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At least 415 records · Page 23Linked to original sources
PubMed1996

Quantification of facial morphology using stereophotogrammetry--demonstration of a new concept.

OBJECTIVES: The purpose of this study was to introduce stereophotogrammetry as a three-dimensional registration method for quantifying facial morphology and detecting changes in facial morphology during growth and development. METHODS: Using stereophotogrammetry, three-dimensional (3-D) co-ordinates for the bilateral landmarks Exocanthion and Cheilion and the midsagittal landmark Pronasale were determined in 10 subjects to ascertain the reproducibility of the method, and in 59 children to detect changes in facial morphology due to growth and development. Linear and angular measurements were calculated by means of the 3-D co-ordinates in order to quantify facial morphology. Significant differences were determined by means of analyses of variance (MANOVA). RESULTS: During the observation period, significant (P < 0.01) changes in facial morphology were determined for the linear measurements. Advantages and disadvantages of current registration methods are discussed. CONCLUSION: It is concluded that stereophotogrammetry is a suitable 3-D registration method for quantifying and detecting developmental changes in facial morphology.

Analysis of Variance↗
PubMed1995

The quantitation of altered hepatic foci during multistage hepatocarcinogenesis in the rat: transforming growth factor alpha expression as a marker for the stage of progression.

The experimental three-stage hepatocarcinogenesis protocol of initiation, promotion, and progression, coupled with the analytical technique of stereology, permits quantitative analysis of the carcinogenic process, including the derivation of biologically based risk assessment models. The aberrant expression of the placental isozyme of glutathione S-transferase (PGST) is an efficient marker for initiated, preneoplastic, and neoplastic hepatocytes. Putatively initiated cells and their clonal progeny can be identified, enumerated, and their growth characteristics determined on the basis of their aberrant expression of this protein. A lack of suitable markers has made the identification and quantitation of hepatocytes in the early stage of progression more difficult. One characteristic of cells in the stage of progression is the evolution of relatively autonomous growth. The alteration of growth factor signalling pathways may provide one mechanism for this observation. The expression of transforming growth factor alpha (TGF alpha) is seen in many malignancies. The initiation-promotion-progression protocol has been used to induce progression in the rat liver. The focal expression of TGF alpha was found to correlate with areas of progression in rats subjected to this protocol. The ability to identify and quantitate cells in the stage of progression should facilitate application of the Moolgavkar-Venzon-Knudson model for assessing human risk from carcinogens active at each of these three stages. Validation of this model will require determination of the number and growth characteristics of hepatocytes in the stage of progression.

Animals↗
PubMed1994

Quantitative analysis of immunohistochemical distributions of cholinergic and catecholaminergic systems in the human brain.

The distributions of the cholinergic system and catecholaminergic system in the normal human brain were analysed quantitatively by a microphotometry system. Consecutive coronal sections were obtained from the anterior area of the left hemisphere and were stained alternately with fluorescent immunohistochemical staining for choline acetyltransferase or tyrosine hydroxylase. Each stained section was divided into approximately 120,000 areas and the fluorescence intensity in each area was measured by a fluorescence microphotometry system which is a measuring microscope for distribution of fluorescence intensity in the tissue slice. Nonspecific autofluorescence was distributed in myelinated nerve fiber throughout the entire area, which was subtracted from the fluorescence intensity value in each measuring area. The obtained immunohistochemical fluorescence intensities of choline acetyltransferase and tyrosine hydroxylase were classified into eight ranks and were indicated by color graphics. Also, the intensity values of actual immunohistochemical fluorescence in the various brain regions were presented. The choline acetyltransferase and tyrosine hydroxylase concentrations varied greatly depending on the brain region. Relatively high levels of choline acetyltransferase and tyrosine hydroxylase were distributed in the putamen, caudate nucleus, claustrum, insula and some cortical regions. The immunohistochemical level of tyrosine hydroxylase was lower than that of choline acetyltransferase in a few brain regions such as the globus pallidus and amygdala. High levels of choline acetyltransferase and tyrosine hydroxylase were localized in the one area of the basal ganglia which developed from the telencephalic area, whereas middle levels of these were distributed in another, part of which developed from the diencephalic area.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylcholine↗
PubMed1991

Tendon excursion and dehiscence during early controlled mobilization after flexor tendon repair in zone II: an x-ray stereophotogrammetric analysis.

