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At least 1,045 records · Page 58Linked to original sources
PubMed2002

A description of the motion of the navicular bone during in vitro vertical loading of the equine forelimb.

Motion of the navicular bone might play a role in the development of navicular disease in horses but is difficult to asses. In the present study, 3-dimensional motion of this bone was determined using roentgen stereophotogrammetric analysis. Tantalum pellets were inserted, in vitro, in the bones of 6 forelimbs of mature Shetland ponies and kinematics were measured during vertical loading up to 2 kN. The motions of the navicular bone and coffin joint were limited to flexion/extension, there were no substantial out-of-plane motions. There was only little flexion between the navicular bone and the coffin bone, which was correlated (r = 0.66) with coffin joint flexion. There was substantial flexion between the navicular bone and the short pastern, which was highly correlated with coffin joint flexion (r = 0.97). We conclude that the navicular bone, generally, follows the coffin bone during coffin joint flexion, although there are small but consistent motions between the navicular bone and the coffin bone. These motions might play a role in the development of navicular disease in horses.

Animals↗
PubMed1978

Powder data file as a tool for identification of dental gold alloys.

In order to obtain data for a prospective powder data file for dental gold alloys X-ray diffraction photograms of 75 different gold alloys were taken using a Guinier-Hägg camera and CuKalpha1 radiation. Before the X-ray photograms were taken the alloys had been heat treated at 700 degrees C, 800 degrees C or 900 degrees C depending on the solidus temperatures of the alloys. The lattice parameters of the samples were determined from the X-ray photograms. These data were supplemented by a specification of the interplanar spacings of the three strongest lines on the diffraction patterns and also by the relative intensities and Miller indices of these lines. An extensive library of reference films is to be collected and this and other details of the file are discussed. It is not intended that the file be used to identify a particular alloy but merely to identify the type of alloy. Thus it can serve as a guide to facilitate the proper selection of gold alloys within practical clinical dentistry.

Filing↗
PubMed1995

Computer-assisted image processing for quantitative measurements of fractional bone area. A methodologic study.

The purpose of this study was to evaluate a method for computer-assisted image processing to assess quantitatively fractional bone volume in sections of bone biopsies (part I). A second purpose was to apply this method in an experimental study to determine bone loss by measuring fractional bone area in sections of calvarial bone of gastrectomized rats and to compare this with a control group. Stained paraffin sections of skull bone of young rabbits (part I) and rats (part II) were examined. The histologic sections were placed on a microscope. A video camera was connected to the microscope, and the image transferred to a display monitor connected to a PC with dedicated software, performing the measurements. In the first part of the study tests of the reproducibility of the method were performed. The influence of factors such as external illumination and light intensity in the microscope was evaluated by measuring the same area several times at different times (= different illumination) and at different microscope light intensity levels. The automatic method was compared with a manual method, using a Merz grid but automatically calculated. The difference between the means of the manual and automatic measurements was determined with the paired t test. In the second part of the study the unpaired t test was used to determine the differences between the control group and experimental group, both for the manually and the automatically measured values.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Accuracy and reproducibility of KeraScanner analysis in PERK corneal topography. PERK Study Group.

The measurement of the corneal radius of curvature centrally and in the corneal periphery is exceedingly difficult because of variables in photography and data acquisition. We present a technique of Automated image scanning of corneal photographs which provides a more accurate and reproducible analysis of the paracentral corneal contour. We analyzed the sources of error of corneal topography measurement. CorneaScope photographs of calibration balls were generated by each Prospective Evaluation of Radial Keratotomy (PERK) Surgical Center. The 90% confidence intervals for individual ring-radial positions on the 8.00 and 10.00 mm balls were 7.91 to 8.09 mm and 9.89 to 10.11 mm respectively. Our isopter method of analysis for clinical comparison averages all eight radii of curvature for each CorneaScopef ring. This isopter technique reduces the corresponding 90% confidence intervals to 7.96 to 8.03 and 9.95 to 10.06 mm. The measurement variability of a 10 mm calibration ball decreased in the following order: calibration ball positioning, scanner personnel, photograph movement between scans, and nonrepositioned scanning. Photographs of calibration balls demonstrate +/- 4 microns of measurement resolution and patient corneal photographs may be evaluated to +/- 40 microns. This automated scanning system provides consistent data when digitizing keratographs.

Biometry↗
PubMed1992

Accuracy of the Nunn method in measuring acetabular cup migration.

The accuracy of the Nunn method in measuring acetabular component migration was compared with 3 other radiological methods and with roentgen stereophotogrammetry in 34 pelvic radiographs. The Nunn method seems to have the same or better accuracy than the other non-computerized methods, but less accuracy than the computerized EBRA method.

Acetabulum↗
PubMed1982

Angular displacements in the upper body of AK amputees during level walking.

The angular displacements of the longitudinal axis of the trunk, and of the latero-lateral axes of pelvis and shoulder girdle were measured in five normal subjects and four AK amputees during level walking at different speeds. Amputees used single axis prostheses with the SACH foot. Spatial measurements were carried out in three dimensions by means of a photogrammetric technique. The time functions of the target angles underwent harmonic analysis. Based on the Fourier coefficients, comparison was made between normal subjects' and amputees' angular displacements. Relevant findings permitted the identification of compensatory mechanisms adopted by amputees at trunk level as well as the assessment of the relationship between these latter mechanisms and those put into action at lower limb level.

