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Results for “Photogrammetry”

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PubMed1986

Changes in optic disc in ocular hypertension and glaucoma.

Most ophthalmologists use subjective methods to evaluate the optic disc for abnormalities and changes that occur in ocular hypertension and glaucoma. We have developed new techniques that allow more accurate evaluation of the blood supply to the optic disc and of changes in disc cupping and pallor. To evaluate the blood supply we use the technique of fluorescein angiography of the optic disc. With this technique, we have found that fluorescein defects commonly appear in open-angle glaucoma and ocular hypertension and are more frequent and larger in glaucomatous and ocular hypertensive discs than in normal optic discs. Fluorescein angiography demonstrates distinct changes in the blood supply to the optic disc in the glaucomatous or ocular hypertensive eye. Cupping of the optic disc is measured by photogrammetry from stereophotographs, which provide three-dimensional measurements not only of the volume of the cup, but of the depth, the slopes of the walls of the optic cup, and the area of the surface opening. This technique also allows us to determine a volume profile of the cup: that is, its cross-sectional area from top to bottom. The volume profile characterizes the shape of the optic cup and shows distinct differences in shape between normal, ocular hypertensive and glaucomatous cups. Pallor is measured by computerized image analysis. This technique allows us to determine the percent area of pallor of the optic disc. These three techniques permit us not only to evaluate abnormalities, but to measure changes over time in the optic disc in ocular hypertension and glaucoma, thereby increasing our diagnostic capability and improving patient management.

Computers↗

PubMed1985

Reproducibility of photogrammetric optic disc cup measurements.

To detect early glaucoma-associated changes in the optic disc cup, the authors analyzed reproducibility of optic disc cup measurements by photogrammetry of three age-matched groups: 10 normal, 10 ocular hypertensive, and 10 glaucomatous subjects. For each eye, three simultaneous stereophotographs were taken on the same day and one measurement was made for each stereophotograph. In order to reduce the effects of refractive error of the eye and photographic magnification, the authors computed cup parameters as relative measurements, ie, a ratio to the optic disc area. The median coefficients of variation for glaucomatous eyes were 4.5% for cup volume/disc area, 6.1% for cup depth/disc area, and 4.7% for cup area/disc area. Coefficients of variation of normal and ocular hypertensive subjects were slightly larger than those of glaucomatous subjects. Coefficients of variation generally were larger for quadrants than for total disc area. These findings suggest that the photogrammetric technique is highly reproducible and sensitive and could be a valuable quantitative technique for the clinical study of glaucoma.

Glaucoma, Open-Angle↗

PubMed1993

[Anterior chamber dimensions in normal subjects on Kume Island, Okinawa].

The anterior chamber dimension and axial length were studied by photogrammetry and ultrasonography in 365 normal subjects over 21 years of age on Kume island, Okinawa. There was no difference between right and left eyes in the anterior chamber dimensions, corneal curvature, or axial length. Male subjects had a larger anterior chamber and longer axial length than female subjects. The volume, depth, and diameter of the anterior chamber diminished with age and degree of hyperopia. The axial length was related to the anterior chamber dimensions, corneal curvature, and degree of ametropia. The anterior chamber dimensions and axial length in subjects over 60 years of age on Kume island were significantly smaller than in normal subjects over 60 years in Tokyo.

Adult↗

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↗

PubMed1996

[Pathophysiology of the abdominal wall].

The use of biomaterials for closure of incisional hernias requires meshes adjusted to the physiological forces. The intraabdominal pressure is mainly influenced by the activity of the transverse muscles. The abdominal fascia of corpses withstands forces of 60-80 N/cm in horizontal and 20-30 N/cm in vertical direction; tearing of sutures occurs below 30 N/cm in horizontal direction. Assuming the abdominal cavity to be a thin hollow sphere, the rupture forces are approximately 4-16 N/cm for a diameter of 8-3 cm. The meshes currently in use are much stronger than this, rupturing at 40-100 N/cm. The curvature of the abdominal surface can be measured by 3D-photogrammetry and is highly significantly reduced following mesh implantation (t-test, 2-sided, P < 0.01). Reduction of the mesh material can decrease the rate of local wound complications and the stiffness of the abdominal wall.

Abdominal Muscles↗

PubMed1997

Objective techniques for craniofacial assessment: what are the choices?