The effect of different methods on early controlled mobilization of the flexor profundus tendon regarding tendon excursion and dehiscence was examined during treatment of 20 tendons in 18 patients. An application of radiographic stereophotogrammetric analysis on movements of tendon tissue was developed and the tendons studied during the early postoperative period. Considerable differences of tendon excursion were found between the various mobilization methods and were dependent on the level of injury within zone II. The use of a mobilization method that includes a component of controlled active flexion is suggested for injuries at the A3 and A4 levels. This radiographic stereophotogrammetric analysis method developed for tendon excursion and dehiscence is new and provides knowledge that cannot be obtained in any other way.

Adolescent↗
PubMed1992

Measurement accuracy in acetabular cup migration. A comparison of four radiologic methods versus roentgen stereophotogrammetric analysis.

Four different methods of radiologic evaluation of the acetabular component migration following total hip arthroplasty have been compared with roentgen stereophotogrammetry, a proven highly accurate method for studying early migration. In the Sutherland and Wetherell method the implant's position is measured with a pencil and a ruler from an ordinary pelvis radiograph. New reference lines of the Wetherell method are thought to be more accurate. The Sulzer and EBRA methods are computerized. In the Sulzer method prominent bone markers are digitized and used as reference points. In the EBRA method a system of tangents on prominent pelvis structure is digitized and used to detect radiographs with similar projection. The implant's position is calculated as the mean position of similar radiographs. The Sutherland, Wetherell, and Sulzer methods had almost the same accuracy, whereas the EBRA method was more accurate and could be used for pro- and retrospective studies in a large number of patients.

Acetabulum↗
PubMed1992

Subsidence of porous coated noncemented femoral components in total hip arthroplasty. A roentgen stereophotogrammetric analysis.

Roentgen stereophotogrammetric analysis was used in the evaluation of subsidence in nine noncemented femoral components of the Biomet Taperloc prosthesis. After 2 years three components had subsided 0.7-0.9 mm. No distinct symptoms related to the micromotion appeared. The subsidence in this investigation was smaller than the reported subsidence of other noncemented prostheses.

Adult↗
PubMed1994

Clinical and roentgenographic evaluation of hydroxyapatite-augmented and nonaugmented porous total hip arthroplasty.

Sixty osteoarthritic patients undergoing primary, uncemented total hip arthroplasty were matched for age and weight and randomized into one of four groups with respect to implant coating and postoperative, protected weight-bearing status: group 1, hydroxyapatite-augmented, 12 weeks; group 2, nonaugmented, 12 weeks; group 3, hydroxyapatite-augmented, 6 weeks; and group 4, nonaugmented, 6 weeks. Tantalum spheres were implanted periprosthetically into the femur at the time of the arthroplasty, thus providing constant references for stereoscopic radiographs. Patients were then evaluated over a 2-year period with clinical examination, plain radiography, and roentgen stereophotogrammetric analysis. Clinical evaluation using the Charnley scoring system showed no significant preoperative or postoperative intergroup differences, whereas visual analog testing noted less thigh pain with hydroxyapatite-augmented stems at the 12-week and 6-month follow-up evaluations. Plain radiographic analysis produced no significant differences, with no instability detected, and bony ingrowth was uniform in all groups. Stereographic evaluation showed migration in all groups, but there were no significant differences between the augmented and nonaugmented stems or the 6-week and 12-week partial weight-bearing protocols. Charnley, plain radiographic, and stereogrammetric evaluations all suggest that migration is unaltered by enhanced surfaces and early, unprotected weight bearing does not jeopardize implant fixation regardless of coating design. The lower incidence of visual analog thigh pain with the hydroxyapatite-augmented stems, however, may be a reflection of bony ingrowth and, as such, add some validity to the theoretic advantages of enhanced surface prostheses.

Age Factors↗
PubMed1989

Stereophotogrammetric study of growth and development of the nose.

A total of 269 contour maps of the face were measured in three dimensions to study growth and development of the nose. The maps were derived from a mixed longitudinal study of 26 boys and 26 girls between the ages of 9 and 16 years, and were recorded annually. Various nasal parameters were measured to study growth of linear parameters and external nasal volume. Apart from dorsum of the nose between 9 and 11 years of age, all linear parameters were larger for boys by an amount increasing with age. The early growth in girls and late growth in boys suggested the presence of an adolescent growth spurt in the nose, which was confirmed by volumetric measurements. Developmentally the greatest change occurred in anteroposterior prominence of nasal tip in both sexes and the least change occurred in intercanthal width.

