Computer simulation for teaching endoscopic procedures.
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Computer Graphics↗
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Teaching by endoscopy simulation.
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Computer Graphics↗
[3-dimensional organ image using ultrasound].
This is the first report in literature on three-dimensional imaging of organs via sonography. The relevant experiments were performed in vitro. Whereas MRI and CT can produce three-dimensional images of bodies by means of appropriate computer programmes, we had to search for special techniques in sonography that would communicate to the computer the exact positioning and arrangement of the individual segments to be reconstructed to supply a three-dimensional image. In MRI and CT the individual segments are arranged parallel to one another; the distance between the individual segments is known; all the computer has to do is to add up these segments to produce a spatial image. In contrast to this, conventional sonography cannot supply parallel segments or sections due to the unevenness of the human skin. Hence, it was not possible to use the computer programmes compiled for the three-dimensional reconstruction of MRI and CT images, in sonography; special transducer guides had to be constructed before this could be realised. One of our special constructions enabled parallel shifting of the transducer to obtain parallel segments or sections, and another construction enabled rotation of the transducer to obtain segments or sections differing from one another by a known angle of displacement. In this manner the computer was able to reconstruct an organ to supply a three-dimensional image--a first-time achievement. Using these devices, we examined a kidney in a water-bath. By means of outlining of the individual sonographic segments, only their surfaces are depicted, and these are reconstructed to produce a three-dimensional body by means of newly developed computer programmes.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
[3-dimensional ultrasound image of the infant hip].
Clinical and experimental studies proved the usefulness of three-dimensional sonographic diagnosis by means of a newly constructed transducer providing for a coordinated sequence of cuts, and hence initial trials investigated its application in sonographic diagnosis of the infant hip. Differences were found in the three-dimensional anatomic image between normal and dysplastic hips. It is no longer necessary to draw any lines or to perform any calculations of angles as required in "conventional" hip sonography. In contrast to conventional hip sonography, the use of a sector transducer is meaningful with this method, since the drawbacks of the sector transducer stated by Graf, do not apply. Clinical studies will have to confirm the possible use of this new method in diagnosis disturbances in infant hip maturation.
Computer Graphics↗
[A new procedure for 3-dimensional reconstruction of the surface of the tongue from ultrasound images].
A new method for 3D-surface-reconstruction from coronary ultrasound images is presented using 3D-data of a prototype volume scanner. In addition to conventional morphological and functional diagnosis of the tongue, 3D-surface-reconstruction provides remarkable information on the tongue surface, especially during articulation.
Algorithms↗
[Computer-assisted evaluation of ultrasonically obtained biometric data in pregnancy].
Sonographic supervision of the baby's growth is an important technique in obstetrics in order to recognise foetal diseases at an early stage. A computer programme was designed to simplify analysis and classification of these data. The results show that computer analysis is more objective, less biased and simpler than the manual method.
Biometry↗
[Three-dimensional ultrasonic diagnosis in gynecology and obstetrics].
Three-dimensional reconstruction of an organ requires a coordinated sequence of cross-sectional scans. In ultrasound this can be solved by rotating the scan plane horizontally or vertically. Two scan heads have been built, one to rotate the plane around a horizontal, the second around a vertical axis. There are two ways to reconstruct the scans taken by ultrasound into a three-dimensional image: --to contour the surface of the organ in each scan and to reconstruct these contours to a ring-shaped structure. This procedure needs a lot of time; moreover, contouring must be performed via cursor on the screen. --calculate a transparent image of the organ. To obtain the best spatial image by the "transparent method", the image must be moved on the screen. Both methods of reconstruction are shown and compared in this paper. First experiences show that they can be applied in tumour diagnostic and in the diagnosis of malformations in early pregnancy. Further clinical studies will have to prove this.
Breast Neoplasms↗
[Treadmill versus field trial. Movement analysis and pressure distribution in the athletic shoe].
Our current knowledge on interactions between runner and runningshoe is mainly based on treadmill measurements. In order to reveal stress load and adaptation on playing surfaces it was necessary to develop a combined measuring device out of 3-D video motion analysis and portable pressure measurement system. By means of a motor driven cart moving parallel to the subject with comparable position of cameras to the treadmill test it was possible to set up an identical trial for track and field. 12 subjects (male, age 24-32, size 9) were tested at a speed of 2.8 m/s. The varying conditions were treadmill and grass and two different constructed running shoes. 200 cycles and over 1000 steps were analyzed. The quantitative analysis of 37 parameters describing the contact phase was performed using the wilcoxon test for paired samples.-A qualitative comparison of running styles was introduced by using angle-angle-diagrams (knee and ankle by 3-D data) similar to those first described for 2-D by P.R. Cavanagh in 1973. It showed a huge interindividual variability under same conditions. Comparing the angle-angle-diagrams for the four different running conditions it was possible to classify them into three characteristic groups: non-adaptors, surface-adaptors and shoe-adaptors. Comparing track and field to treadmill measurements significant differences were found for the knee at impact: On treadmill the initial knee angle was 4.6 degrees more extended at a 13% higher angle velocity and a 30% higher angle deceleration (sig. p less than 0.05). A 7.3% higher impulse was found on grass at a 5.9% higher step length. No difference in maximum pressure was found. These results show that adaptation is performed mainly by the knee. Changing the motion pattern the knee seems to be capable of homogenizing the different stress loads to the foot. Comparing the running shoes significant differences were found in the motion of the ankle: a controversial behaviour was found to be on treadmill and grass. The pressure data revealed significant differences for the treadmill test to be in the heel area, for grass in the arch area. This points to an--up to now--unknown importance of the arch on unplain surfaces that are obviously influenced by the construction of the shoe and are not accessible by treadmill tests. The described different behaviour of shoes in treadmill and track and field tests points out the reduced validity of single treadmill tests.(ABSTRACT TRUNCATED AT 400 WORDS)
Adult↗
[Ski shoe versus knee joint--3: Risk for falling backward].
