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PubMed1980

Inclination of eye-tracking tracing. (A localising parameter in electro-oculography).

A new diagnostic parameter in electro-oculography, viz. 'Inclination of eye-tracking tracing' is presented. Electro-oculographically the pendular eye-tracking tracing was recorded before and after calorization, using the technique of serial thermal vestibulometry. In some cases of brain-stem lesion, the tracing inclined in the direction of the slow component of the calorically-induced nystagmus; but this phenomenon was not noted in cases with peripheral lesions, nor in pure frontal, occipital, parietal of cerebellar lesions. A neuro-anatomical model is postulated in explanation of this phenomenon. It appears that the basic lesion responsible for this phenomenon is a small one partially involving the slow-discharging neuronal units in the lower reticular core and in the adjacent suprasegmental inhibitory cortico-reticular tracts, thus bringing about a state of relative hyperactivity (release phenomenon) of the remaining surviving neurones which belong to the slow-discharging neuronal units. The latter has been referred to here as the 'Inclination Neuronal Mechanism' and this phenomenon appears to be the converse of "Central vestibular recruitment', the former being caused by a lesion in the 'slow-discharging units', the latter by a lesion in the 'quick-discharging units' ('nystagmogenic area'), the two units belonging to the same reticular system but having opposite functions.

Adult↗
PubMed2003

Effect of catheter design on tracheal pressures during tracheal gas insufflation.

BACKGROUND AND OBJECTIVE: This study investigated the distribution of pressures within a model trachea, produced by five different tracheal gas insufflation devices. The aim was to suggest a suitable design of a tracheal gas insufflation device for clinical use. METHODS: Each device was tested using insufflation flow rates of 5 and 10 L min(-1). For each flow rate, the pressure within the tracheal model was measured at 33 fixed points. RESULTS: The Boussignac tracheal tube produced the most even pressure distribution, while a reverse-flow catheter produced pressure changes of the smallest magnitude. CONCLUSIONS: We suggest that catheters producing the lowest pressure changes are likely to be safer for clinical use.

Catheterization↗
PubMed2007

Some observations on the structure and function of the spinning apparatus in the silkworm Bombyx mori.

Silkworm silk has outstanding mechanical properties despite being spun at room temperature and from aqueous solution. Although it has been proposed that fiber formation is mainly induced by shearing and extensional flow in the spinneret, the detailed structure and function of the spinning apparatus of Bombyx mori silkworms are still not fully elucidated. In this paper we describe three aspects of the functional microanatomy of the spinning apparatus: changes in the diameter of the silk gland duct with distance along the duct, how the birefringence of the fibroin changes as it flows down the duct, and the detailed three-dimensional structure of the silk press and related structures. The existence of a double escaped nematic liquid crystal texture in the fibroin in a region of the duct is described. After this region the birefringence suddenly disappeared until the start of an internal draw down taper which commenced just before the silk press. In the internal draw down taper the birefringence increased dramatically to an asymptotic value as a thread was drawn from the fibroin gel. The structure of the silk press suggests that it acts as a restriction die whose diameter can be regulated.

Animals↗
PubMed2004

A radial-basis function based surface Laplacian estimate for a realistic head model.

Scalp surface Laplacian (SL) is widely used to enhance spatial resolution and sensitivity for electroencephalograph (EEG) recordings. In this paper, a radial-basis function (RBF) based surface Laplacian (RBFL) estimate is proposed for realistic head model, in which RBF is used as basis function to interpolate the surface of a head model and the surface potentials. The efficiency of RBFL was confirmed through a comparative study to the global realistic geometry spline Laplacian (GSL) with both simulation studies and human visual evoked potential. The simulations include both feasibility in a 3-concentric sphere head model and influence of head model noise and potential noise, effects of border source and sources separation distance in a realistic head model. All the comparisons show RBFL can provide comparatively better results than GSL and hence RBFL provide another efficient method for high-resolution EEG mapping.

Algorithms↗
PubMed2004

Lectin histochemistry of normal human gastric mucosa.

Information about the saccharides expressed in gastric mucosa is mostly limited to the glycan content of gastric mucins and there are only a few studies of the glycoprofiling of the constituent cells and their components. Knowledge of the glycan expression of normal gastric mucosa is necessary for the interpretation of the significance of changes of expression in disease. lectin histochemical study of normal human gastric (body) mucosa was performed using 27 lectins chosen to probe for a wide range of oligosaccharide sequences within several categories of glycoprotein glycans. here were marked differences in staining reactions in the various microanatomical structures of the mucosa, particularly between pits and glands with the former more closely resembling the surface epithelium. A notable feature was the degree of difference in the staining between a substantial sub-population of cells within the neck region and the epithelium of both the pits and glands. These neck cells resembled the pit cells with some lectins, glandular cells with some others and neither with some other lectins. Overall, the differences between the pit, gland and neck epithelia were diverse and numerous, and could not be explained by altered activity of a small set of glycosyltransferases. Widespread alterations of glycans must have occurred (affecting terminal and internal parts of their structures) and the very different glycotypes of the pit, neck and gland epithelia are, therefore, suggestive of the existence of three cell lineages within normal gastric epithelium.