Adolescent↗
PubMed1989

Computer-assisted location of reference points in three dimensions for radiographic cephalometry.

A major obstacle to the derivation of three-dimensional data from lateral and coronal radiographs of the head has been the lack of precision in locating the same landmarks on each of the biplanar images. The method described herein uses radiographic equations based on the geometry of a biplanar system to predict the location of a reference point on one film from its location on the other. This technique, which differs from previously described systems, allows a pair of cephalometric films to be digitized by an on-line procedure controlled by a personal computer. Three-dimensional coordinates of reference points are calculated and stored for subsequent retrieval when they can be used for metric analysis or for the display of simple wire-frame models of the skull. Computing algorithms are provided to aid software development.

Algorithms↗
PubMed1993

Palatal measurements of prematurely born, very low birth weight infants: comparison of three methods.

To enable investigation of palatal changes in infants who are prematurely born, it is necessary to first establish a reliable method of measurement of these tiny edentulous palates. This study compared the Olivetti-Inspector machine, Vernier calipers, and stereophotogrammetry for this purpose. Measurements were taken of 12 palatal casts of four infants at prescribed time intervals during the neonatal period. In each of the three methods, measurements were recorded as variables generated in the X and Z axes of the Cartesian scale in relation to three specified points along the Y axis. The results revealed that all methods were comparable, but the Vernier calipers differed significantly from the other two methods in height measurements, (p < 0.001). It was also found that both the Olivetti-Inspector machine and the Vernier calipers consistently underestimated the width, compared with Olivetti-Inspector machine, (p < 0.05). Stereophotogrammetry was found to be the most consistent method of measuring the configuration of preterm infant palates.

Calibration↗
PubMedDate not supplied

A method for the quantification of the size of liver metastases.

A method for the quantification of the size of liver metastases based on stereologic principles is presented. This evaluation procedure was applied retrospectively to routine computerized tomography (CT) scans of the liver and allowed reliable estimation of the volume of liver metastases. Furthermore, the data were used to create three-dimensional (3D) representations of the examined organ by computer reconstruction.

Adult↗
PubMed2005

Stereo CT image compositing methods for lung nodule detection and characterization.

RATIONALE AND OBJECTIVES: Stereographic display has been proposed as a possible method of improving performance in reading computed tomographic (CT) examinations acquired for lung cancer screening. Optimizing such displays is important given the large volume of image data that must be evaluated for each of these examinations. This study is designed to explore certain tradeoffs between rendering methods designed for the stereo display of CT images. MATERIALS AND METHODS: Stereo CT image compositing methods, including distance-weighted averaging, distance-weighted maximum intensity projection (MIP), and conventional MIP, were applied to lung CT images and compared for lung nodule detection and characterization. RESULTS: Using the Jonckheere test indicated a statistically significant (P < .01) increase in contrast among the three compositing methods. Wilcoxon-Mann-Whitney test showed significant differences in contrast between distance-weighted averaging and conventional MIP (P < .01) and between averaging and distance-weighted MIP (P < .05), but not between distance-weighted MIP and conventional MIP (P > .05). Conventional MIP compositing provided the highest image contrast, but produced ambiguities in local geometric detail and texture, whereas averaging resulted in the lowest contrast, but preserved geometric detail. Distance-weighted MIP partially recovered geometric information, which was lost in images composited by means of conventional MIP. CONCLUSION: Our results indicate that distance-weighted MIP may be a better choice for nodule detection in stereo lung CT images for its high local contrast and partial preservation of geometric information, whereas compositing by means of distance-weighted averaging is preferable for nodule characterization. The relative clinical value of these compositing methods needs to be evaluated further.

Algorithms↗
PubMed2005

Three-dimensional computer-generated head model reconstructed from cephalograms, facial photographs, and dental cast models.

