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Results for “Photogrammetry”

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At least 109 records · Page 6Linked to original sources

PubMed1977

Comparative reproducibility of the digital photogrammetric procedure utilizing three methods of stereophotography.

The reproducibility of digital photogrammetry of optic nervehead photographs taken with the Zeiss fundus camera with Allen stereoseparator, the Donaldson fundus camera, and the Zeiss fundus camera with twin-prism separator were evaluated. Reproducibility of the various quantitative factors was significantly better when the two types of simultantic cups. Larger per cent errors were encountered with shallower optic cups. Substantial improvements in parameter reproducibility were obtained when finer sampling intervals were used during film digitization.

Computers↗

PubMed2026

Effect of Global Postural Re-Education in Individuals With Text Neck Syndrome: A Randomized Controlled Trial.

BACKGROUND AND PURPOSE: This study investigated the effect of Global Postural Re-Education (GPR) versus conventional physical therapy in text neck syndrome (TNS). A prospective, single-blinded, parallel-group randomized controlled trial design was used. METHODS: Sixty participants with TNS (aged 18-40 years) were randomly assigned to either conventional treatment or GPR plus conventional treatment. Both groups received supervised therapy for three sessions per week over 4 weeks. Outcome measures included craniovertebral and shoulder angles assessed by photogrammetry, pain intensity via Visual Analog Scale, and Cervical Range of Motion via a smartphone application (Clinometer). Measured before and after the intervention. RESULTS: Within-group analyses showed significant improvements in pain and CROM in both groups (p < 0.001). However, the between-group analysis revealed no superiority of GPR for pain or CROM (p > 0.05). In contrast, GPR demonstrated statistically significant superiority in postural correction, with greater improvements in craniovertebral angle (MD: 2.14°; 95% CI: 0.69-3.59; p = 0.005) and shoulder angle (MD: 3.2°; 95% CI: 0.33-6.07; p = 0.03), exceeding MCID thresholds and indicating clinically meaningful benefits. However, these findings should be interpreted with caution because of the longer session duration in the GPR group. DISCUSSION: Incorporating Global Postural Reeducation (GPR) into conventional treatment provided significant additional benefits for postural parameters (craniovertebral and shoulder angles) in individuals with text neck syndrome. However, GPR demonstrated no added superiority over conventional treatment alone regarding pain intensity and cervical range of motion outcomes.

Humans↗

PubMed1983

An approach to the functional anatomy of the sacroiliac joints in vivo.

This first part of this paper is a review of the literature on the functional anatomy of the sacroiliac joint followed by a preliminary biomechanical study of the fresh post mortem pelvis. The latter was done in order to determine the coefficients of the screw matrix and the position of the instantaneous centers of rotation during the symmetrical movements of nutation and contranutation simulated in the biomechanics laboratory. The main part of this work deals with the spatial analysis in vivo of the relative displacements of the iliac bones with respect to the sacrum in the course of dissymmetrical movements of the pelvis. In the different phases of movement, the roentgenographic observation of the position of the bony components with respect to a three-dimensional orthonormal reference system required the use of material based on the principles of photogrammetry. This technique was used to achieve spatial reconstruction of the data recovered from a series of orthogonal x-ray films of the sacroiliac joints. Data retrieval was carried out on a digital table linked to a computer with a graphic terminal so that the information could be displayed in the form of rectangular coordinates of defined points on the bone. Owing to the limited amplitude of articular displacement, a statistical study was required to retrieve the coordinates from the projection of these points on the X-ray film with an estimated threshold of significance of 0.1 and an error of +/- 0.1 mm.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1990

The relative merits of direct morphometry of reconstructions of whole cells, and statistical morphometry by stereology of random sections of cells.

Stereology, or the derivation of quantitative, three-dimensional (3-D) data about cells by statistical analysis of the structures of random sections, is widely used in cytology and pathology. However, there are situations where this approach is inadequate, and only an analysis of a homogeneous population of whole cells will give the required results. This involved 3-D reconstruction from physical or optical sections, or tomography or photogrammetry of whole-cell mounts. Use of stereo views of individual sections or projections adds considerably to the information available for both contouring and reconstruction. Recent image-processing advances in clinical radiography have shown, for the first time, that rapid, high-resolution digitization and contrast enhancement enable nearly all structural details to be routinely extracted from the micrographs and adequately portrayed. Three-D whole-cell reconstructions provide the digital data for many kinds of morphometric measurements on both whole cells and their individual organelles and membranes. Rapid fixation or freezing allows improved quantitative structure/function correlations of organelles with disturbances in cell metabolism or gene expression.

