Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Photogrammetry”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 55 records · Page 3Linked to original sources
PubMed1980

Is photogrammetry of the face reliable?

The reliability of photogrammetry was assessed in 18 healthy young, white Canadians of each sex. Landmarks were indicated on the face before direct measurement and photography. Of 104 surface measurements taken directly from the head, face, and ears of subjects, 62 could be duplicated on the life-size frontal and left lateral photographs taken from the head in standard position. Of these 62 measurements, 26 were reliable (the same as or differing from the direct measurements by no more than 1 mm or 2 degrees). The greatest number of reliable measurements were of the lips and mouth (7 out of 13), but no ear measurements were reliable. Almost half (9) of the reliable measurements were inclinations. More correct vertical measurements were possible from lateral prints than from frontal views, but many lateral facial measurements from profile prints were distorted. Frontal-view prints gave additional reliable measurements.

Adult↗
PubMed1993

Intraoperative raster photogrammetry--the PAR Corneal Topography System.

The PAR Corneal Topography System (CTS) is a computer-driven corneal imaging system that uses close-range raster photogrammetry to measure and produce a topographic map of the corneal surface. The CTS determines distortion in a projected two-dimensional grid. Unlike Placido-disc-based videokeratoscopes, the PAR CTS produces a true topographic map (elevation map) and requires neither a smooth reflective surface nor precise spatial alignment for accurate imaging. Because the system uses two noncoaxial optical paths, it can be integrated into other optical devices. A modified CTS was integrated into an experimental erbium: YAG photoablative laser. The CTS successfully imaged corneas before, after, and during laser photoablation. Its ability to image nonreflective surfaces and to be integrated into other optical systems may make it suitable for intraoperative refractive monitoring.

Animals↗
PubMed1982

Stereo X ray photogrammetry applied for prevention of sigmoid-colon damage caused by radiation from intrauterine sources.

Radiation therapy of cervix carcinoma is applied in this Institute by means of a modified Stockholm method in combination with external beam irradiation. In 1968, parametrial portals were replaced by large planparallel opposed fields extending cranially to LIII/LIV with central shielding in order to avoid overdosage in the area of intracavitary treatment. This resulted in a marked increased incidence of severe sigmoid-colon radiation lesions from 0.25% to 4%; predominantly in Stage I and II patients. Therefore two measures have been introduced: beginning in 1972 measures were taken to prevent the cranial displacement of the uterus during intracavitary treatment in order to avoid shortening the distance between the radioactive sources and the sigmoid-colon; from 1972 stereo X ray photogrammetry (SMR) was applied for dose determinations at points of the sigmoid-colon, which were seen to be located close to the applicator. When SRM data indicated that a high dose at the sigmoid-colon might occur, treatment modifications enabled prevention of radiation damage. Change of position of the applicator was the first to be considered. In the last seven years no surgical intervention had to be performed because of a sigmoid-colon lesion resulting from an unexpected high radiation dose delivered by intrauterine sources. The local recurrence rate was not increased following treatment modifications for prevention of sigmoid-colon radiation damage.

Brachytherapy↗
PubMed2003

Analysis of patterned injuries and injury-causing instruments with forensic 3D/CAD supported photogrammetry (FPHG): an instruction manual for the documentation process.

Forensic 3D/CAD supported photogrammetry (FPHG) is a method of recording and documenting the surface of small objects, thus enabling a three-dimensional image of these objects in virtual space. With this representation on the computer screen the course of forensically relevant events can be reconstructed. The procedure allows for examining patterned injuries of skin, soft tissue or bones for matching potentially incriminated instruments in shape, size and angle.3D recording of objects to be examined requires taking series of photographs. A computer system then calculates the position in space of certain points on the surface of the objects and subsequently produces 3D data models of the objects. Using a 3D/CAD program these data models are used to generate graphic true-to-object volume models. The objects in question can then be moved against each other arbitrarily on the screen-depending on the questions to be answered-in order to compare them and possibly establish their congruence. This article covers the state of the art in FPHG procedures in the form of a step-by-step instruction. It also illustrates the wide range of FPHG applications.