PURPOSE: Three-dimensional (3D) computer models of the human craniofacial structure have been constructed with computed tomography (CT). However, the high cost of CT and the radiation exposure are drawbacks to this method. Attempts to create a 3D reconstruction from lateral and frontal cephalograms have failed because of problems with magnification, distortion, and limitations of landmark identification, among others. We introduce a new method that creates a standard head model for a patient from anatomic measurement points extracted from x-ray images, facial stereo photographs, and dental casts. MATERIAL: To obtain precise 3D coordinates from cephalograms, several equations were introduced to compensate for radiographic image magnification and distortion. RESULTS: By comparing the constructed model and 3D-CT images, this method proved to be accurate. CONCLUSIONS: It is possible to produce a 3D head model on a personal computer and to view it from any desired angle; this will provide easy-to-understand information for patients and establish a diagnostic or therapeutic method for communication with other health care providers.

Adult↗
PubMed2004

The initial stability of an exeter femoral stem after impaction bone grafting in combination with segmental defect reconstruction.

Bone impaction grafting of the femur is associated with more complications when segmental defects are present. The effect of segmental defect repair on initial stem stability was studied in an in vitro study with fresh-frozen goat femora. A standardized medial segmental defect was reconstructed using a cortical strut or a metal mesh. As controls, we used intact femora and femora with a nonreconstructed defect. In all 4 groups, impacted bone grafting was performed in combination with a cemented Exeter stem. Each group contained 5 femora. Reconstructions were dynamically loaded up to 1,500 N. Migration was measured with Roentgen stereophotogrammetric analysis. All cases with a nonreconstructed segmental defect failed into excessive varus rotation. None of the femora with a reconstructed defect failed. Cortical struts and metal meshes were equally effective in creating a stable stem construction (varus rotation, 2.89 +/- 2.27 and 2.27 +/- 0.57, respectively). Reconstructions with a metal mesh were more reproducible, although the obtained stability was significantly lower (P<.01) when compared with impaction grafting in an intact femur (varus rotation, 0.58 +/- 0.36).

Animals↗
PubMed2004

The stability of the cemented tibial component of total knee arthroplasty: posterior cruciate-retaining versus posterior-stabilized design.

Micromotion of the tibial component in 40 knee arthroplasties for gonarthrosis was studied using Roentgen stereophotogrammetric analysis. The stability of this component was assessed for 2 years' postoperatively. In all arthroplasties, an attempt was made to reconstruct the preoperative posterior slope. Posterior cruciate-retaining (CR) and posterior-stabilized (PS) components showed at 2 years a maximum total point motion of 0.6 +/- 0.4 mm and 0.7 +/- 0.5 mm, respectively. Whereas 92.5% of the implants were determined to be stable, 1 of the CR group and 2 of the PS group displayed migration between the first and the second year of at least 0.2 mm. A negative correlation between subsidence of the tibial component at 2 years of follow-up and the difference between preoperative and postoperative tibial slope was found. Consequently, we suggest that restoring the original posterior slope of the tibial plateau must be a goal of tibial component implantation.

Aged↗
PubMed2004

Roll-over shapes of human locomotor systems: effects of walking speed.

OBJECTIVE: To examine the hypothesis that roll-over shapes of non-disabled lower limb systems do not change appreciably with walking speed. DESIGN: Repeated measures (n = 24). BACKGROUND: Roll-over shapes of three lower limb systems are presented. They are: roll-over shapes of the (1) foot, (2) ankle-foot, and (3) knee-ankle-foot systems. Roll-over shapes show the effective rocker (or cam) shapes that the lower limb systems conform to during the period in the stance phase of walking between heel contact and opposite heel contact. METHODS: Roll-over shapes were measured by transforming center of pressure data from a laboratory-based coordinate system into each of three body-based coordinate systems. Knee-ankle-foot roll-over shapes were further characterized using a circular arc model. RESULTS: From a statistical standpoint, the radii of the best-fit circular arcs did not change significantly with walking speed, while the forward shifts of the circular models did change significantly. However, the change in forward shift was not considered to be clinically significant. CONCLUSIONS: The biologic systems involved in developing the roll-over shapes adapt to changing conditions of walking speed, including increased loading amplitudes as speed is increased, to maintain similar effective roll-over geometries. RELEVANCE: Roll-over shapes provide insight into the workings of various lower limb systems by taking a new look at existing gait data. This insight could provide broad utility, helping to develop a better understanding of able-bodied and disabled human walking, and leading to the design of improved rehabilitation devices, surgeries, and therapies.

Adult↗