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At least 91 records · Page 5Linked to original sources
PubMed1985

On the application of photogrammetry to the fitting of jawbone-anchored bridges.

Misfit between a jawbone-anchored bridge and the abutments in the patient's jaw may result in, for example, fixture fracture. To achieve improved alignment, the bridge base could be prepared in a numerically-controlled tooling machine using measured abutment coordinates as primary data. For each abutment, the measured values must comprise the coordinates of a reference surface as well as the spatial orientation of the fixture/abutment longitudinal axis. Stereophotogrammetry was assumed to be the measuring method of choice. To assess its potentials, a lower-jaw model with accurately positioned signals was stereophotographed and the films were measured in a stereocomparator. Model-space coordinates, computed from the image coordinates, were compared to the known signal coordinates. The root-mean-square error in position was determined to 0.03-0.08 mm, the maximum individual error amounting to 0.12 mm, whereas the r. m. s. error in axis direction was found to be 0.5-1.5 degrees with a maximum individual error of 1.8 degrees. These errors are of the same order as can be achieved by careful impression techniques. The method could be useful, but because of its complexity, stereophotogrammetry is not recommended as a standard procedure.

Computers↗
PubMed1979

Photogrammetry of the optic disc in glaucoma and ocular hypertension with simultaneous stereo photography.

Stereophotogrammetric evaluations of the optic cup were performed for normal, ocular hypertensive, and glaucomatous eyes. Average volume, area, and depth measurements were progressively larger from normal to ocular hypertensive to glaucomatous eyes, although the distributions of individual values exhibited considerable overlap among the three groups. Similar results were obtained for volume, area, and depth asymmetry between each pair of eyes. None of these measurements was able to distinguish accurately between normal and glaucomatous optic cups. However, normal eyes showed a high correlation (r = +0.85) between area and depth of the optic cup, whereas this area/depth relationship was reduced in ocular hypertensives (r = +0.63) and completely broke down for glaucomatous eyes (r = +0.04). Approximately 89% of the glaucomatous eyes and 47% of the ocular hypertensive eyes were beyond the range of normal area/depth correlation values. These findings represent an improvement over most previous attempts to quantitatively differentiate between normal and glaucomatous eyes on the basis of optic disc measurements alone, and support the hypothesis that optic disc damage usually precedes visual field loss in glaucoma. With further technical refinements such as computer image processing, stereophotogrammetry of the optic cup may become a valuable differential diagnostic technique for glaucoma.

Glaucoma↗
PubMed1978

Applied X-ray photogrammetry in neurosurgery.

The introduction of X-ray stereophotogrammetry into neurosurgery permits the exact localisation of metal-dense foreign bodies, the spatial representation of cerebral tumours and their blood supply. The determination of the target point in stereotactic operations is carried out after adjustment of the reference points on the X-ray picture directly by the computer, the seat of the probe can be seen in the X-ray picture in its spatial relations. For intracranial aneurysms, the position, the size, and the topographic situation of the neck of the aneurysm can be determined, and thus the placing of the clip during the operation can be pre-planned and made simpler and safer. A description of the photographic technique and the interpretation by means of the new stereocomparator of Messrs. Zeiss is given.

Humans↗
PubMed2004

Image processing for craniofacial landmark identification and measurement: a review of photogrammetry and cephalometry.

Facial surface anthropometry and cephalometry have been used for many years for the diagnosis of malformations, surgical planning and evaluation, and growth studies. These disciplines rely on the identification of craniofacial landmarks. Methods for 3D reconstruction of landmarks have been introduced, as have image processing algorithms for the automation of landmark extraction. This paper reviews facial surface anthropometry and cephalometry with reference to the image processing algorithms that have been applied and their effectiveness.

Algorithms↗
PubMed1981

The measurement of cell volume and surface area by SEM photogrammetry.

The problem of measuring singly the volumes and surface areas of macrophages with their complex and variable morphology was dealt with by the photogrammetric analysis of stereoscopic SEM micrographs. The reproducibility of these measurements was found to be greater than 95%, using the most basic stereophotogrammetric technique.

Animals↗
PubMed2004

Photophysics of laser dye-doped polymer membranes for laser-induced fluorescence photogrammetry.

Laser-induced fluorescence target generation in dye-doped polymer films has recently been introduced as a promising alternative to more traditional photogrammetric targeting techniques for surface profiling of highly transparent or reflective membrane structures. We investigate the photophysics of these dye-doped polymers to help determine their long-term durability and suitability for laser-induced fluorescence photogrammetric targeting. These investigations included experimental analysis of the fluorescence emission pattern, spectral content, temporal lifetime, linearity, and half-life. Results are presented that reveal an emission pattern wider than normal Lambertian diffuse surface scatter, a fluorescence time constant of 6.6 ns, a pump saturation level of approximately 20 microJ/mm2, and a useful lifetime of more than 300,000 measurements. Furthermore, two demonstrations of photogrammetric measurements by laser-induced fluorescence targeting are presented, showing agreement between photogrammetric and physically measured dimensions within the measurement scatter of 100 microm.

Journal Article↗