Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Models, Anatomic”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,315 records · Page 73Linked to original sources
PubMedDate not supplied

A survey on hair modeling: styling, simulation, and rendering.

Realistic hair modeling is a fundamental part of creating virtual humans in computer graphics. This paper surveys the state of the art in the major topics of hair modeling: hairstyling, hair simulation, and hair rendering. Because of the difficult, often unsolved problems that arise in all these areas, a broad diversity of approaches are used, each with strengths that make it appropriate for particular applications. We discuss each of these major topics in turn, presenting the unique challenges facing each area and describing solutions that have been presented over the years to handle these complex issues. Finally, we outline some of the remaining computational challenges in hair modeling.

Computer Graphics↗
PubMed1992

Evaluation of nasal resistance data in active anterior rhinomanometry with special reference to clinical usefulness and test-retest analysis.

A systematic evaluation of the most common parameters used in active anterior rhinomanometry was made with artificial tube and cadaver models and patient recordings. The clinical suitability of the parameters was judged on their calculability, reproducibility and power to separate the recordings into meaningful degrees of patency. It was shown that resistance at 150 Pa was not calculable in 30% of the measurements because such a high pressure gradient was not achieved during quiet breathing. The power to separate the grades of obstruction was good with all the models but in the test-retest analysis, it was shown that the power to detect +/- 20% variation in repeated measurement in the same person with a decongested nose was not sufficient with the resistance at 150 ml/s and at radius 100. The coefficient of resistance W = P/V2 at peak flow and resistance at radius 200 showed good capability to separate the grades of obstruction, they are measurable in all recordings, their reproducibility is good and thus, they are recommended for clinical practice.

Adolescent↗
PubMed2005

How we do it: the Bradford grommet trainer: a model for training in myringotomy and grommet insertion.

Myringotomy and grommet insertion is the most common operative procedure in otological practice. We describe a simple, cheap and effective model for the junior trainee to develop the skills required for myringotomy and grommet insertion without compromising patient safety. As the materials required for our model are more readily available, it is more likely to gain widespread acceptance in ENT training.

Clinical Competence↗
PubMed1991

A method for the construction of simulated root canals in clear resin blocks.

A method for the construction of simulated root canals in clear resin blocks is described. The canals are inexpensive, simple to produce and are of high enough quality for use in both undergraduate and continuing education. With minor modifications, the canals can also be used for research, particularly during the assessment of instruments and preparation techniques.

Dental Pulp Cavity↗
PubMed1996

The use of a modelling technique to investigate the root canal morphology of mandibular incisors.

The prime objective of this study was to develop and test a method of modelling the dental root canal system using a vinyl resin, type UCAR-VYHD. It also aimed to verify if the resin models allow a three-dimensional evaluation of those features of the pulpal morphology of human permanent mandibular incisor teeth, which might be associated with periodontal disease. One hundred and eleven freshly extracted teeth were studied. Pre-extraction clinical records and periapical radiographs were used to deduce the presence or absence of periodontal disease. Each extracted tooth was radiographed in two perpendicular planes before being opened by conventional orthograde endodontic technique, and photographed in a scanning electron microscope. The patent pulp space was then obturated with the vinyl resin. Scanning electron photomicrographs of the resin replicas and of the teeth were compared with the earlier radiographic images to correlate the morphological findings. The numbers of root canals and apical foramina were recorded. This study showed that in mandibular incisors with periodontal disease there was a relatively low incidence of lateral canals (7.2%). The modelling technique was found to be reliable, reproducible, and provided sufficient detail to allow three-dimensional analysis of root canal morphology.

Adult↗
PubMed2005

The imaging of root canal obturation using micro-CT.

AIM: To examine the potential and accuracy of micro-computed tomography (micro-CT) for imaging of filled root canals. METHODOLOGY: The root canals of five extracted maxillary teeth were shaped manually with K-files. After irrigation and drying, the root canals were filled by lateral condensation using gutta-percha cones and AH plus (Dentsply Maillefer, Ballaigues, Switzerland) as sealer. The filled root canals were examined by micro-CT at resolutions <11 microm. Three-dimensional reconstructions of the root canal fillings were made. The roots were sectioned histologically and standard photographs of the sectioned surfaces were taken. Digitized photographic images and the corresponding micro-CT sections were correlated qualitatively by superimposition. Quantitative morphometric data were obtained with respect to the surface area of the root canal filling and the individual gutta-percha points of the histological and the micro-CT sections. Pearson correlation coefficients were calculated. RESULTS: There was a good qualitative correlation between the images from the histological and the micro-CT sections. The fillings were clearly differentiated from the root canal walls. Individual gutta-percha cones and sealer were discernable. Pearson correlation coefficients showed a highly significant correlation between the two methods (P < 0.001) with respect to the area of the complete root canal filling (r = 0.992) and the gutta-percha cones (r = 0.968). CONCLUSIONS: The micro-CT technique was a highly accurate and nondestructive method for the evaluation of root canal fillings and its constituents. Qualitative and quantitative correlation between histological and micro-CT examination of root canal fillings was high.