Forensic Medicine↗
PubMed2005

Person identification by gait analysis and photogrammetry.

Surveillance images from a bank robbery were analyzed and compared with images of a suspect. Based on general bodily features, gait and anthropometric measurements, we were able to conclude that one of the perpetrators showed strong resemblance to the suspect. Both exhibited a gait characterized by hyperextension of the leg joints, and bodily measurements did not differ by more than 6 mm on average. The latter was quantified by photogrammetry: i.e., measuring by using images of the perpetrator as captured by surveillance cameras. Using the computer software Photomodeler Pro, synchronous images from different cameras were compared and concurrent body features were identified. The program could then render the perpetrator as a three dimensional, high-precision, scalable and measurable object.

Adult↗
PubMed2004

Three-dimensional point localisation in low-dose X-ray images using stereo-photogrammetry.

A stereo-photogrammetric method for three-dimensional reconstruction of points in low-dose digital X-ray images obtained using a scanner with similar imaging geometry to that of computed tomography scan projection radiography, was analysed. A calibration frame containing 25 radio-opaque markers with known three-dimensional locations was scanned, and the accuracy of reconstruction of the marker positions under varying control point configurations and separation angles was assessed. Errors of less than 1 mm were obtained when nine test points were reconstructed, with 16, 11 and 7 control points at a 90 degrees separation angle, and with 16 and 11 control points at 75 degrees and 60 degrees separation angles. The optimum reconstruction, with a resultant error of 0.68 mm, was found to occur at a separation angle of 90 degrees, with the largest number of control points (16) used to calculate the parameters of the transformation. Extrapolation in the scanning direction beyond the space defined by the control points gave errors of less than 2 mm. This method should be suitable for three-dimensional point reconstruction in applications such as cephalometry, brachytherapy planning and assessment of spinal shape.

Humans↗
PubMed1997

[3-dimensional photogrammetry assessment of facial contours].

In Germany, three-dimensional non-invasive measurement techniques are not in routine use for medical purposes. Completely integrated applications of photogrammetric technology are lacking. The results of clinical examination, X-rays and pre- and postoperative photographs from different angles have been used for medical analysis. In an interdisciplinary research project we tested the general applicability of photogrammetric measurement systems. We examined patients with malformations of the mandible-maxilla complex by taking pictures of the face. In order to assess the surface structure we projected regular patterns onto the surface. We calculated about 500 points on the surface with accuracy better than 0.2 mm. Graphical analyses of measurement results are presented in clinically relevant form. We produce representations of the faces in auto-CAD by means of regular meshes which allow views from any perspective, longitudinal and lateral sections. In addition to calculating angles, distances, surfaces and volumes, visualisation of shape is a useful aid in documentation and quantification of changes of soft tissue of the human face under surgery treatment.

Adult↗
PubMed2003

[Photogrammetry of knee joint kinematics after hinge arthroplasty].

Hinge prostheses are the oldest total knee arthroplasties based on the easiest model of knee joint kinematics. The complex knee joint movement is simplified by a hinge rotating around the flexion-extension axis. Nevertheless, different studies showed that in unscathed joints an instant center pathway in the sagittal plane must be expected. The objective of the current photogrammetric investigation was the assessment of these pathways after hinge arthroplasty. Moreover, they were compared with reference pathways from healthy participants. A total of 20 patients were examined on average 12.1 years after implantation of St. Georg hinge prostheses. Apart from this, 50 test persons with unscathed knee joints were investigated. The examination unit consisted of a standardized chair with passive knee joint movement (90-0 degrees flexion) supported by an electric motor. The position of predefined skin markers was assessed by digital camera with online transmission to a PC. The instant center pathway was then evaluated applying the Reuleaux technique based on the changes of skin marker positions. Patients with hinge prostheses showed small pathways almost comparable to dots. Apart from this, courses of the pathways depended on the extent of soft tissue in the knee joint area. Small values were associated with round or oval courses,whereas increasing soft tissue led to triangular and slightly increased dimensions of the courses. Pathways of the reference participants confirmed this observation and additionally showed clearly greater dimensions of the pathways. The instant center pathway of unscathed knee joints showed a dependence of the course on the extent of soft tissue. The same observation was made in patients with hinge prostheses. Moreover,the latter were characterized by very small, almost fixed pathways. These results confirm the neglect of additional movement components in hinge prostheses.