The approach to an individual with unusual facial appearance has traditionally involved a subjective assessment coupled with a few craniofacial measurements. Our ability to describe facial morphology has improved in recent years through the development of new techniques such as computerized tomography, magnetic resonance imaging, ultrasound studies, and stereoscopic imaging. However, the relatively simpler techniques of anthropometry, cephalometry, and photogrammetry, developed prior to the advent of microchips and imaging software, continue to provide unique advantages not afforded by these technically more sophisticated methods. These objective methods should enhance pattern recognition, particularly in rare syndromes, and allow for earlier diagnosis.

Anthropometry↗

PubMed1998

Facial volume changes during normal human growth and development.

BACKGROUND: To describe normal soft tissue growth and development of the human face through volume changes and to assess the presence of sexual dimorphism. METHODS: Facial landmark identifications (2,023) were performed on 1,347 healthy Caucasian children and adolescents, ages 6-18 yr, and young adults, ages 19-32 yr. Three-dimensional coordinates of 22 facial landmarks were collected by automated infrared photogrammetry. Facial volumes and selected linear distances and ratios were calculated and averaged for age and sex. RESULTS: Whereas in females in the 14-15 age group, the face had almost completed its growth relative to the adult group, in males a large increase was still to occur, in general agreement with previous reports on craniofacial growth, which suggested a strong tendency in males for growth to continue for several years beyond that seen in females. The male vs. female comparison reflected the different growth patterns. On average, within each age group volumes were significantly larger in males than in females, with some exceptions in the 11-12 age group, where female growth velocity showed a spurt. Sexual dimorphism in facial volume did not appear in different parts of the face to the same extent: a large part of male facial volume preponderance occurred in the lower third of the face. CONCLUSIONS: From 6 yr of age to adulthood, facial soft tissues increased their volumes by >40%, with different growth patterns in boys and girls.

Adolescent↗

PubMed2001

Soft tissue facial resemblance in families and syndrome-affected individuals.

We investigated soft tissue facial resemblance among relatives with or without syndromes and among related and unrelated individuals diagnosed with the same syndrome. Using correlation coefficients, we compared facial landmark (i.e., three-dimensional coordinate) positions and measurements gained by photogrammetry in various combinations of normal and syndrome-affected individuals. There were fewer significant correlations for the three-dimensional coordinates and measurements between the normal parent-normal child pairs than for the normal sib pairs. There was no discernible pattern for the single measurements in the parent-child pairs, whereas all of the midline vertical measurements were significantly positively correlated in the normal sib pairs. Significant correlations were always positive in all sib comparisons, but ranged from negative to positive in all parent-child correlations. The shared environment of sibs was a possible explanation for their greater resemblance in comparison with parent-child pairs. We also had measurements from 11 subjects (related and unrelated) diagnosed with one of four syndromes, and we used these to compare individuals with the same syndrome by calculating correlation coefficients based on all available pairs of measurements. The highest significant positive correlations were found for related individuals with the same syndrome (0.72 to 0.83). Unrelated individuals with the same syndrome also had significant positive correlations, but they were lower (0.35 to 0.65). We therefore inferred that the genetic similarities between unrelated individuals with syndromes played a role in the resemblance between them, and that common genes and environment in related individuals further contributed to the high correlations found for them.

Adult↗

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↗

PubMed2005

Acoustic mirror effect increases prey detection distance in trawling bats.

Many different and phylogenetically distant species of bats forage for insects above water bodies and take insects from and close to the surface; the so-called 'trawling behaviour'. Detection of surface-based prey by echolocation is facilitated by acoustically smooth backgrounds such as water surfaces that reflect sound impinging at an acute angle away from the bat and thereby render a prey object acoustically conspicuous. Previous measurements had shown that the echo amplitude of a target on a smooth surface is higher than that of the same target in mid-air, due to an acoustic mirror effect. In behavioural experiments with three pond bats (Myotis dasycneme), we tested the hypothesis that the maximum distances at which bats can detect prey are larger for prey on smooth surfaces than for the same prey in an airborne situation. We determined the moment of prey detection from a change in echolocation behaviour and measured the detection distance in 3D space from IR-video recordings using stereo-photogrammetry. The bats showed the predicted increase in detection distance for prey on smooth surfaces. The acoustic mirror effect therefore increases search efficiency and contributes to the acoustic advantages encountered by echolocating bats when foraging at low heights above smooth water surfaces. These acoustic advantages may have favoured the repeated evolution of trawling behaviour.

Animals↗

PubMed2001

Images of the invisible-prospection methods for the documentation of threatened archaeological sites.