Dental Pulp Cavity↗
PubMed1996

The social body and the biomechanical body: can they coexist in nurse education?

The curricula of tertiary nursing courses usually involve a number of complementary strands. These include biological sciences, social sciences, behavioural sciences, other support subjects and clinical units. These different strands each, to some extent, present the nursing student with a dilemma as they may present entirely different models of the body. Explorations of this dilemma show that students are also being presented with different models of illness and different conceptions of appropriate health care response to illness. The question is then raised as to which of these approaches most accurately reflects the realities of nursing practice.

Biomechanical Phenomena↗
PubMed1979

Determination of membrane thickness distribution from orthogonal intercepts.

This report deals with the reconstruction of the distribution of membrane thickness T from that of orthogonal length Lo, measured in random section planes. In such planes the membrane appears as a band and the linear distance from one of its boundaries perpendicular to the opposite one is the length of the orthogonal intercept. Using a membrane model, an integral equation relating the probability density functions of orthogonal intercept length f(lo) and membrane thickness g(tau) is derived. Relations between moments are derived and the analytic solution to the problem of reconstructing g(tau) from f(lo) is given. The parametric approach by which it assumed that g(tau) has some known analytic form with unknown parameters is considered, and the use of a suggested analytic form for describing the thickness distribution of the human glomerular basement membrane is discussed.

Basement Membrane↗
PubMed1995

Radiographic amelocemental junction and alveolar crest: effect of X-ray beam angulation.

The effect of X-ray beam angulation on the radiographic images of the amelocemental junction (ACJ) and alveolar crest (AC) and their positions relative to one another were assessed using a new laboratory model for radiographic studies. A total of 39 teeth with 62 usable approximal surfaces were included in the investigation. When all tooth types were combined, changes in vertical or horizontal angulation from baseline through 20 degrees had no significant effect on the distance between the marked (true) ACJ and marked (true) AC. However, the distance between the apparent (radiographic) ACJ and apparent (radiographic) AC was significantly reduced by varying the beam angulation in either a vertical or horizontal direction. Results for individual tooth types were qualitatively similar but larger discrepancies were found in molars followed by premolars and incisors. The results emphasize the importance of maintaining the ideal X-ray beam, tooth, bone, film relationship when taking radiographs for the assessment of periodontal destruction.

Acrylic Resins↗
PubMed1977

Teaching models of abnormal infants.

A technique is described for the construction of life-size three-dimensional models of infants with external evidence of disease. The use of these for teaching and research purposes is outlined.

Alginates↗
PubMed1989

Lung surrogates.

In the development and evaluation of mechanical ventilation on the basis of high-frequency oscillation, appropriate surrogates of the lung are important, because they allow the measurement and control of various parameters which are not accessible in animal models. Yet, criteria have to be established according to which results obtained with a surrogate may be assessed with a view to extrapolation to humans. Theoretical considerations and impedance measurements are used for this purpose. It is found that for each given frequency a model can be made which exhibits realistic properties. However, no uniformly valid surrogate in the entire frequency range of 10-50 Hz is available at present.

Animals↗
PubMed2006

Glycine application and right heart function in a porcine heart transplantation model.

Glycine reduces ischemia-reperfusion injury after experimental liver transplantation. We hypothesized that glycine might also protect right heart function in an isovolumic cardiac transplantation model. In six domestic donor pigs 150 ml of a 300 mmol L-glycine solution were administered intravenously. The hearts were then arrested with histidine-tryptophan-ketoglutarate solution. Animals without prior glycine infusion served as controls (n = 6). After 4 h of ischemia, hearts were transplanted into recipients. An isovolumic model was used in which the right ventricular (RV) volume was controlled in vivo using an intracavitary high-compliance balloon. After 1 and 2 h of reperfusion the RV balloon volume was gradually increased and the developed pressures were recorded (P(developed) = P(systolic) - P(diastolic)). Right ventricular failure was defined as a decrease in developed intracavitary pressure. Glycine hearts could be loaded with a significantly increased volume after 1 h (glycine: 53 +/- 13.7 ml vs. control: 32 +/- 11.7 ml; P = 0.015) and after 2 h (67 +/- 18.6 ml vs. 43 +/- 8.2 ml; P = 0.018). Maximal RV developed pressures were not significantly different between groups. Postischemic RV end-diastolic compliance was significantly higher in glycine-treated animals (P = 0.04). Glycine protects early postischemic RV compliance, but has no important influence on maximal developed pressures.

Animals↗
PubMed2006

Gene expression of stretch-activated channels and mechanoelectric feedback in the heart.