Adult↗
PubMed1992

Accuracy assessment and control point configuration when using the DLT for photogrammetry.

The direct linear transformation (DLT) is a common technique used to calibrate cameras and subsequently reconstruct points filmed with two or more cameras in a three-dimensional object space. The assessment of the accuracy of this technique, and of the influence of the distribution of control points on accuracy were examined. It was concluded that to obtain a true estimation of reconstruction accuracy, an independent assessment criterion is required, and that the use of control points distributed around the outside, rather than within the space to be calibrated, is preferred.

Calibration↗
PubMed2005

Geodesic photogrammetry for localizing sensor positions in dense-array EEG.

OBJECTIVE: An important goal for functional brain studies using EEG technology is to estimate the location of brain sources that produce the scalp-recorded signals. The accuracy of source estimates is dependent upon many variables, one of which is the accurate description of the scalp positions of the EEG sensors. The objective of the present research was to develop a photogrammatic method for sensor localization that is fast, accurate, and easy to use. METHODS: With the novel photogrammetric method, multiple cameras were arranged in a geodesic array, and images of the sensors on the subject's head were acquired allowing for the reconstruction of the 3D sensor positions. RESULTS: Data from the photogrammetric method were compared with data acquired with the conventional electromagnetic method. The accuracy of the photogrammatic method, quantified as RMS of the measured positions and the actual known positions, was similar (mean error = 1.27 mm) to the electromagnetic method (mean error = 1.02 mm), and both approximated the localization error of the calibration object (mean error = 0.56 mm). CONCLUSIONS: Accurate determination of 3D sensor positions can be accomplished with minimal demands on the time of the subject and the experimenter using the photogrammetric method.

Electrodes↗
PubMed2001

Machine vision photogrammetry: a technique for measurement of microstructural strain in cortical bone.

Understanding local microstructural deformations and strains in cortical bone may lead to a better understanding of cortical bone damage development, fracture, and remodeling. Traditional experimental techniques for measuring deformation and strain do not allow characterization of these quantities at the microstructural level in cortical bone. This study describes a technique based on digital stereoimaging used to measure the microstructural strain fields in cortical bone. The technique allows the measurement of material surface displacements and strains by comparing images acquired from a specimen at two distinct stress states. The accuracy of the system is investigated by analyzing an undeformed image set; the test image is identical to the reference image but translated by a known pixel amount. An increase in the correlation sub-image train parameter results in an increase in displacement measurement accuracy from 0.049 to 0.012 pixels. Errors in strain calculated from the measured displacement field were between 39 and 564 microstrain depending upon the sub-image train size and applied image displacement. The presence of a microcrack in cortical bone results in local strain at the crack tip reaching 0.030 (30,000 microstrain) and 0.010 (10,000 microstrain) near osteocyte lacunae. It is expected that the use of this technique will allow a greater understanding of bone strength and fracture as well as bone mechanotransduction.

Animals↗
PubMed1999

Digital two-dimensional photogrammetry: a comparison of three techniques of obtaining digital photographs.

Three methods of obtaining digital photographs in a clinical setting were compared using direct anthropometry as a reference standard. The methods included a digital camera, scanning negatives from a 35-mm single-lens reflex camera, and scanning Polaroid photographs taken with a Polaroid camera designed for medical documentation. A total of 11 angular and linear anthropometric measurements obtained from 30 healthy volunteers were used for the comparison. The data were analyzed using a variance covariance approach to repeated measures. The analysis revealed that the three cameras were not statistically different from each other. Other advantages and disadvantages, such as cost and ease of use, are discussed.

Adolescent↗