Cell Lineage↗
PubMed2000

Predetermined implant positioning by means of a novel guide template technique.

This paper presents a novel guide template technique for implant placement. In esthetic implant dentistry with its restoration-driven implant placement as well as in complete-arch cases with multiple implants, the precise positioning and angulation of dental implants is crucial for achieving the desired prosthetic results. Difficulties in implant positioning may arise especially with grafted jaws resulting from communication problems between surgeon and prosthodontist. This method may alleviate some of the problems common to conventional template techniques, where the drill is usually directly guided by the template. The key idea is to fixate the implant position and angulation by the help of Kirschner wires which are inserted in the alveolar ridge right through the mucosa before elevation of a mucoperiosteal flap. Thanks to this sequence, the template for guiding the wires may be positioned precisely, even on grafted edentulous ridges. After the insertion of the wires, the bone is exposed and the implant cavities prepared with a trephine drill guided over the wires alone or over wires combined with a special guidance cylinder fitting the trephine drill. The method may be combined with different planning and radiological techniques. Since the use of the template is detached from the actual drilling process, the danger of introducing debris of plastic or metal into the preparation site may be avoided. The present technique might be helpful for difficult cases by improving communication between prosthodontist and surgeon and also render additional security to the surgeon with less routine in dental implant insertion.

Dental Implantation, Endosseous↗
PubMed2003

Three-dimensional simulation and prediction of craniofacial surgery.

The treatment of patients with complex facial deformities is one of the most challenging multidisciplinary tasks in plastic surgery. Due to advancements in medical technology and surgical techniques in the last 20 years correction of severe malformations has become possible and is performed by highly specialized teams frequently in a single operation. Recent developments in three-dimensional (3-D) imaging techniques have already greatly facilitated diagnosis of complex craniofacial deformities. Computer-based simulation methods for surgical procedures that are based on imaging data have the potential to improve surgical treatment by providing the ability to perform 'virtual surgery' preoperatively and thus reduce patient risk and morbidity intraoperatively. A method is presented for interactive computer-assisted craniofacial plastic surgery planning and visualization, especially simulation of soft tissue changes using an experimental Craniofacial Surgery Planner. The system computes non-linear soft-tissue deformation because of bone realignment. It is capable of simulating bone cutting and bone realignment with integrated interactive collision detection. Furthermore, soft-tissue deformation and cutting due to surgical instruments can be visualized. Simulation processes are based on an individual patient's preoperative 3-D computed tomography and on a 3-D, photo-realistic model of the patient's preoperative appearance obtained by a laser range scanner. Very fast and robust prediction of non-linear soft-tissue deformation is computed by optimizing a non-linear cost function.

Computer Simulation↗
PubMed2003

Video reconstructions in dentistry.

OBJECTIVES: To present two practical techniques for three-dimensional (3D) modeling of the human jaw from a sequence of intra-oral images. DESIGN: A data acquisition system consists of: 3D digitizing arm, CCD camera and a laser projector in addition to a software module of two 3D modeling techniques; shape from shading (SFS) and space carving (SC). SETTING AND SAMPLE POPULATION: Several experiments have been conducted on a sample of students at the Computer Vision and Image Processing (CVIP) Laboratory at the University of Louisville, Louisville, KY. Other experiments were performed on solid models of human jaw. EXPERIMENTAL VARIABLE: The SFS technique, using perspective projection and camera calibration, extracts the 3D information from a sequence of two-dimensional images of the jaw. Data fusion of range data and 3D registration techniques develop the complete jaw model. The SC approach is implemented on a sequence of calibrated images. On the two reconstructions, we fit a mesh model to the data, in order to create a solid 3D model. OUTCOME MEASURE: The accuracy of the reconstructed 3D model of human jaw is calculated based on the measurements on real jaws. RESULTS: The SFS-based technique seems to provide more faithful information about the shape of the tooth tops. However, the SC algorithm successfully reconstructed 3D models of the human jaw with sub-millimeter accuracy, which is as accurate as (or even better than) the first technique without using any range measurements or laser projectors. The average error in distance calculation was found to be 0.74 mm, which is an acceptable resolution for many orthodontics and maxillofacial applications. CONCLUSION: Accurate 3D reconstruction of the human jaw enables many orthodontics and dental imaging research findings to be applied directly to a digital jaw model--not to a cast--using computer vision and medical imaging tools.

Algorithms↗
PubMed2001

Irregularity skin index (ISI): a tool to evaluate skin surface texture.

