the start and end points, and the number of branches of the graft were tabulated. We believe that these data will provide valuable insight applicable to the use of the rat vascular graft in microsurgical research and training.

Animals↗