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At least 1,711 records · Page 95Linked to original sources
PubMed2004

[Accuracy of diameter measurement in vitro using automated software for CT angiography: effect of convolution kernels].

The purpose of this study was to evaluate the accuracy of diameter measurement in vitro using automated software for CT angiography with five convolution kernels. Vascular models with three diameters (about 3, 5, and 8 mm) in three materials (water, oil, and air) were scanned by helical CT. Five convolution kernels were used for reconstruction. The accuracy of diameter measurement was affected by the diameter of the vascular model, material around the model, and convolution kernels. Selection of the proper convolution kernels may improve accuracy.

Angiography↗
PubMed2004

[Non-invasive coronary angiography with 16 multidetector-row spiral computed tomography: a comparative study with invasive coronary angiography].

INTRODUCTION AND OBJECTIVES: Non-invasive coronary artery angiography by 16 multidetector-row spiral computed tomography is a novel diagnostic tool whose reliability is still unclear. The aim of our study was to compare this technique with invasive coronary angiography. PATIENTS AND METHOD: A total of 31 selected patients were examined with both angiographic methods. Non-invasive studies were performed with a helical computer tomography system (Toshiba Aquilion 16-slices). A contrast agent was injected into a peripheral vein, and cross-sectional images were reconstructed with a slice thickness of 0.5 mm or 1.0 mm. Findings from both techniques were analyzed according to a predetermined segmented anatomical model of the coronary artery. The detection and relevance of coronary artery lesions were evaluated, and lesions with a reduction in diameter of more than 50% were considered significant. RESULTS: Non-invasive coronary angiography yielded an appropriate assessment in 88.4% of the coronary artery segments. The reasons that prevented correct segment evaluation were extensive coronary calcifications, inappropriate breath-hold, motion artefacts and small vessel size. Sensitivity and specificity for the detection of significant coronary lesions with the non-invasive method were 75% and 91%, respectively. Sensitivity and specificity for individual coronary artery segments were as follows: proximal, 89% and 93%; medial, 87% and 90%; distal, 50% and 90%; and secondary branches, 62% and 92%. CONCLUSIONS: Non-invasive coronary artery angiography with 16 multidetector-row computed tomography is a powerful diagnostic tool, especially for the evaluation of the proximal and medial segments of the major coronary arteries.

Adult↗
PubMedDate not supplied

Training and assessment of laparoscopic skills.

Laparoscopic surgery is gaining popularity among the surgical community. While its prevalence expands, the need for reliable training and assessment tools is becoming increasingly important. Laparoscopic skills are not an innate behavior, nor can they be easily mimicked, and can only be acquired through hands-on training. A consensus exists among physicians that establishment and evaluation of technical skill in surgical training programs are inadequate and in need of improvement. A validated, reliable bench model that could train and assess could be standardized and provide numerous benefits including determination of which medical students should consider a career in surgery, valuable feedback to residents, a tracking mechanism of resident performance, a possible certification and recertification tool, and to allow for interinstitutional comparison. To this end, several potentially successful bench models testing dexterity, hand-eye coordination, and depth perception have been developed. A few models have been proven to be both valid and reliable indicators of technical skill. Although the future remains uncertain, enough groundwork has been laid to begin incorporating technical skill training and assessment into surgical training programs.

Clinical Competence↗
PubMed2004

Dynamic three-dimensional reconstruction and modeling of cardiovascular anatomy in children with congenital heart disease using biplane angiography.

Modeling and simulation of cardiovascular biomechanics and fluid dynamics from patient-specific data is a continuing topic of research investigation. Several methodologies utilizing CT, MRI and ultrasound to re-create the three-dimensional anatomy of the cardiovascular system have been examined. Adaptation of these models to pediatric applications has not been studied as extensively. There is significant need for such techniques in pediatric congenital heart disease since local anatomy may exhibit highly unusual geometry, and three-dimensional information would be of significant use for surgical and interventional planning, biomechanical and fluid dynamic simulation, and patient counseling. We report here on the adaptation and application of a three-dimensional reconstruction technique that utilizes bi-plane angiographic images as the base data sets. The method has been validated in a variety of adult imaging situations including coronary artery imaging and intervention. The method uses a skeletonization approach whereby local centerline, diameter, branching and tortuosity of the vasculature are obtained to create the three-dimensional model. Ten patients with a variety of etiology were imaged and 3D reconstructions were obtained. Excellent images were obtained of complex anatomy including the highly branched pulmonary vasculature and Fontan surgical connections. The data were then translated into solid and surface models to facilitate viewing, export into computational fluid dynamic grids, and into files suitable for stereo lithography fabrication (STL). This method appears promising for the dynamic study of complex cardiovascular anatomy found in congenital heart disease. Optimization of the method to facilitate on-line reconstruction and simulation are currently ongoing.

Algorithms↗
PubMed2004

[Models and computation methods of EEG forward problem].