To understand the development of prehistoric cultural and economic activities, archaeologists try to obtain as much relevant information as possible. For this purpose, large numbers of similar sites must be identified, usually by non-destructive prospection methods such as aerial photography and geophysical prospection. Aerial archaeology is most effective in locating sites and the use of digital photogrammetry provides maps with high accuracy. For geophysical prospection mainly geomagnetic and geoelectrical methods or the ground-penetrating radar method are used. Near-surface measurements of the respective contrasts within physical properties of the archaeological structures and the surrounding material allows detailed mapping of the inner structures of the sites investigated. Applying specially developed wheeled instrumentation, high-resolution magnetic surveys can be carried out in a standard raster of 0.125 x 0.5 m covering up to 5 ha per day. Measurements of ground resistivity or radar surveys in a raster of 0.5 or 0.5 x 0.05 m, respectively, are used to gain information on archaeological structures and on the main stratigraphic sequence of sites covering up to 0.5 ha per day. Data on intensities of the Earth's magnetic field, apparent resistivities of the ground or amplitudinal information of radar reflections are processed using a digital image processing technique to visualize the otherwise invisible archaeological structures or monuments buried in the ground. Archaeological interpretation, in the sense of detecting, mapping and describing the archaeological structures, is done using GIS technology by combining all relevant prospection data. As most of the Middle European archaeological heritage is under a massive threat of destruction, dramatically accelerated by intensive agriculture or industrial transformation of the landscape, the prospection techniques presented here represent an approach towards an efficient documentation of the disappearing remains of our ancestors.

Archaeology↗

PubMed2002

Functional and morphologic properties of a modified mesh for inguinal hernia repair.

Inguinal hernia repair is one of the most frequently performed operations. Next to conventional techniques, open and laparoscopic tension-free methods using mesh implants to reinforce the abdominal wall are increasingly carried out, even becoming the standard procedure in many countries. Because of the benefits of material-reduced meshes for incisional hernia repair, a new mesh modification for tension-free inguinal hernia repair has been developed. In the present study this new low-weight mesh (Vypro II) made of polypropylene and polyglactin multifilaments was compared to a common heavy-weight polypropylene mesh (Prolene) regarding their functional consequences and the morphologic tissue response. After implantation in rats as an inlay, abdominal wall mobility was recorded by three-dimensional photogrammetry and the tensile strength of the suture zone and the mesh itself was measured at 3, 21, and 90 days. Explanted tissue samples have been investigated for their histologic reaction in regard to the inflammatory infiltrate, vascularization, and connective and fat tissue ingrowth. Numbers of granulocytes, macrophages, fibroblasts, lymphocytes, and foreign giant body cells have been evaluated to reflect the quality of the tissue response. The cellular response was assessed by measuring DNA strand breaks and apoptosis (TUNEL), proliferation (Ki67), and cell stress (HSP70). The results indicated that restriction of abdominal wall mobility was significantly reduced with Vypro II compared to that seen with heavy-weight mesh modification, and the inflammatory reaction and connective tissue formation were markedly diminished. Apoptosis and cell proliferation showed considerably lowered levels, and expression of cytoprotective HSP70 was significantly increased. The present study thus confirms the benefits of material-reduced mesh modifications. The new low-weight mesh (Vypro II) could be advantageous in inguinal hernia repair.

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↗

PubMed2001

Spatial reconstruction of the human motion based on images of a single camera.

The inverse dynamic analysis procedures used in the study of the human gait require that the kinematics of the supporting biomechanical model is known beforehand. The first step to obtain the kinematic data is the reconstruction of human spatial motion, i.e., the evaluation of the anatomic points positions that enables to uniquely define the position of all anatomical segments. In photogrammetry, the projection of each anatomical point is described by two linear equations relating its three spatial coordinates with the two coordinates of the projected point. The need for the image of two cameras arises from the fact that three equations are necessary to find the original spatial position of the anatomical point. It is shown here that the kinematic constraint equations associated with a biomechanical model can be used as the extra set of equations required for the reconstruction process, instead of the equations associated with the second camera. With this methodology, the system of equations arising from the point projections and biomechanical model kinematic constraints are solved simultaneously. Since the system of equations has multiple solutions for each image, a strategy based on the minimization of the cost function associated to the smoothness of the reconstructed motion is devised, leading to an automated computer procedure enabling a unique reconstruction.

Biomechanical Phenomena↗