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At least 307 records · Page 17Linked to original sources
PubMed1981

Growth disturbance after physial injury of distal femur and proximal tibia studied by roentgen stereophotogrammetry.

Longitudinal growth determined by roentgen stereophotogrammetry was registered in three patients with physial injuries in distal femur and in two patients with physial injuries in proximal tibia during 18 months. The injuries in distal femur were classified as Type I, Type I kII and Type IV and in proximal tibia as Type I kII and Type IV in the different cases according to Salter and Harris. Markers of tantalum balls were implanted into the metaphysis and bony epiphysis of distal femur and proximal tibia permitting regular determination of longitudinal growth. Significant growth disturbances was registered in four patients. The Salter-Harris classification was difficult to use to predict growth disturbance after physial injuries around the knee. The roentgen stereophotogrammetric method was found useful to determine normal growth rate and after physial injuries to reveal growth disturbance leading to complete or partial growth arrest resulting in leg length discrepancy or angular deformity. This method facilitates preoperative planning if surgery is needed.

Adolescent↗
PubMed1993

Laser scanning tomography and stereophotogrammetry in three-dimensional optic disc analysis.

Laser scanning tomography (LST) and computed stereophotogrammetry (CSP) are sophisticated diagnostic tools for the three-dimensional analysis of optic nerve head topography. The two methods are based on different physical principles. To compare the information about the shape of the cup of an optic nerve head obtained by LST and CSP, we evaluated the volume profile (VP; i.e., the cross-sectional area of the cup from top to bottom) in 36 discs of 36 patients (20 control group discs C, 16 glaucoma discs G). The Spearman correlation coefficient between the photogrammetric and the laser scanning VP-slope measurements was rs = 0.931; P < 0.001 (rs = 0.935 G, P < 0.001; rs = 0.910 C, P < 0.001). The results suggest that confocal laser scanning provides readings of the shape of the optic disc cup that are similar to the measurements of computed stereophotogrammetry.

Adolescent↗
PubMed1994

Kinematics of successful knee prostheses during weight-bearing: three-dimensional movements and positions of screw axes in the Tricon-M and Miller-Galante designs.

Using roentgen stereophotogrammetric analysis we recorded the three-dimensional movements in six knees with implanted Tricon-M prostheses and ten knees with Miller-Galante prostheses as the patients ascended a platform. Fourteen patients with normal knees were used as controls. The two prosthetic designs displayed decreased internal tibial rotation and the Tricon-M increased valgus rotation. A central point on the tibial articular surface had a more lateral position in the Tricon-M design and a more distal one in the Miller-Galante design compared to normal knees. Increased posterior displacement with increasing flexion was observed in both designs. When the normal knees were extended at full weight-bearing the helical axes mainly shifted inclination in the frontal plane. In the prosthetic knees there was a tendency to anterior-posterior displacement of the axes as extension proceeded, especially in the Miller-Galante design. Translations along the helical axes were larger than normal in the Miller-Galante and smaller in the Tricon-M knees, reflecting differences in constraint of the two designs.

Aged↗
PubMed1977

Corneal topography.

This paper explores the many aspects of the nature and measurement of the corneal surface. Its structure and the factors that influence it are described. The traditional techniques of keratometry are summarized and there is an emphasis on new experimental methods of determining corneal topography including moiré, holographic interferometric and profile techniques. The advantages and disadvantages of these procedures are considered.

Adult↗
PubMed1986

Some aspects of knee joint kinematics in rheumatoid arthritis as studied with roentgen stereophotogrammetry.

Kinematic studies of the rheumatoid knee joint with the aid of roentgen stereophotogrammetry were performed in 4 patients (6 knees). Three kinds of experiments were carried out. The screw axis of rotation between various flexion angles was determined. The displacement of the screw axis indicated pathological function in all cases. Using different treatment techniques the effect of traction was studied. A separation between the femur and the tibia of 1.3-3.8 mm was found in 3 knees which were slightly flexed during the traction. The compression effect of isometric knee extension was determined in 4 knees. Compression of 0.5 mm at a medial point and of 0.3 mm at a lateral point of the femoral condyle were found in one knee. The present study indicates that roentgen stereophotogrammetric analysis may give additional information on the development of internal derangement of the rheumatoid knee joint.