The research of EEG is of grat significance and clinical importance in studying the cognitive function and neural activity of the brain. There are two key problems in the field of EEG, EEG forward problem and EEG inverse problem. EEG forward problem which aims to get the distribution of the scalp potential due to the known current distribution in the brain is the basis of the EEG inverse problem. Generally, EEG inverse problem depends on the accuracy and efficiency of the computational method of EEG forward problem. This paper gives a review of the head model and corresponding computational method about EEG forward problem studied in recent years.

Algorithms↗
PubMed2004

[Method of calculating self-shielding of the human critical organs in the anthropomorphic phantom].

Proposed is a procedure of calculating the self-screening function of a point on the human body model. The procedure has been developed for the anthropomorphic phantom approved in Russian standard GOST 25645.203-83. The procedure allows extrapolation of the self-shielding calculations to a different body model and a partially protected human body (intra- and extravehicular spacesuit, etc). Results can be useful in precise determination of radiation risks with consideration of the organs self-shielding factor.

Algorithms↗
PubMedDate not supplied

Accuracy of a robotic system for the reproduction of condylar movements: a preliminary report.

OBJECTIVE: Methods in restorative dentistry have to meet stringent accuracy requirements. The accuracy of robotic systems used for the reproduction of condylar movements has not been determined. The purpose of this study was to assess the accuracy of the robot system, ROSY, a robotlike electronic simulator (developed by the author) that reproduces condylar movements previously recorded on a patient. METHOD AND MATERIALS: The simulator consists of a custom-designed ultrasonic system that records mandibular movements in all three dimensions (vertical, horizontal, and coronal) with six degrees of freedom. The simulator automatically reproduces all movements around these axes with a robotic system with six stepper motors. The accuracy of the simulator was measured for all directions in space by registering eccentric jaw positions on both sides of 10 subjects in two ways: (1) by the ultrasound registration system; and (2) simultaneously with an interocclusal recording medium. The standard deviation and interquartile range of the differences between the measurements based on these two approaches were used to statistically describe the accuracy of ROSY. RESULTS: The accuracy of the entire system was better than 0.28 mm. CONCLUSION: The electronic simulator comes with an accuracy that may render it suitable for clinical applications.

Computer Simulation↗
PubMed2003

[Three-dimensional modeling of mandibular distraction].

Facial hemi-atrophy affects 1 in 4000 or 5000 children. We propose treating this deformation of the 1st branchial arch with the "bone distraction" lengthening technique first described by Ilizarov in the 1950s, which has already been employed with the mandible. We have modelled mandibular distraction in facial hemi-atrophy patients and discuss the benefits of such pre-surgical planning encompassing the assistance of pre- and post-operative as well as surgically coordinated orthodontic therapy. Using X scanner views of a 5 year-old girl patient, we have developed a distraction-simulation software, which makes the pathological side harmonious with the healthy side along the medial sagittal plane. In order to obtain facial symmetry, put bones in balance, and orient the occlusal plane horizontally, essential requisites of occlusal stability, it is necessary: to employ a 2 or 3-dimensional distractor, to pre-plan the distraction and screw positioning, to set up a fixed orthodontic treatment plan prior to beginning distraction therapy.

Child, Preschool↗
PubMedDate not supplied

Applications of rapid prototyping technology in maxillofacial prosthetics.

PURPOSE: The purpose of this study was to compare the accuracy, required time, and potential advantages of rapid prototyping technology with traditional methods in the manufacture of wax patterns for two facial prostheses. MATERIALS AND METHODS: Two clinical situations were investigated: the production of an auricular prosthesis and the duplication of an existing maxillary prosthesis, using a conventional and a rapid prototyping method for each. Conventional wax patterns were created from impressions taken of a patient's remaining ear and an oral prosthesis. For the rapid prototyping method, a cast of the ear and the original maxillary prosthesis were scanned, and rapid prototyping was used to construct the wax patterns. For the auricular prosthesis, both patterns were refined clinically and then flasked and processed in silicone using routine procedures. Twenty-six independent observers evaluated these patterns by comparing them to the cast of the patient's remaining ear. For the duplication procedure, both wax patterns were scanned and compared to scans of the original prosthesis by generating color error maps to highlight volumetric changes. RESULTS: There was a significant difference in opinions for the two auricular prostheses with regard to shape and esthetic appeal, where the hand-carved prosthesis was found to be of poorer quality. The color error maps showed higher errors with the conventional duplication process compared with the rapid prototyping method. CONCLUSION: The main advantage of rapid prototyping is the ability to produce physical models using digital methods instead of traditional impression techniques. The disadvantage of equipment costs could be overcome by establishing a centralized service.

Computer-Aided Design↗
PubMed2003

Development of a training tool for endotracheal intubation: distributed augmented reality.