In contrast to the drop in the incidence of fractures of the lower leg that has been observed in recent years, the incidence of knee injuries has not decreased in skiing. There has even been a relative increase of severe knee lesions and isolated ACL ruptures, prompting us to conduct a comprehensive study of the causes of this phenomena. The goal of the study was to develop a new measuring device for alpine skiing research by combining motion analysis, pressure and force measurement, comprehensive examine the forward/backward movement in skiboots in the lab and by means of telemetry on the slope (Skiboot versus knee joint part 1/Sportverlerletzung. Sportschaden 3, 1989, pp. 149-161) and to come up with a proposal for a new safety concept to reduce the high number of knee injuries in alpine skiing in the future. The first study was devoted to the forward movement in skiboots (Skiboot versus knee joint part 2/Sportverletzung. Sportschaden 4, 1990, pp. 1-13). The results showed that a skiing style in backward lean position was adopted by skiers wearing boots with a stiff forward flexion and was supported by the fixed backward spoiler. In order to quantify the influence of the backward spoiler a special skiboot was constructed allowing the rear spoiler to give way at a variable, defined stiffness and register the angular displacement and horizontal force Fh. The results showed most clearly that even a medium rear spoiler resistance will sign, reduce the peak force values by a factor of 5.5. The acceleration at the knee joint level is significantly higher (factor 1.6, p less than 0.05) in case of a rigid spoiler. The lab tests could be confirmed on the slope (sign. reduction of max. force by factor 8). It also proved that normal skiing can be performed in such a boot without limitations. In consideration of our facts it is concluded that the principle of safety bindings must definitely apply in future in equal measure also to the ski boot. As a proposal for future safety ski boot, that allowed for the first time the rear part to give way after a certain amount of force (adjustable preload). The backward release bindings, which can often produce dangerous malfunctions if a strong force acts on them for a short period of time, could thus be complemented by a safety system in the boots. In all probability this would be a contributing factor to reducing the high incidence of knee injuries in skiing.
Adult↗
[Imaging time-dependent changes in the nasal mucosa using the most modern morphing software].
Changes in the nasal mucous membrane lasting longer than 1-2 minutes have, until now, escaped dynamic observation. Even the congestion and decongestion of the turbinates during the nasal cycle and after application of vasoconstrictive nose drops have been documented only by instant stills. For this reason, we developed a method which permits documenting time-dependent endonasal mucosal changes with their natural dynamics on time-lapse video film. Instead of primarily recording a continuous video film, we processed instant stills. Computer interpolation of intermediate steps gives the viewer a dynamic impression. As continuous video endoscopy is not feasible, we produced the continuous film by recording video sequences of approximately 30 seconds length in defined time intervals endoscopically, selecting single stills (so-called original photographs) from each sequence, and splicing them, producing the missing intermediate photographs by a special computer technique (morphing), similar to mathematical interpolation. In this way we could demonstrate the changes of the right and left inferior turbinate during a nasal cycle of lasting five hours and the effect of xylometazolin nose drops on the nasal mucosa. The practical value of this technique, lies in the comprehensive realistic observation of dynamic processes of the nasal mucosa with respect to physiology and pathophysiology.
Adult↗
[Color vision in relation to age: a study of normal values].
BACKGROUND: It is difficult to quantify thresholds in most colour vision tests, and this is especially the case for tritan hues, where a strong age-related increase of threshold has been reported. With the development of computer-graphic methods it is possible to remove brightness clues caused by lens absorption. This study attempts to give normative values for colour contrast thresholds and assess the age related changes therein. PATIENTS AND METHODS: 115 patients aged between 6 & 71 years were tested for central and peripheral colour contrast sensitivity. No patient had any systemic or eye disease. As a preliminary, heterochromatic flicker balance between the luminosities of the R and G and B and G phosphors was established, so that all colours subsequently generated were isoluminant for the person tested. Then, using a modified binary search technique, colour contrast thresholds were established using both 2 degree optotypes, for central vision, and a ring, 12.5 degrees in radius for peripheral vision. In the latter case, the observer had to name the position of the missing quadrant in the ring. Stimuli were presented for 200 msec at 1 Hz. Colours were modulated on protan, deutan or tritan colour axis. RESULTS: No correlation between age and central colour vision thresholds was observed. By contrast a significant but only minor increase of peripheral colour vision threshold was observed for the peripheral protan and tritan axis. DISCUSSION: The present system removes luminance clues from colour vision tests and permits both central and peripheral retina to be tested. The results are simple in that the influence of age can be neglected. The variability of threshold results is small, and it is easy to detect the relatively large changes associated with disease. Since high-quality monitors are standardised and calibrated, providing the stimulus parameters described are adhered to, the results given here for upper limits of normal may be used for other similar systems.