Arthritis, Rheumatoid↗
PubMed1984

Quantitative studies in stereochronoscopy (Sc): application to the disc in glaucoma. II. Statistical evaluation.

The statistical method of control charts applied to quantitative stereochronoscopy of the disc in glaucoma enables differentiation of cases of to and fro displacements of disc elements ("papillary unrest") from continuous or discontinuous progression. In all cases of discontinuities we are obliged to search for their cause. The control chart method helps to determine the approximate time of incidence of these events. Stereochronoscopy should be well adapted to supervise treated glaucoma cases.

Circadian Rhythm↗
PubMed1982

Biometric study of the disc cup in open-angle glaucoma.

Stereoscopic and photogrammetric study of the disc cup in open-angle glaucoma reveals several morphological changes. The ovalisation of the cup, upwards, downwards or on the temporal side, appears early. It can be detected at the onset of the disease, even in the absence of visual field defects. It results in a localised thinning of the nervous rim, which is a characteristic sign of beginning glaucoma, but the depth of the cup is not increased even when perimetry already reveals important defects. The aim of this paper is to study, on the one hand, the morphological changes of the disc cup and on the other, the functional defects in open-angle glaucoma, and then to compare the results of the investigations.

Adult↗
PubMed2003

Eye feature extraction for diagnosing the facial phenotype associated with fetal alcohol syndrome.

Victims of fetal alcohol syndrome (FAS) exhibit a unique facial phenotype that is emphasised in diagnosis. Among the characteristic facial features, several occurring in the region of the orbits can be evaluated quantitatively using distance measurements. An algorithm is described for automatic extraction and measurement of eye features from stereo photographs. The algorithm was applied to photographs of 46 six-seven-year-old children. The approach relies on peak and valley maps and integral projection functions, to locate the eyes and extract the iris, and genetic algorithms to fit cubic splines to the upper and lower eyelids. Measurements obtained automatically using this algorithm were compared with measurements obtained manually from the photographs. Mean absolute differences between automatic and manual measurements were less than 1 mm for palpebral fissure length (PFL) and interpupillary distance (IPD). Absolute differences were less than 1 mm for 80.4% of PFLs and 100% of IPDs. Inner canthal distance and outer canthal distance did not compare favourably with manual measurements.

Algorithms↗
PubMed2002

Using three-dimensional difference maps to assess changes in scoliotic deformities.

The three-dimensional nature of scoliosis, coupled with changes due to natural history or treatment, is often difficult to quantify and visualise. A difference map was developed to compare the sequential surface topography of subjects over their treatment period. Three-dimensional surface maps representing patients' trunk surfaces were captured with a laser scanner. Patient surface maps from two clinic visits were matched using a manual best-fit technique that accounted for growth and positioning. The surfaces were subtracted, generating a colour-coded three-dimensional difference map displaying the surface changes. The difference maps were compared with known clinical measures, indicating good agreement (78% specific) with the clinical parameters in detecting change. Full agreement or agreement with the clinical parameters occurred in the surgical, brace and no treatment groups: 76%, 80% and 85%, respectively. A difference index (average of the absolute value of differences on a point-by-point basis) was calculated from the difference map, enabling quantification of change. The difference index, with zero being a perfect match, averaged 5 +/- 1 for repeated measures 7 +/- 2 for subjects deemed to have no change, 9 +/- 2 for subjects with slight change, and 14 +/- 2 for subjects with significant change. The difference map showed the extent and location of changes and is a useful tool for assessing surface topography changes.

Adolescent↗
PubMed2000

Integrated pressure-force-kinematics measuring system for the characterisation of plantar foot loading during locomotion.