BACKGROUND/AIMS: Irregularity of skin surface microtopography is difficult to evaluate in Euclidean geometry. Using a fast Fourier transform (FFT), it is possible to convert a space field into a frequency field and to obtain quantitative evaluation of this important feature of the skin. The aim of the present study was to test the applicability of a new parameter, derived from computer assisted FFT, to skin texture, in order to quantify its irregularity. This parameter has the additional advantage of being anisotropic. METHOD: The study was conducted on 50 female volunteers. Skin replicas were performed on a healthy area that was not chronically photo-exposed. A new parameter, called "irregularity skin index" (ISI), was identified from FFT. The correlation with volunteers' age was calculated. RESULTS: ISI was calculated by FFT in two different directions (referred to the x and y axis of the diagram of the FFT and named, respectively, ISIomegax and ISIomegay). The irregularity skin indexes increased with age of the subjects, showing a correlation with age of r=0.47 (ISIomegax) and r=0.51 (ISIomegay). CONCLUSION: By showing a relatively good correlation with age, ISI seems to be a promising parameter for the study of ageing skin.

Adult↗
PubMed2001

Scale-sensitive fractal analysis using the patchwork method for the assessment of skin roughness.

BACKGROUND/AIMS: As skin roughness and wrinkles are easily perceived by the consumer, quantifying skin surface structures is a vital parameter for cosmetic product development. As more tools are available for measuring three-dimensional (3-D) surface data, instead of two-dimensional (2-D) profile lines, new algorithms are desirable, to take advantage of the information gathered. METHODS: The patchwork method tiles topographic data sets virtually and analyzes the change in apparent area as a function of tile scale. The patchwork method and conventional 2-D profilometric analysis were applied to 24 topographic skin data sets. The data sets were derived before and after application of 15% glycerol solution on the skin of eight volunteers. RESULTS: One hour after application, skin roughness decreased by 20.8%, as measured by conventional analysis, and by 23.3%, as measured by the patchwork method. For both methods, the differences were not significant. CONCLUSIONS: The patchwork method can be applied to skin data and renders results similar in intensity and direction to conventional 2-D analysis. It is advantageous over conventional 2-D analysis in three ways: it makes use of the full topologic information, it requires no high-pass or low-pass filtering, and it is independent of the anisotropy of the skin.

Algorithms↗
PubMed1998

Glutamate locally activates dendritic outputs of thalamic interneurons.

The relay of information through thalamus to cortex is dynamically gated, as illustrated by the retinogeniculocortical pathway. Important to this is the inhibitory interneuron in the lateral geniculate nucleus (LGN). For the typical neuron, synaptic information arrives through postsynaptic dendrites and is transmitted by axon terminals. However, the typical thalamic interneuron, in addition to conventional axonal outputs, has distal dendrites that serve both pre- and postsynaptic roles. These dendritic terminals participate in curious and enigmatic triadic arrangements, in which each contacts a relay cell dendrite and is contacted by a glutamatergic retinal terminal that innervates the same relay cell dendrite. Here we show that agonists of the metabotropic glutamate receptor (mGluR) activate dendritic terminals of interneurons in the absence of action potentials, thereby inhibiting the postsynaptic relay neuron. Somatic recordings from LGN interneurons reveal that there is no response to mGluR agonists, suggesting that their dendritic terminals are electrically isolated from their somata and axons, consistent with anatomical modelling of these cells. Our results offer insight into the functioning of triadic circuitry and indicate that thalamic interneurons can perform independent computations expressed through axonal as opposed to dendritic outputs.

Animals↗
PubMed2004

An optimal bronchial tree may be dangerous.

The geometry and dimensions of branched structures such as blood vessels or airways are important factors in determining the efficiency of physiological processes. It has been shown that fractal trees can be space filling and can ensure minimal dissipation. The bronchial tree of most mammalian lungs is a good example of an efficient distribution system with an approximate fractal structure. Here we present a study of the compatibility between physical optimization and physiological robustness in the design of the human bronchial tree. We show that this physical optimization is critical in the sense that small variations in the geometry can induce very large variations in the net air flux. Maximum physical efficiency therefore cannot be a sufficient criterion for the physiological design of bronchial trees. Rather, the design of bronchial trees must be provided with a safety factor and the capacity for regulating airway calibre. Paradoxically, our results suggest that bronchial malfunction related to asthma is a necessary consequence of the optimized efficiency of the tree structure.

Asthma↗
PubMed2003

Not too big, not too small: the appropriate scale.

The tools we use at the human scale, whether mechanical, medical or microelectronic, depend on materials for which some other scale of length or time is critical. Often this is the mesoscale, between the scales of engineering and of atomic science. Linking underlying processes to what we handle is sometimes called 'spanning' (or 'bridging') length scales, giving the impression that the mesoscale is a swamp to be crossed without getting mud on our boots. This is misleading: we do not wish to span the mesoscale, but to work at the appropriate scale, and to connect that to our human needs. The appropriate scale need not rule out multiscale computer modelling, in which some supercode integrates relevant scales in one pass, hoping to combine the best of methods for two or more levels. But the reality for such attempts, too often, is that the worst of both regimes are found. Happily, simpler strategies at a judicious scale will often suffice.

Bone and Bones↗