1. Mechanoelectric feedback (MEF) in the heart is the process by which mechanical forces on the myocardium can change its electrical properties. Mechanoelectric feedback has been demonstrated in many animal models, ranging from isolated cells, through isolated hearts to whole animals. In humans, MEF has been demonstrated directly in both the atria and the ventricles. It seems likely that MEF provides either the trigger or the substrate for some types of clinically important arrhythmias. 2. Mechanoelectric feedback may arise because of the presence of stretch-sensitive (or mechano-sensitive) ion channels in the cell membrane of the cardiac myocytes. Two types have been demonstrated: (i) a non-specific cation channel (stretch-activated channel (SAC); conductance of approximately 25 pS); and (ii) a potassium channel with a conductance of approximately 100 pS. The gene coding for the SAC has not yet been identified. The gene for the potassium channel is likely to be TREK, a member of the tandem pore potassium channel gene family. We have recorded stretch-sensitive potassium channels in rat isolated myocytes that have the properties of TREK channels expressed in heterologous systems. 3. It has been shown that TREK mRNA is expressed heterogeneously in the rat ventricular wall, with 17-fold more expression in endocardial compared with epicardial cells. This difference is reflected in the TREK currents recorded from endocardial and epicardial cells using whole-cell patch-clamp techniques, although the difference in current density was less pronounced (approximately threefold). Consistent with this, we show here that when the ventricle is stretched by inflation of an intraventricular balloon in a Langendorff perfused rat isolated heart, action potential shortening was more pronounced in the endocardium (30% shortening at 40 mmHg) compared with that in the epicardium (10% shortening at the same pressure). 4. Computer models of the mechanics of the (pig) heart show pronounced spatial variations in strain in the myocardium with large transmural differences (in the left ventricle in particular) and also large differences between the base and apex of the ventricle. 5. The importance of MEF and the non-homogeneous gene expression and strain distribution for arrhythmias is discussed.

Animals↗
PubMed2005

A new automated method for analysis of gated-SPECT images based on a three-dimensional heart shaped model.

A new automated method for quantification of left ventricular function from gated-single photon emission computed tomography (SPECT) images has been developed. The method for quantification of cardiac function (CAFU) is based on a heart shaped model and the active shape algorithm. The model contains statistical information of the variability of left ventricular shape. CAFU was adjusted based on the results from the analysis of five simulated gated-SPECT studies with well defined volumes of the left ventricle. The digital phantom NURBS-based Cardiac-Torso (NCAT) and the Monte-Carlo method SIMIND were used to simulate the studies. Finally CAFU was validated on ten rest studies from patients referred for routine stress/rest myocardial perfusion scintigraphy and compared with Cedar-Sinai quantitative gated-SPECT (QGS), a commercially available program for quantification of gated-SPECT images. The maximal differences between the CAFU estimations and the true left ventricular volumes of the digital phantoms were 11 ml for the end-diastolic volume (EDV), 3 ml for the end-systolic volume (ESV) and 3% for the ejection fraction (EF). The largest differences were seen in the smallest heart. In the patient group the EDV calculated using QGS and CAFU showed good agreement for large hearts and higher CAFU values compared with QGS for the smaller hearts. In the larger hearts, ESV was much larger for QGS than for CAFU both in the phantom and patient studies. In the smallest hearts there was good agreement between QGS and CAFU. The findings of this study indicate that our new automated method for quantification of gated-SPECT images can accurately measure left ventricular volumes and EF.

Artificial Intelligence↗
PubMed1979

A new technique to increase coronary flow. Preliminary report.

This study was planned to investigate whether part of the energy produced by cardiac contraction to propel blood toward the systemic circulation can be used to increase the coronary flow in systole. Ten devices (I-X) designed to divert laterally part of a flow column (without substantially increasing resistance to flow) were tested in a mock circulation and in nine anesthetized dogs. An increase of 11.69 +/- 1.97% (mean +/- SEM, P less than 0.005) in "coronary flow" and of 8.98 +/- 0.56% (mean +/- SEM, P less than 0.001) in coronary sinus flow were obtained with device I mounted on a stylet and placed above the "aortic valve" in the mock circulation and the dogs, respectively, without increasing the flow resistance. The results in;dicate the possibility of diverting part of the aortic flow toward the coronary arteries without increasing mean aortic pressure.

Animals↗
PubMed2004

Simple(r) soft tissue masque for individual fixed restorations.

This article describes a simplified technique for creating a soft tissue masque to aid in shaping the gingival contours of fixed restorations. The additional clinical visit that has been previously described is circumvented, and only one master cast is required.

Dental Impression Technique↗
PubMedDate not supplied

Facial moulage fabrication using a two-stage poly (vinyl siloxane) impression.

Traditional techniques for the fabrication of a facial moulage have relied on materials with various shortcomings. This article describes a two-stage Poly(vinyl siloxane) impression technique that avoids some of these shortcomings and provides a predictable and accurate facial moulage.

Dental Impression Materials↗