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Results for “Photogrammetry”

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At least 73 records · Page 4Linked to original sources
PubMedDate not supplied

Stereo-photogrammetry for the determination of patient surface geometry.

A stereo-photographic system has been developed with which surface contours of a human subject may be obtained rapidly and objectively. Nonmetric cameras are used and the results are obtained from direct measurements of the photographs. Software has been developed for interpretation of the photographic data with the assistance of a small computer and desk-top digitizer such as those routinely used in radiotherapy treatment planning. With the system the coordinates of a point on the subject may be determined with an accuracy of +/- 1-2 mm.

Computers↗
PubMed1977

The use of photogrammetry in tissue compensator design. Part II: experimental verification of compensator design.

A computer algorithm for designing sheet lead tissue compensators is described. Corrections are made for scatter within the radiation field as well as the shape of the patient for the mantle fields used in treating Hodgkin's disease. The method was tested experimentally with a phantom and found to be clinically acceptable. The advantages of employing this technique with parallel opposed fields are emphasized.

Hodgkin Disease↗
PubMed2001

Micromovements at the aortic aneurysm neck measured during open surgery with close-range photogrammetry: implications for aortic endografts.

PURPOSE: To describe the motion of abdominal aortic aneurysm (AAA) as a first step toward determining if stent-graft migration may be due to propulsive movements at the neck. METHOD: In an initial laboratory validation test, a silicone AAA model was imaged with a stereo-pair configuration of calibrated digital cameras using retro-reflective and ink dot surface targets. This technique was then applied to 4 aneurysm necks imaged at open surgery. In each case the paired images were measured and analyzed to produce sequences of accurate three-dimensional (3-D) surface models of the anterior aspect of the aortic neck. Engineering techniques were used to visualize and identify differences between the generated surfaces, allowing changes in shape of the aortic wall to be determined. RESULTS: The correlation between stereoscopic digital imaging with electronic caliper measurements of linear dimensions was accurate, irrespective of the type of surface targets used (r2 = 0.98). The AAA neck demonstrated complex 3-D movements that ranged from 1.0 to 1.5 mm in the radial direction to 0.6 to 1.0 mm along the longitudinal axis, with a 0.44 to 0.59-mm rotational component (p < 0.05). CONCLUSIONS: This pilot study raises questions about the validity of accepted models of arterial wall movements and compliance in which rotation has not been described. The technique used to measure dynamic neck morphology appears promising as a means to further define the mechanical parameters of the human aorta, which may assist in designing stent-grafts.

Aged↗
PubMedDate not supplied

Photogrammetry--an alternative to conventional impressions in implant dentistry? A clinical pilot study.

PURPOSE: The purpose of this clinical pilot study was to describe a photogrammetric technique to determine implant positions in the oral cavity, and to test and compare this technique to conventional impression/master cast procedures for fabrication of titanium frameworks with a computer numeric-controlled (CNC) milling technique. MATERIALS AND METHODS: Implant positions were recorded by means of conventional impressions/master casts as well as intraoral 3-dimensional photogrammetric measurements in 2 patients who were provided with 5 Brånemark implants each in the edentulous mandible. For each patient 2 titanium frameworks were made by means of a CNC milling technique (All-in-One). Both frameworks had an identical design, but the orientations of the framework cylinder fit surfaces were machined either from measurements from the master casts or from the intraoral photogrammetric measurements. The frameworks were tried for fit in the oral cavity and on the master casts. RESULTS: Both cases showed different precision of fit when comparing the 2 frameworks on the master casts. One of the 2 photogrammetric frameworks was not considered acceptable when tried on the models. In the oral cavity, however, all 4 frameworks presented comparable fit, and all were accepted for clinical use. CONCLUSION: The clinical experiences with try-in of the 4 different frameworks indicated that the photogrammetric technique could be a valid option for conventional impressions when using CNC milling fabrication in implant dentistry. The different results from the model and oral examinations also imply the difficulties of assessing clinical fit when testing fit at the master cast level only.

Computer-Aided Design↗
PubMed1975

[Use of photogrammetry for taking body contours in radiotherapy].

A photogrammetric method for taking outline of patients in radiotherapy is described in details. Using only one couple of photographs, this fast and very precise process may restitute a great deal of transversal or longitudinal cross-sections, even after a long time because photographic stocking of information. An automatic numeric lecture of the outline may directly enter a computer for dosimetry.

Humans↗
PubMed1989

Optic disc photogrammetry: magnification factors for eye position, centration, and ametropias, refractive and axial; and their application in the diagnosis of optic nerve hypoplasia.

To determine if image magnification from ametropia or other factors required correction in the photogrammetric diagnosis of optic nerve hypoplasia, the following variables were studied using two standard 30 degrees field fundus cameras (Zeiss FF-3 and Kowa RC-2): (1) distance between the camera and the subject--variations in this distance do not change the image size; (2) decentration of the camera (i.e., decentration of the optic disc image within the field)--no effect was found using the Kowa camera, but in the Zeiss, a 2% (0.07 mm) increase in disc image size was found for each mm of optic disc decentration in the field; (3) ametropia, refractive experimental (induced in one subject with soft contact lenses, from +8.00 diopters (D) to -8.00D)--no significant change in image size was found (In addition, in 50 healthy adult eyes with various refractive errors, including ten with uncorrected aphakia, there was no significant difference found for the size of the optic nerve in different refractive ametropias. No correction factor was necessary for aphakia or for other refractive ametropias); and (4) ametropia, axial--axial myopia showed minor but significant magnification: a linear increase in the horizontal diameter of the optic disc image of 2% (0.07 mm) was found for each diopter of axial ametropia exceeding 3D. There was insufficient data for axial hyperopia. These magnification factors should be applied when measuring the optic disc on 35-mm transparencies to make a diagnosis of optic nerve hypoplasia.(ABSTRACT TRUNCATED AT 250 WORDS)

Aphakia↗
PubMed1989

[Use of photogrammetry for evaluating the effectiveness of percutaneous transluminal coronary angioplasty].

In 16 patients which underwent PTCA of a right or left coronary artery, analysis of coronarographic image using the stecometer (a precise instrument measuring background coordinates) was performed. Segment of a coronary artery in which PTCA was performed, was estimated in projections: RAO 30 degrees and LAO 60 degrees with a cranial 30 degrees-45 degrees view before and after the procedure. Totally, 72 arteriograms were evaluated. Measurements data were processed by a computer under a written program. Obtained results were presented digitally as a coordinates list and graphically as automatically plotted by Digigraf, drawings in the scale of 10:1 or 20:1. Obtained results were convergent with the hitherto applied method of coronary arteries stenoses approximate assessment.

Angioplasty, Balloon, Coronary↗