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At least 91 records · Page 5Linked to original sources
PubMed1987

Photogrammetric technique applied to anthropometric study of hands.

Being concerned with physical anthropometric dimensions to explore avenues of research on hands and their working strategies, a research study was made to develop a suitable method by using available photogrammetric resources. The paper discusses the optimums of details found by this study, viz., the use of a Wild C-40 stereometric camera (for obtaining stereoscopic photographs) and the use of a Wild A7 stereorestitution instrument equipped with digital data acquisition accessories (for obtaining all dimensional information). Three-dimensional data at 21 specific points and for nine specific distances were obtained on each hand of ten persons. Test observations indicate, inter alia, a dimensional accuracy of the order of +/- 0.3 mm obtainable through the working system. Cartographic presentations made in support of the digital data are found to be of help. This also permits to obtain additional data as may be necessary at times. Photogrammetry has the advantage of reducing and maintaining to a minimum all sorts of manipulations necessary in such studies.

Anthropometry↗
PubMed1991

Measurement of finger joint angles and maximum finger forces during cylinder grip activity.

Finger joint angles and finger forces during maximal cylindrical grasping were measured using multi-camera photogrammetry and pressure-sensitive sheets, respectively. The experimental data were collected from four healthy subjects gripping cylinders of five different sizes. For joint angles, an image analysis system was used to digitize slides showing markers. During the calibration of the camera system, both the nonlinear least square and the direct linear transform methods were applied and compared, the former providing the fewer errors; it was used to determine joint angles. Data were collected from the pressure-sensitive grip films by using the same image analysis system as used in the collection of the joint angle data. The method of using pressure-sensitive sheets provided an estimation of the weighted centre of the phalangeal forces. Results indicate that finger flexion angles at the metacarpophalangeal and proximal interphalangeal joints gradually increase as cylinder diameter decreases, but that at the distal interphalangeal joint the angle remains constant throughout all cylinder sizes. It was also found that most of the radio-ulnar deviation and the axial rotation angles at the finger joints deviate from zero, but the deviations are small. For the force measurement, it was found that total finger force increases as cylinder size decreases, and the phalangeal force centres are not located at the mid-points of the phalanges. The data obtained in this experiment would be useful for muscle force predictions and for the design of handles.

Biomechanical Phenomena↗
PubMed1994

Photogrammetric accuracy measurements of head holder systems used for fractionated radiotherapy.

PURPOSE: We describe how stereo photogrammetry can be used to determine immobilization and repositioning accuracies of head holder systems used for fractionated radiotherapy of intracranial lesions. METHODS AND MATERIALS: The apparatus consists of two video cameras controlled by a personal computer and a bite block based landmark system. Position and spatial orientation of the landmarks are monitored by the cameras and processed for the real-time calculation of a target point's actual position relative to its initializing position. The target's position is assumed to be invariant with respect to the landmark system. We performed two series of 30 correlated head motion measurements on two test persons. One of the series was done with a thermoplastic device, the other one with a cast device developed for stereotactic treatment at the German Cancer Research Center. Immobilization and repositioning accuracies were determined with respect to a target point situated near the base of the skull. The repositioning accuracies were described in terms of the distributions of the mean displacements of the single motion measurements. RESULTS: Movements of the target in the order of 0.05 mm caused by breathing could be detected with a maximum resolution in time of 12 ms. The data derived from the investigation of the two test persons indicated similar immobilization accuracies for the two devices, but the repositioning errors were larger for the thermoplastic device than for the cast device. Apart from this, we found that for the thermoplastic mask the lateral repositioning error depended on the order in which the mask was closed. CONCLUSION: The photogrammetric apparatus is a versatile tool for accuracy measurements of head holder devices used for fractionated radiotherapy.

Head and Neck Neoplasms↗
PubMed1995

The incorporation of partial shielding of the spinal cord in a tissue deficit compensator in radiotherapy of the thorax.

A method to determine the shape of a patient by placing radiopaque wires and chains on the skin and taking two isocentric X-ray films is described. The wire locations are reconstructed by X-ray stereo photogrammetry, and a beam's eye view of the wire frame structure can be obtained with reference to the original setup of the "stereo-pair" films. An algorithm for paving between the wires with triangular plates is described which allows the calculation of the tissue deficit distance and compensator thickness. The depth and distance to points on the spinal cord are calculated, and the dose rate is calculated using a standard irregular field computation program. The limit for spinal cord tolerance is specified in terms of the maximum daily dose based on an equivalent dose formula. The additional thickness of compensator, required for the posterior field compensator to satisfy the tolerance limit, is calculated. The technique readily accommodates the kyphotic and scoliotic spine and has been in routine clinical use for seven years.

Algorithms↗
PubMed1991

Increased preferential optic disc asymmetry in ocular hypertensive patients compared with control subjects.

The authors determined asymmetrical differences in optic disc cupping and pallor between the right and left eyes of 57 control subjects and 75 patients with ocular hypertension. Photogrammetry was used to measure the optic disc cup, and computerized image analysis was used to measure the optic disc pallor for the total disc and its quadrants. Generally, for control and ocular hypertensive eyes, the median values of cupping and pallor were significantly larger in the left eye than in the right, except for depth in the inferior quadrant (right eye minus left eye = 9.3%, P = 0.000) and pallor in the nasal quadrant (right eye minus left eye = 21.3%, P = 0.01), which were preferentially larger in the right eye than in the left in ocular hypertensive eyes. Ocular hypertensive eyes also showed a greater difference between the right and left eyes compared with control eyes for inferior depth (P = 0.06) and nasal pallor (P = 0.02). Detection of optic disc differences as a sign of ocular hypertension between the right eye and the left should evaluate the inferior and nasal quadrants of the disc.

