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At least 73 records · Page 4Linked to original sources
PubMed1985

Stereometry in very close-range stereophotogrammetry with non-metric cameras for human movement analysis.

In this paper a stereophotogrammetric algorithm based on a black-box approach to the modelling of object to image spaces relationship is proposed. The algorithm is well suited for 'very close-range photogrammetry', with respect to experiments in which the measurement field is 0.5 X 0.5 X 0.5 m or smaller, as in the analysis of a few or small body segments movements. The attainable accuracy is high, better than 0.1% of the observation distance. Non-professional and even different cameras can be used. Consequently an inexpensive experimental set-up can be realized. A very simple, cheap and easily usable calibration object is needed. Computation time for the reconstruction of object-space co-ordinates of point body landmarks is one order of magnitude lower than in the case of the Direct Linear Transformation (DLT) (Abdel Aziz and Karara, Proceedings of the ASP/U1 Symposium on Close-Range Photogrammetry, pp. 1-18. American Society of Photogrammetry, 1971; Marzan and Karara, Proceedings of the Symposium on close-range Photogrammetric Systems, pp. 420-467. American Society of Photogrammetry, 1975). Computation time for calibration is two-fold in respect of the DLT. An example of application to the recording of the movements of the index finger with respect to the metacarpophalangeal joint is given.

Biomechanical Phenomena↗
PubMed1989

Comparison of three techniques for measuring wear of dental restorations.

Measurements of impression profiles, profilometer registrations, and scanning electron microscopy (SEM) photogrammetry of metal dies simulating worn restorations were compared as possible techniques for measuring and recording the wear rate of tooth restorations. The results showed that measurements of impression profiles and SEM photogrammetry gave the most accurate results adjacent to regions simulating steep cavity margins, whereas the profilometric technique gave erroneous results in these regions. These errors were related to interference between the conical stylus tip and the steep edges. Moreover, photogrammetry was time-consuming and complex and did not result in better overall precision than with the other evaluation techniques. These drawbacks with SEM photogrammetry were related to complex use of software and low precision of crucial hardware components such as SEM tilt stage and digitizer.

Dental Materials↗
PubMed1990

[Use of x-ray computed tomographic data for the concept of a custom-made hip prosthesis. Exploratory approach].

A custom-made hip prosthesis has to allow to improve the arthroplasty's longevity. In a Computer Aid program Conception (CAD) of such an implant, it becomes necessary to control the accuracy of the 3-D data given by CT Scans. The method employed is based on the comparison between 3-D data given by CT Scans and by photogrammetry. The study was made with a human pelvis including femoral head, without soft tissues. The CT Scans data have been given by automatic extraction of osseous outlines on two hundreds sections (1.5 mm thickness). The photogrammetry data have required five stereocouples for the whole pelvis and four stereocouples for the hip joint (femoral head and cotyle). There nine stereocouples have provided 37,213 points of reference. The comparison between the two sorts of informations shows that the error made in CT Scans acquisition was varying between 0.65 and 1.60 mm. This error is smaller when the outlines are simple, like the femoral diaphyse. The error decreases if we reduce the field size of CT Scan acquisition. These results confirm literature data. But this study has allowed to demonstrate validity of 3-D CT reconstruction. Scanography looks like the best present way of data acquisition. The dimensional précision is sufficient to define the endo-osseous outline, but it must be preserved at the moment of the extraction of this outline. Therefore this extractive can't be manual and must be made directly with processing data given by scanography.

Hip Prosthesis↗
PubMed1979

[Comparative clinical and photogrammetric studies on the marginal periodontium after the use of dentifrices].

A suggestion was made for testing the therapeutic effect of certain substances on gingival inflammation. Gingivitis was induced in 60 subjects by discontinuing of all forms of oral hygiene. Three tooth pastes, one of which was a placebo, were used for the study. Regression of the inflammation was determined with the periodontal indexes and photogrammetry. Photogrammetry appears to be well suited for objective evaluation of the therapeutic value of certain substances.

Dental Plaque↗
PubMed1986

[Optical methods in the study of superficial displacements of the lumbar vertebrae under a vertical load. Initial results and methodological aspects].

In order to assess superficial displacements under load in human lumbar vertebrae, the authors used three different optical methods: photogrammetry under non coherent light; double-exposure holographic interferometry; speckle granularity under laser exposure. Without any structural interposition, the displacements are measured within 10 mu for linear variations and 0.1 degrees for angular variations. Photogrammetry seems to be more adequate for the study of large range of displacements while holographic and speckle techniques are useful to assess, in the displacements, the part of the disc and the osseous structure deformation respectively.

Biomechanical Phenomena↗
PubMed1989

A three-dimensional musculoskeletal model for gait analysis. Anatomical variability estimates.