Adolescent↗
[The distribution of cartilage degeneration of the human patella in relation to individual subchondral mineralization].
According to Pauwels and Kummer the distribution of the subchondral mineralisation can be taken as a measure of the long-term mechanical loading in the joints. Based on a previous study concerning the density distribution of the subchondral bone of the human patella, these results were compared in the following paper with the macroscopically visible cartilage lesions. Degenerative changes on the lateral facet of the patella coincide with regions of high bone mineralisation, those on the "odd facet" on the other hand with areas of low subchondral density. The cartilage lesions on the lateral facet are seen as being due to high and constant mechanical stress, those on the "odd facet" to short infrequent stress-peaks.
Absorptiometry, Photon↗
[A new white-noise campimeter].
In this prototype white-noise field is now generated on a high definition adjustable 19" colour monitor. With the help of a "touch-screen" the patient can draw the borders of his scotoma himself. As the white-noise stimulus is produced by software, there is a much greater variability of white-noise field specifications (brightness, intensity of noise, colour, ...). Furthermore, these parameters can be changed exclusively in circumscribed parts of the noise field (e.g. in a scotoma area). By that way a simulation or even a quantification of perceived noise field defects can be realized. Fixation is controlled with the help of an IR video camera. Input and storage of data as well as their presentation and output (on a Laserwriter) have been substantially improved.
Computer Graphics↗
[Evaluating visual function with visual display graphics on the Macintosh II computer].
A collection of programs has been developed on the Macintosh II computer to generate visual tests for an ophthalmological practice. The large number of available colours makes it possible to emulate most of the available tests and also to develop new ones. The system allows testing of the following visual functions: Visual acuity, Stereopsis, Aniseikonia, Phoria, Cyclophoria, Colour Vision and Contrast sensitivity.
Color Perception Tests↗
[Distortion of progressive addition lenses and its physiologic evaluation].
The distortion of progressive addition lenses is one of the important criteria for the amicability of the lenses for the patient. A method to calculate the distortion for the using situation is shown and the application for three lens types demonstrated.
Computer Graphics↗
A New Technique for CT/MR Fusion For Skull Base Imaging.
This paper presents our initial experience utilizing a new technique which allows CT and MR image fusion in patients with skull base lesions. Eleven patients with a variety of skull base lesions underwent CT and MR imaging prior to surgery. Both sets of images were coregistered using customized software. The CT and MR data sets were then combined and viewed in a single interactive image formar using a high-speed graphic computing system. Image fusion allowed simultaneous visualization of the bony skull base anatomy (CT) and detailed soft tissue anatomy (MR) using a single image format. Combining both modalities was felt to provide a better assessment of the extent of lesions and improve understanding of their relationship to adjacent bony and neurovascular anatomy. Specifically, image fusion enhanced awareness of location of skill base lesions with respect to the cavernous sinuses. Gasserian ganglia, carotid arteries, and jugular foramina. For tumors arising within the internal auditory canal (IAC), fused images allowed better delineation of the lateral aspect of the lesion with respect to the fundus of the IAC. Thus, fusion of CT and MR studies provides a unique image format which has advantages over single modality display. We believe image fusion is beneficial for surgical planning and for treatment planning of complex skull base malignancies treated with radiotherapy.
Journal Article↗
Parameter dependence of stochastic layers in a quasicrystalline web.
Stochastic web maps with approximate quasicrystalline symmetry possess an infinite number of inequivalent fixed points embedded in stochastic layers of varying thickness. In this investigation exploratory steps are taken toward a systematic numerical determination of the widths of the stochastic layers as a function of the web map's control parameter. The study concentrates on a particular stochastic layer in the approximately fivefold symmetric web. Computer graphics and a simple stretching-and-folding criterion provide a coarse view, which is supplemented at finer scales by Greene's residue method. The exact reflection symmetries of invariant sets, as well as a five-dimensional representation of the map, are exploited to improve numerical precision. As the control parameter varies, one finds not only variations expected from island chain structures, but also larger-scale oscillations whose origin is not understood.
Journal Article↗
Stochastic webs and continuum percolation in quasiperiodic media.
We report the results of an analytical and numerical study of the contour line and surface geometry in two models of continuum percolation with quasiperiodic properties. Both the fractal dimension of long isolines and the scaling coefficient nu are determined analytically for the two-dimensional percolation problem. The scaling characteristics of the isosurfaces of the three-dimensional potential function with an icosahedral symmetry are obtained using computer graphic representation.
Journal Article↗