Aged↗
PubMedDate not supplied

[Late results of the surgical correction of funnel chest. Evaluation with subjective and objective criteria including moiré topography].

The long term results of 32 patients with funnel chest deformity that were operatively treated by means of Rehbein's metal implants have been reviewed. The investigated criteria were electrocardiography, pulmonary function, radiographical measurements, and photogrammetry of the frontal thoracic plane (Moiré-Topography). There was no significant change of the electrocardiography and pulmonary function due to the operative treatment. Roentgenometric and surface measurement data showed in 40% of the cases investigated minor up to complete relapses. According to the results the indications for operative treatment and the importance of the patient's age at this time are discussed.

Adolescent↗
PubMed1994

Three-dimensional motion of the upper cervical spine in rheumatoid arthritis.

Rheumatoid arthritis frequently contributes to instability of the upper cervical spine. Rotational instability of the upper cervical spine was evaluated in rheumatoid arthritis patients using biplanar x-ray photogrammetry. Three-dimensional cervical motion and the instantaneous axis of rotation of the atlas relative to the axis were evaluated in normal and rheumatoid arthritis patients during axial rotation in the horizontal plane. Anterior atlantoaxial subluxation did not increase during axial head rotation in either the atlantoaxial subluxation or the vertical subluxation groups, while the instantaneous axes of rotation were distributed posteriorly in the dens in the RA-normal group, but were widely scattered in the atlantoaxial subluxation group.

Arthritis, Rheumatoid↗
PubMed1978

Calculation of surface area and volume of human erythrocytes from scanning electron micrographs.

This article demonstrates that surface and volume measurements of individual human erythrocytes with varying shapes can be obtained from scanning electron micrographic stereopairs using an approach based on established principles of photogrammetry. Instead of calculating the coordinates of several hundred points plotted for each cell, a procedure that proves tedious and time-consuming, we show that a reasonable approximation of cell surface and volume can be achieved from simple geometrical models constructed with a small number of carefully measured points and angles, using a stereocomparator. The values obtained for two normal erythrocytes and for two distorted red cells from a patient with congenital pyruvate kinase deficiency haemolytic anaemia are consistent with available information on the geometry of these cells. Because scanning electron microscopy requires extensive manipulation of the cells, the values obtained cannot be applied to fresh living material, but appear fairly accurate for the purpose of comparison between cells prepared in the same manner.

Anemia, Hemolytic, Congenital↗
PubMed1981

Photogrammetric registration of dental plaque accumulation in vivo.

Using the labial surface of upper anterior laterals for determination, the accumulation of plaque was assessed by means of a stereo-photogrammetric method. The stereoimages were subjected to photogrammetric evaluation, the part of the surface area covered by plaque being given in per cent of the total surface area of the tooth. Plaque extension and plaque topography was studied in young adults with healthy periodontia during a 20 day period of no oral hygiene. At the end of the experimental period, on an average 75 per cent of the surface area was covered by plaque, corresponding to an extension rate of 3.75 per cent per day. The correlation between plaque values obtained by photogrammetry and various estimates obtained from clinical scoring ranged between r = 0.66 and r = 0.78. It is concluded that the method introduced is a sensitive means of determining small amounts of plaque and should prove useful for in vivo investigation of plaque growth and plaque suppression, where measurements of high quality is of importance.

Adult↗
PubMed1975

[Objective radiological stereophotogrammetry in dentistry].

By means of objective radiological stereo-photogrammetry of two extraoral stereoscopic radiograms, the location of dislocated impacted teeth was determined preoperatively in a model. During operation it was possible to find the teeth at the computed position.

Female↗
PubMed1975

Calibration and measurement in 3-dimensional monitoring of human motion by optoelectronic means. I. Preliminaries and theoretical aspects.

By combinding the obervations from a number of independent direction sensors, the spatial positions of one or more targets may be reconstructed. The theory of calibration and measurement in a computerized, interactive environment is discussed in the terminology of analytical photogrammetry, for applications in the field of biomechanics. The discussion is focussed upon optoelectronic system for movement monitoring in real-time rather than upon photography as is the conventional photogrammetric implementation.

Biomechanical Phenomena↗
PubMed1989

Shadow photogrammetric apparatus for the quantitative evaluation of corneal buttons.

We have developed a technique for the accurate, quantitative, geometric evaluation of trephined and punched corneal buttons. A magnified shadow of the frontal and edge views of a corneal button mounted on the rotary stage of a modified optical comparator is projected onto the screen of the comparator and photographed. This process takes approximately three minutes. The diameters and edge profile at any meridian photographed can subsequently be analyzed from the film. The precision in measuring the diameters of well cut corneal buttons is +/- 23 microns, and in measuring the angle of the edge profile is +/- 1 degree. Statistical analysis of inter observer variability indicated excellent reproducibility of measurements. Shadow photogrammetry offers a standardized, accurate, and reproducible method for analysis of corneal trephination.

Calibration↗
PubMed1988

Spine and back-shape changes in scoliosis.

Thirty-five untreated patients with scoliosis were studied by Cobb radiography and back-surface photogrammetry on each of at least two clinic visits. Also, the maximum vertebral axial rotation was measured. Each pair of patient visits was classified as showing either a progression, improvement, or no change in the scoliosis using a threshold of 5 degrees change in the Cobb angle. The computer Cobb measurement was the most precise measurement, and the back-surface measurements were the least precise. The Cobb measurement of scoliosis is the most precise for detecting small changes, but can be improved by a computerized analysis of digitized radiographs.

Adolescent↗
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↗
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↗