Animals↗

PubMed1989

An experimental setup for the measurement of forces on a human cadaveric foot during inversion.

An experimental setup was developed for statically measuring seven vertical and three horizontal reaction forces on the foot. In the setup, the leg can be simultaneously loaded (1) by a vertical force, (2) by an externally applied axial moment, and (3) by simulated muscle forces. The foot is free to invert under influence of the external loads. Statical analysis and test experiments were used for evaluation. The setup can be used in combination with Roentgen photogrammetry to measure bone positions simultaneously with forces.

Cadaver↗

PubMed1993

Stereotactically guided fractionated radiotherapy: technical aspects.

A system for high precision radiotherapy in the head and neck region has been developed. The components of the system are a head mask connected to a stereotactic frame, a localization unit that can be used during CT- and MR-imaging and a stereotactic target positioner. Conformal precision radiotherapy is planned with a new treatment planning system (Voxelplan-Heidelberg). Three different multi-leaf collimator systems are used. An evaluation of the precision and accuracy of the head fixation system, which was performed with a photogrammetry system, is presented.

Head↗

PubMed1985

A photogrammetric method to measure fluid movement across isolated frog retinal pigment epithelium.

Bullfrog retinal pigment epithelium (RPE)/choroid explants were mounted in an Ussing chamber modified so that the side bathing the choroid was completely sealed. Net fluid movement across the RPE and into or out of the sealed side of the chamber forced the tissue to assume a convex or concave shape. Photogrammetry was used to measure this tissue bowing by analyzing the displacement of the image produced on the RPE surface by an off-axis laser. Under baseline conditions, measured net fluid movements were always in the retina-to-choroid direction with a mean of 7.6 microliter cm-2 h-1. Potential artifacts from a variety of sources have been examined and shown to be insignificant.

Animals↗

PubMed1985

Measurements of reversibility of optic disc cupping and pallor in ocular hypertension and glaucoma.

Four cases are presented of young and elderly glaucoma patients who had both surgical and medical therapy and showed reversal of cupping and pallor of the optic disc. The cupping was measured by photogrammetry and the pallor by computerized image analysis from photographs of the optic disc. Two patients showed regression of visual field loss. The optic disc and visual field changes corresponded to the changes in ocular pressures, generally showing worsening with an increase in ocular pressure. With a decrease in ocular pressure there was regression of visual field loss and a decrease in cupping; pallor did not decrease consistently. The changes in cupping and pallor in some patients followed similar courses but in others behaved in an independent manner. It is proposed that these new sensitive and reproducible techniques for measuring changes in the optic disc may allow the detection of disc changes early in the disease, prior to visual field loss. If treatment is begun at this time, reversal of optic disc changes may occur.

Aged↗

PubMed1975

A transverse loading system applied to a modified Harrington instrumentation.

Observations using standard Harrington Instrumentation revealed that while maximal distractive forces are applied it is possible to produce further correction of spinal deformity by applying a lateral force. Modifications to the standard Harrington Instrumentation by applying a transverse loading system have been made in order to produce this added correction. The transverse load is applied as nearly as possible in the same plane as the bearing points of hooks, i.e., below the axis of the rods. Transverse loading helps to reduce the distance from the apex of the curve to the midline, thereby producing a more stable spine as well as providing additional support on the convex side. The system is ideal for flexible curves with little kyphosis. Photogrammetry reveals that there was no significant rotation occurring after the application of the transverse load. To date, Instrumentation has been used in 10 patients with success.

Adolescent↗

PubMed1992

The computer synthesis of expressive faces.