The authors introduce a tool referred to as the Ultimate Intubation Head (UIH) to train medical practitioners' hand-eye coordination in performing endotracheal intubation with the help of augmented reality methods. In this paper we describe the integration of a deployable UIH and present methods for augmented reality registration of real and virtual anatomical models. The assessment of the 52 degrees field of view optics of the custom-designed and built head-mounted display is less than 1.5 arc minutes in the amount of blur and astigmatism, the two limiting optical aberrations. Distortion is less than 2.5%. Preliminary results of the registration of a physical phantom mandible on its virtual counterpart yields less than 3mm rms. in registration. Finally we describe an approach to distributed visualization where a given training procedure may be visualized and shared at various remote locations. Basic assessments of delays within two scenarios of data distribution were conducted and reported.

Computer Simulation↗
PubMed2002

Multimodal simulation of laparoscopic Heller myotomy using a meshless technique.

In this work we focus our attention on developing a surgical simulator for performing laparoscopic Heller myotomy using force feedback. A meshless numerical technique, the method of finite spheres, is used for the purpose of physically based, real time haptic and graphical rendering of soft tissues. Localized discretization allows display of deformations in the vicinity of the tool tip as well as interaction forces at high update rates (kHz). Novel cutting algorithms are implemented using point-based representation of anatomical models. Graphical rendering is accomplished by using a recently developed volumetric rendering technique known as splatting.

Computer Graphics↗
PubMed2004

Soft tissue deformation using a Hierarchical Finite Element Model.

Simulating soft tissue deformation in real-time has become increasingly important in order to provide a realistic virtual environment for training surgical skills. Several methods have been proposed with the aim of rendering in real-time the mechanical and physiological behaviour of human organs, one of the most popular being Finite Element Method (FEM). In this paper we present a new approach to the solution of the FEM problem introducing the concept of parent and child mesh within the development of a hierarchical FEM. The online selection of the child mesh is presented with the purpose to adapt the mesh hierarchy in real-time. This permits further refinement of the child mesh increasing the detail of the deformation without slowing down the simulation and giving the possibility of integrating force feedback. The results presented demonstrate the application of our proposed framework using a desktop virtual reality (VR) system that incorporates stereo vision with integrated haptics co-location via a desktop Phantom force feedback device.

Connective Tissue↗
PubMed2005

Genestrace: phenomic knowledge discovery via structured terminology.

The era of applied genomic medicine is quickly approaching accompanied by the increasing availability of detailed genetic information. Understanding the genetic etiology behind complex, multi-gene diseases remains an important challenge. In order to uncover the putative genetic etiology of complex diseases, we designed a method that explores the relationships between two major terminological and ontological resources: the Unified Medical Language System (UMLS) and the Gene Ontology (GO). The UMLS has a mainly clinical emphasis; Gene Ontology has become the standard for biological annotations of genes and gene products. Using statistical and semantic relationships within and between the two resources, we are able to infer relationships between disease concepts in the UMLS and gene products annotated using GO and its associated databases. We validated our inferences by comparing them to the known gene-disease relationships, as defined in the Online Mendelian Inheritance in Man's morbidmap (OMIM). The proof-of-concept methods presented here are unique in that they bypass the ambiguity of the direct extraction of gene or disease term from MEDLINE. Additionally, our methods provide direct links to clinically significant diseases through established terminologies or ontologies. The preliminary results presented here indicate the potential utility of exploiting the existing, manually curated relationships in biomedical resources as a tool for the discovery of potentially valuable new gene-disease relationships.

Computational Biology↗
PubMed2005

[Implants placement using a novel computerized tactile imaging navigation system].

An implant locating system has been developed. The system contains a stent that maps the jaw bone at the implantation site through the tissue, sends a signal to a computer with a CT scan of the jaw on it, and superimposes the position of the stent on the jaw so that a dental surgeon could angle the implant for placement without requiring to raise a flap to expose the bone. Using a novel tactile technology the system allows safe, accurate, and simple implant placement and design. The ILS software allows: 1. Importing of CT data. 2. Marking a dental arc on the computerized jaw image. 3. Planning of implant location and position on a 3-D view. 4. Affixation of the ILS to the jaw, followed by registration of the stent. 5. Navigated osteotomy and implant placement.

Computer Simulation↗
PubMedDate not supplied

[The numerical Hatze-model: also qualified for calculations on children?].

The aim of this study was to find out whether the Hatze-model, which is specifically designed for adults, is suitable for calculations on children as well. By means of that program it is possible to calculate various parameters of the human body. After the collection of data and analysis of the results according to Hatze it becomes evident that this model provides good results only for the calculation of the total body mass. As regards the body segments, there are significant under- and overestimations. The same applies to the calculation of mean body density. Indeed there is a significant gender dimorphism indicating that girls have a higher fraction of body fat than boys. However, the values are far below those described in the literature. Due to the formula, the values of the centres of gravity are linear and congruent in both sides of the body. Interpretation of the results is difficult, as there are no valid reference values. Furthermore the program is not able to take characteristic shapes and proportions of children into account. For this reason 88% of the children are defined as either pregnant or obese. In summary, the study shows that the present model should not be used to calculate children and the human models have to be designed specifically for children.

Accidents, Traffic↗