Amputation, Surgical↗
PubMed1985

Physical ability in relation to anthropometric measurements in persons with complete spinal cord lesion below the sixth cervical segment.

A study was undertaken to determine the ability of patients with complete tetraplegia below cervical sixth segment to transfer in relation to their anthropometric characteristics. Thirty-six chronic patients were assessed and spasticity was measured. A discriminant function analysis was carried out to assess the extent to which a number of anthropometric and anatomical variables could predict the patients' final ability to effect a transfer. Using nine of the original 23 predictor variables it is possible to correctly classify a patient's eventual ability to transfer in 92% of cases.

Adolescent↗
PubMed2003

The use of rapid prototyping in the preoperative planning of distraction osteogenesis of the cranio-maxillofacial skeleton.

OBJECTIVE: In cranio-maxillofacial surgery, the principle of distraction osteogenesis (DO) can be used for the reconstruction of the deformed skull, midface complex, mandible and alveolar ridge. Optimal results can only be obtained with accurate planning of the osteotomies and accurate positioning of the distraction device. In addition, the surgical planning must be transferred very precisely to the patient in the operating theater. The clinical accuracy and utility of stereolithographic models in cranio-maxillofacial distraction osteogenesis of the midface, mandible and alveolar ridge will be demonstrated. MATERIALS AND METHODS: Thirteen patients were treated by DO in the cranio-maxillofacial skeleton. Five patients suffered from midface retrusion and were treated by a LeFort III advancement. One patient suffered from an aseptic necrosis of the condylar process of the mandible and had a reconstruction of the condylar process by DO. Seven patients underwent an osteotomy of the alveolar ridge of the mandible with subsequent placement of distraction screws and implants because of advanced atrophy of the mandible. Following preoperative acquisition and conversion of the CT-scan data, a model was fabricated by stereolithography (SLA). Simulation of the osteotomies and placement of distraction devices was performed on these models, then surgical guides were used to transfer the surgical planning to the patient in the operating theater. Pre- and postoperative facial photographs and X-rays were compared to evaluate the accuracy of the transfer procedure. RESULTS: In all cases, matching of pre- and postoperative facial photographs and X-rays showed reconstruction of the bony structures to be as accurate as planned on the SLA models. Transfer of the surgical plan by means of custom-made surgical guides was optimal in all cases. CONCLUSION: Preoperative planning of distraction osteogenesis of the cranio-maxillofacial skeleton and transfer to the operating theater by custom-made surgical guides remains the standard procedure for the planning of complex distraction cases. However, improvements in surgical simulation software and accurate virtual-reality surgery will probably make the use of these models redundant in the future.

Adolescent↗
PubMed2006

Gaze-contingent control for minimally invasive robotic surgery.

OBJECTIVE: Recovering tissue depth and deformation during robotically assisted minimally invasive procedures is an important step towards motion compensation, stabilization and co-registration with preoperative data. This work demonstrates that eye gaze derived from binocular eye tracking can be effectively used to recover 3D motion and deformation of the soft tissue. METHODS: A binocular eye-tracking device was integrated into the stereoscopic surgical console. After calibration, the 3D fixation point of the participating subjects could be accurately resolved in real time. A CT-scanned phantom heart model was used to demonstrate the accuracy of gaze-contingent depth extraction and motion stabilization of the soft tissue. The dynamic response of the oculomotor system was assessed with the proposed framework by using autoregressive modeling techniques. In vivo data were also used to perform gaze-contingent decoupling of cardiac and respiratory motion. RESULTS: Depth reconstruction, deformation tracking, and motion stabilization of the soft tissue were possible with binocular eye tracking. The dynamic response of the oculomotor system was able to cope with frequencies likely to occur under most routine minimally invasive surgical operations. CONCLUSION: The proposed framework presents a novel approach towards the tight integration of a human and a surgical robot where interaction in response to sensing is required to be under the control of the operating surgeon.

Algorithms↗
PubMedDate not supplied

Evaluation of a CCD-based facial measurement system.

This paper describes the configuration and evaluation of a CCD-based biostereometric system at the Department of Orthodontics, Kings College Dental Hospital, London. The system has been designed to allow rapid and accurate measurement of facial soft-tissue shape with a minimum of traditional photogrammetric training. This has been achieved by automatic camera calibration and stereo matching, performed on a Sun Microsystem 3/160 workstation. In summary, the characteristics of the system are: (a) non-contract three-dimensional (3D) measurement of soft-tissue; (b) de-skilled, requiring little or no photogrammetric training; (c) rapid data acquisition, combined with slower off-line processing; (d) processing of resulting 3D surface information to yield cross-sections; (e) surface measurement accurate to within 0.5 mm. Accuracy assessment was performed using a manual electromechanical non-contact measurement device with precision exceeding the requirement of the biostereometric system.

Anthropometry↗