Plantar pressure, ground reaction force and body-segment kinematics measurements are largely used in gait analysis to characterise normal and abnormal function of the human foot. The combination of all these data together provides a more exhaustive, detailed and accurate view of foot loading during activities than traditional measurement systems alone do. A prototype system is presented that integrates a pressure platform, a force platform and a 3D anatomical tracking system to acquire combined information about foot function and loading. A stereophotogrammetric system and an anatomically based protocol for foot segment kinematics is included in a previously devised piezo-dynamometric system that combines pressure and force measurements. Experimental validation tests are carried out to check for both spatial and time synchronisation. Misalignment of the three systems is found to be within 6.0, 5.0 and 1.5 mm for the stereophotogrammetric system, force platform and pressure platform, respectively. The combination of position and pressure data allows for a more accurate selection of plantar foot subareas on the footprint. Measurements are also taken on five healthy volunteers during level walking to verify the feasibility of the overall experimental protocol. Four main subareas are defined and identified, and the relevant vertical and shear force data are computed. The integrated system is effective when there is a need for loading measurements in specific plantar foot subareas. This is attractive both in clinical assessment and in biomechanics research.

Biomechanical Phenomena↗
PubMed2001

Spot check of the calibrated force platform location.

In a movement analysis laboratory, stereophotogrammetric motion capture systems and force platforms must share one absolute reference frame that allows the computation of joint moments and powers. The correct calibration of the platform location identifies the transformation between force plate and absolute reference systems, which determines the spatial coherence among the equipments' measurements. The aim of this study was to develop and test a spot check for the assessment of platform location calibration. Platform location calibration was assessed by comparing the measured outcome of an experiment performed with a pointed rigid rod bearing a set of markers with the corresponding expected results, computed with a model. A set of indices was then proposed to define a confidence volume in which the true ground reaction force is expected to be. The spot check was applied to a real laboratory setup and the effects of simulated platform mislocations were analysed. It was verified that the hip joint moment may be equally affected by a single marker misplacement of about 20mm during platform location calibration, an occurrence that was clearly identified by the spot check, and by a hip centre location inaccuracy of 30mm.

Biomechanical Phenomena↗
PubMed2000

A spot check for estimating stereophotogrammetric errors.

Good practice rules in the management of a movement analysis laboratory recommend that photogrammetric measurement errors are assessed, prior to every experimental session, using an ad hoc experiment referred to as a spot check. The paper proposes an inexpensive and easy to make spot check. The test uses a rigid rod carrying two markers and a target point taken on the line joining them and coinciding with the rod tip. The latter point is placed in a fixed and measured position in the laboratory frame and the markers are tracked while the rod is kept stationary and while it is manually made to rotate about the target point. Several target points are used within the measurement volume. The instantaneous errors with which the laboratory co-ordinates of the latter points are reconstructed are determined and submitted to statistical analysis. A normalisation procedure is illustrated that aims at making the test results independent from the geometry of the test object. The experimental and analytical methods underlying the proposed spot check were validated experimentally in two movement analysis laboratories using repeated tests. A rod, 1.5 m long, carrying four markers was used. In this way, several test-object geometries were tested. Results confirmed that the photogrammetric error could be divided into a zero-mean random and a systematic component. It was shown that the normalisation procedure was effective for the standard deviation of both error components when the two markers were located at a distance between them 1.5 times larger than the distance of their centroid from the tip of the rod. The systematic component bias could not be normalised, however a conservative value of it could be estimated. The two above-mentioned normalised standard deviations and the bias value can be taken as descriptors of the photogrammetric error of the specific measuring system tested. These parameters may also be used to assess the precision and the accuracy with which the laboratory position of a target point, defined relative to any specified marker cluster, may be reconstructed during movement analysis.

Humans↗
PubMed1986

Validity and reliability of biostereometric measurement of the human female breast.

A measurement technique has been developed for application in the area of noninvasive breast cancer detection. The measurement process involves the use of close-range stereophotogrammetry as a data acquisition device necessary for determination of breast volume and volume distribution. This report details the methodology used to acquire and analyze stereopair photographs necessary to document the validity and reliability of this application. The volume of a test object was determined by both water displacement and stereophotogrammetric analysis to estimate the precision of the proposed methodology. Additionally, the reliability component of the study was documented by analyzing variability of coordinates representing a series of locations marked on the surface of an irregularly shaped object. Both tests confirm that this stereometric analysis is a reliable and valid method of measurement and may be well suited for further development in the field of breast cancer detection.

Biomedical Engineering↗