Three-dimensional coordinates defining the origin and insertion of 40 muscle units, and bony landmarks for osteometric scaling were identified on dry bone specimens. Interspecimen coordinate differences along the anterior-posterior axis of the pelvis and the long bone axes of the pelvis, femur and leg were reduced by scaling but landmark differences along the other axes were not. The coordinates were mapped to living subjects using close-range photogrammetry to locate superficial reference markers. The error of predicting the positions of internal coordinates was assessed by comparing joint centre locations calculated from local axes defining the orientation of segments superior and inferior to a joint. A difference was attributed to: anatomical variability not accounted for by scaling; errors in identifying and placing reference landmarks; the accuracy of locating markers using photogrammetry and error introduced by marker oscillation during movement. Anatomical differences between specimens are one source of error in defining a musculoskeletal model but larger errors are introduced when such models are mapped to living subjects.

Anthropometry↗
PubMed1980

Stereochronoscopy of the optic disc with stereoscopic cameras.

Goldmann's chronoscopy, a form of time-based photogrammetry of the optic disc, can be accomplished by repeated simultaneous stereophotography. The variations in centration and image orientation are nulled by azimuthal rotation and fusion of two pairs of stereophotographs taken at separate times.

Humans↗
PubMed1989

Malar augmentation. Patient classification and placement.

Aesthetic malar augmentation is described to improve the appearance of patients with flattening of the malar eminence, to create a more youthful appearance of the face, to make the face more oval in appearance, and to de-emphasize prominent nasal or mental profiles. Detailed preoperative analysis of surgical candidates has not been reported. Twenty models studied by photogrammetry of frontal, lateral, and oblique views were analyzed to synthesize ideal measurements of an aesthetic face with particular attention to points describing the malar mound. Photographs of patients operated on were analyzed using computer graphics to compare the synthesized ideal and surgical results. Ideal candidates are defined as those patients with ptotic malar mounds with adequate soft tissue to create a balanced and harmonious result. Examples of candidates and potential pitfalls are presented.

Adult↗
PubMed1987

Surface strain on human intervertebral discs.

The biomechanical functions of the internal components of the intervertebral disc are not well understood. The surface deformation of 17 human cadaveric lumbar intervertebral discs was studied by photogrammetry by adhering small optical targets to the disc surface and thereby recording the length, bulge, and vertical height of lines on the disc surface representing annular fibers. Discs were studied in pure compression, flexion and extension, axial rotation, and shear. Two definitions of a fiber were investigated: first with the end-points of the fiber on the vertebra ("bone-to-bone" definition), second, where the end points of the fiber were just before the disc vertebra junction (the "disc-only" definition). Measurements were compared with a "constant-volume" physical model and with a mathematical model of the intervertebral disc. Fiber strains were 6% or less under physiological conditions. Comparison of results from the two definitions of fiber length showed greater strains for the disc-only definition in compressive loading. Fiber strains were less than in the constant-volume model of comparable dimensions in compressive loading by a factor of about two, thus suggesting fluid loss or end-plate deformations in the physiologic conditions. The mathematical model indicated that the surface strain for intervertebral discs is very sensitive to the disc-height: diameter ratio and to fluid loss from the disc but is less sensitive to the helix angle of the fibers.

Adult↗
PubMed1984

Mathematical kinematics in engineering of endoprostheses. Evaluation of the results of gait analysis.

Certain optical methods (photogrammetry) achieve great precision in analysis of body motion. However, this study clearly shows that the tracing of body surface movement is unsuitable for analysis of actual joint motion, at least in the knee joint, because of the soft tissue shifting which occurs. It is also shown that comparatively simple mathematical-kinematic techniques can be used to check the degree of error of methods of measurement in orthopedics. It is to be assumed that no currently available knee joint prostheses function in a kinematically perfect manner. If the movement of knee joint prostheses is to be optimized and implantation errors affecting kinematics avoided, it seems indispensable, at the current level of technology, to employ X-ray stereophotogrammetry to describe natural knee joint motion.

Biomechanical Phenomena↗
PubMed1982

High density facial measurement: a new automated approach.

A brief summary of research undertaken into facial geometric measurement is furnished, emphasizing the potential of photogrammetric methods. The techniques described solves the long-standing problem of stabilization of the human head for repetitive longitudinal investigations. The basic geometric principles of terrestrial photogrammetry and digital imaging techniques are outlined, as the groundwork for a description of a fully automated method of obtaining a high density geometric delineation of sensitive surfaces by digital methods. The technique is appropriate for any medical purpose dealing with measurement and analysis of soft tissue surfaces, obviating, as it does, the need for head stabilization with its concomitant problems, and also in its provision of a databank capability.

Anthropometry↗
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↗