This paper presents a methodology for the computer synthesis of realistic faces capable of expressive articulations. A sophisticated three-dimensional model of the human face is developed that incorporates a physical model of facial tissue with an anatomical model of facial muscles. The tissue and muscle models are generic, in that their structures are independent of specific facial geometries. To synthesize specific faces, these models are automatically mapped onto geometrically accurate polygonal facial representations constructed by photogrammetry of stereo facial images or by non-uniform meshing of detailed facial topographies acquired by using range sensors. The methodology offers superior realism by utilizing physical modelling to emulate complex tissue deformations in response to coordinated facial muscle activity. To provide realistic muscle actions to the face model, a performance driven animation technique is developed which estimates the dynamic contractions of a performer's facial muscles from video imagery.

Computer Graphics↗

PubMed1976

The effect of oral physiotherapy on dilantin gingival hyperplasia.

Gingival hyperplasia was studied in 13 boys with epilepsy living in a state hospital. Boys were selected on the basis of having gingival hyperplasia, having all teeth between cuspids (upper and lower), having no occlusal abnormality and being cooperative. After gingivectomy, regrowth of gingiva was compared around lateral incisors on one side of the mouth having operator-assisted oral hygiene with that around lateral incisors on the other side of the mouth without operator-assisted oral hygiene. Regrowth of tissue was documented by precise photogrammetry. Oral hygiene, gingival inflammation and crevicular fluid were monitored. Less inflammation, less crevicular fluid and less regrowth of gingival tissues occurred around teeth subjected to good oral hygiene. Precise periodic photographic documentation of the clinical status of patients during studies such as this is considered very valuable.

Adolescent↗

PubMedDate not supplied

The PAR Technology Corneal Topography System.

BACKGROUND: Computer-assisted videokeratography has emerged as a useful clinical and research tool. All of the currently available commercial units utilize a modified placido disk image and require a smooth reflective surface. The PAR Technology Corneal Topography System (PAR CTS) is a prototype of a new computer-assisted corneal imaging device. The system produces a true topographic map (elevation map) by analyzing a projected grid on the corneal surface, as opposed to a placido disk reflection, and utilizes the technique of raster photogrammetry to define elevation points on the corneal surface. Because the system defines elevation points, not curvature, mathematical modeling is easily accomplished. Current software displays include a true topographic map, a spherical subtraction map in both relative and absolute scales, and a meridian analysis that is adapted to display refractive photoablative surgery. METHODS: We evaluated the accuracy of this device by analyzing three calibrated test spheres (55.76, 42.21, and 33.55 diopters). The test spheres were steel balls coated with a thin white silicone polyester coating that was necessary for grid projection. The test spheres were measured by a Taylor-Hobson contact profilometer possessing submicron accuracy. To determine the reproducibility of the system, three investigators measured three noncalibrated balls (20 mm, 18 mm, and 12 mm). The optical system was purposely decentered and refocused after each reading. RESULTS: Utilizing the CTS custom optics, system accuracy at the 8-millimeter test area was 0.03 (SD 0.03), 0.00, (SD 0.02), and 0.07 (SD 0.01) D respectively. Smaller diameter test areas resulted in a predicted loss of accuracy. Maximum intraobserver variability was 0.09, 0.06, and 0.11 D respectively, and maximum interobserver variability measured 0.18, 0.12, and 0.16 D. CONCLUSIONS: These data demonstrate that the PAR CTS is both highly accurate and reproducible in determining topography of spheres that approximate the curvature of the human cornea.

Algorithms↗

PubMedDate not supplied

Wear measurements in clinical studies of composite resin restorations in the posterior region: a review.

During the last twenty years, wear-evaluation methods have changed, with newer techniques developed to determine the extent of loss of material in posterior composite resin restorations functioning in the mouth. These included: direct clinical evaluation; marginal evaluation on models; heights of exposed cavity walls; volumetric assessment of impressions; profilometry and artificial or natural references; section measurements; coordinate measuring device, contact and noncontact scanning; measuring microscope; photogrammetry; moiré topography; laser interferometry; scanning electron microscopy; and optical scanning. A laser scanning technique appears to hold great potential in clinical research.

Bicuspid↗

PubMed1990

Breast form changes resulting from a certain brassière.

Eleven adult female subjects aged 22-39 years wore a certain brassière for 3 months while anthropometry and moiré fringe photographs on the anterior trunk were taken regularly once a week. After the 3 months, the brassière was not worn for another 3 months. Then the measurements and photogrammetry were repeated for comparison using superimposed moiré configurations. The results are summarized as follows. Regardless of slim or obese trunk, subjects with pendent breasts showed the highest degree of breast form "correction" from wearing the brassière. In all subjects, after 3 months of brassière constraint, the underbust circumference was smaller but the chest circumference became enlarged, the distance between the right and left nipples became wider, and the breasts tended to hang down. This change was more marked in obese subjects with pendent breasts. And when this type of subject wore a "well-fitted" brassière for a long time, her breast form became developed; that is, her breasts hung down more.

Adaptation, Physiological↗

PubMed1990

[The spread of the backspray under different working conditions].

The use of high- and highest-speed preparation instruments and the therefore required intensive spray cooling results not only in more efficient working possibilities but also in an increased infection hazard, especially for the dentist and his assistance caused by the spray rebound. Simulated preparations were carried out on different tooth surfaces at different positions of the patient with or without exhaust under clinical conditions to objectify the space spreading of the spray rebound. The arrangement of the equipment has been objectified by photogrammetry so that the measurement data could be clearly classified. The use of the spraying mist exhaust reduces the spray rebound between 50 and 65%.

Aerosols↗

PubMed1989

[Dynamic study of the optic papilla].

There are several methods of accurately measuring the contours of the papilla and rim. Of these methods, photogrammetry and its refinements are known to provide reproducible results. Unfortunately, there is a discrepancy between the accuracy of these methods and the biological "background noise". This noise does not allow the precision of these methods to be improved beyond a certain level. This also applies for determination of the color of the papilla. An alternative to this problem is to use the "provocation" test. In this article, we try to show the importance of the dynamic test of the papilla (dynamic provoked circulatory response): measuring the change in pallor of the rim during an artificial increase in the intraocular pressure.

Glaucoma↗

PubMed1989

New methods for quantitative and qualitative facial studies: an overview.

The clinical study of birth defects has traditionally followed the Gestalt approach, with a trend, in recent years, toward more objective delineation. Data collection, however, has been largely restricted to measurements from X-rays and anthropometry. In other fields, new techniques are being applied that capitalize on the use of modern computer technology. One such technique is that of remote sensing, of which photogrammetry is a branch. Cartographers, surveyors and engineers, using specially designed cameras, have applied geometrical techniques to locate points on an object precisely. These techniques, in their long-range application, have become part of our industrial technology and have assumed great importance with the development of satellite-borne surveillance systems. The close-range application of similar techniques has the potential for extremely accurate clinical measurement. We are currently evaluating the application of remote sensing to facial measurement using three conventional 35 mm still cameras. The subject is photographed in front of a carefully measured grid, and digitization is then carried out on 35-mm slides specific landmarks on the cranioface are identified, along with points on the background grid and the four corners of the slide frame, and are registered as xy coordinates by a digitizer. These coordinates are then converted into precise locations in object space. The technique is capable of producing measurements to within 1/100th of an inch. We suggest that remote sensing methods such as this may well be of great value in the study of congenital malformations.

Cephalometry↗

PubMed1989

Facial morphology as determined by anthropometry: keeping it simple.

Anthropometry remains an efficient, noninvasive method for describing craniofacial morphology in spite of the appearance of more sophisticated technologies. The major advantage afforded by anthropometry is its technical simplicity, a fact which makes it a readily available tool for evaluating patients, planning facial surgery, or delineating basic features of craniofacial syndromes. Anthropometry lacks the detail of more powerful technologies, but it is better suited for populational studies because of the availability of comparative, normal databases. The standard z-scores produced by such comparisons lend themselves to multivariate analysis. This type of comparative analysis is not yet possible for computerized tomography, three-dimensional imaging, or photogrammetry. To illustrate the utility of this technique an example is cited from an ongoing study of hypohidrotic ectodermal dysplasia (HED) in which anthropometry reveals details of facial morphology overlooked in previous studies. These include the presence of reduced facial height and a striking reduction in the size of the facial features in spite of the fact that facial widths are comparatively normal. Gene carriers show a similar though nonidentical pattern of defects. Like all morphometric approaches, anthropometry has its limitations. Well-designed protocols minimize these limitations by incorporating multiple facial dimensions in the analysis and by emphasizing careful collection of data with standard instruments and methodology.

Cephalometry↗