Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Geometric morphometrics”

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 289 records · Page 16Linked to original sources
PubMed1999

Osseo-mechanical induction of extra-cortical plates with reference to their surface properties and geometric designs.

The purpose of this investigation was to determine which geometric and surface properties encouraged optimal ingrowth and bonding of bone to an extra-cortical plate. Forty-eight titanium extra-cortical plates were attached onto the left and right femora of adult rabbits. The plates were of six different designs and the osseoconductive effects of four surfaces were examined. A roughened titanium surface, a plasma sprayed HA coating of low crystallinity (57%) and a solution precipitated calcium phosphate coating were compared with a plasma sprayed crystalline hydroxyapatite coating (crystallinity 85%). Thin sections were prepared by grinding and polishing. Bone formation and the interface around the plates were investigated histologically and computer and morphometric analyses were used to quantify new bone formation, bone apposition onto the plate, bone porosity and the condition of the HA coating. The study found that a hydroxyapatite coating (with the exception of the solution precipitated coating) had significantly greater interfacial contact with bone when compared to a roughened titanium surface, and that significantly more bone attached to a crystalline HA coating compared with the HA coating of lower crystallinity although significantly more bone formed in the vicinity of the lower crystalline HA coating. Differences in the bony reaction induced by the various geometric designs were evident and the optimal plate design requires either holes or slots along its length as this encouraged bone ingrowth into the plate.

Animals↗
PubMed2001

Atherosclerosis in the human common carotid artery. A morphometric study of 31 specimens.

The carotid artery bifurcation is of special interest to both the pathologist because of its frequent atherosclerotic depositions, and to the fluidmechanicist because of its complex flow properties. However, current knowledge is incomplete regarding the level and position of atherosclerotic plaques in the carotid bifurcation and their quantitative correlation with its geometry. The study presented here is intended to fill that knowledge gap and try to quantify the geometrical risk factors. During the post-mortem the arteries were excised and filled with a resin at the proper transmural pressure of 80 mm Hg. Thirty-one vessel casts of the carotid artery from twenty-three autopsied individuals were made. The vessel casts were used to measure several geometrical parameters. After fabrication of the vessel casts each artery was investigated according to pathomorphological procedure. An atherometric system (AS) indicating the level of atherosclerotic lesions was applied. The specimens were divided into three groups according to the level of atherosclerosis. The comparison was made between the level of wall alteration of the main branches of the carotid bifurcation (common, internal and external carotid branch), and between these three groups themselves. Further, we conducted a comparison of the averaged geometric parameters in different groups to define the correlations between atherosclerotic lesions and geometric parameters. The results show that the most advanced lesions (fibrous and severe plaques) with about 70% of all lesions were mainly found in the internal and the external carotid branches, compared with only 25% for the common carotid branch. The comparative analysis showed that a relatively high carotid sinus enlargement of > 1.2 of the common carotid branch diameter is a most significant geometric risk factor among those investigated, whereas there was no correlation between branch angles and atherosclerosis. In conclusion, the quantification of atherosclerotic risk factors is very important in the investigation of atherosclerotic disease development.

Adult↗
PubMed1995

Critique of conceptual basis of diffusing capacity estimates: a finite element analysis.

We present a simple geometric model of a pulmonary capillary segment containing a variable number of red blood cells. The pattern of CO transfer from alveolar air to capillary red blood cells in this model is accurately computed by a finite element method and used to explore conceptual flaws in the Roughton-Forster (RF) and morphometric methods of estimating pulmonary diffusing capacity for CO. The CO uptakes calculated by the finite element method at two alveolar O2 tensions are introduced into the RF model to determine whether the anatomically defined membrane component of diffusing capacity for CO (DmCO) and pulmonary capillary blood volume (Vc) are recovered. The same capillary model is also subjected to standard morphometric analysis. Results are compared at different levels of capillary hematocrit (Hct). The RF method accurately recovers DmCO and Vc at a low Hct but modestly overestimates DmCO and underestimates Vc at higher Hct; errors arise because conductance of the tissue-plasma membrane for CO varies with alveolar O2 tension. The morphometric method seriously overestimates DmCO because the true tissue-plasma resistance to diffusion is underestimated and the effective membrane utilized for diffusion is overestimated; these errors are accentuated by a low Hct.

Animals↗
PubMedDate not supplied

Fractal analysis of placenta mature villi in healthy, smoking and non-smoking women.

Not all the objects created by nature can be described by means of the classical Euclidean geometry rules. New, quickly developing fractal theory can provide another instrument for describing irregular surfaces of e.g. geometric structures and objects whose development results from growth, differentiation and degeneration processes. In the present study we decided to perform fractal analysis of mature, terminal villi of placenta taken from smoking and non-smoking women, during the third trimester of pregnancy. The aim of this study was to find another morphometric parameter, independent of subjective factors, which would provide new information about the studied structure. Placentas were taken from healthy women, untreated primiparas, who did not undergo any hormonal treatment, aged 18 to 27. The material was divided into: control group--placentas from non-smoking women, and two experimental groups--placentas from non-smoking up to 30 cigarettes daily and placentas from women smoking up to 30 cigarettes daily and placentas from women smoking over 30 cigarettes daily. Fractal dimension was determined by three methods: box counting, dilation and mass scaling method. Taking under consideration the results obtained in the present study it seems that fractal dimension, objectively and independently of many factors, allows to perform mathematical estimation of the parameter which is the terminal villi occurrence density within placenta. Among the applied fractal analysis methods, used for placenta terminal villi density grade estimation, the most useful seems to be the box counting method, whereas for estimating villi surface complication--the ratio--mass scaling method. Comparing obtained fractal dimension results, we have found that they increase together with the amount of cigarettes smoked during pregnancy.

Adolescent↗
PubMed1991

Three-dimensional reconstruction from serial sections. V. Calibration of dimensional changes incurred during tissue preparation and data processing.

Three-dimensional (3-D) reconstructions from serial tissue sections produce a table of x, y, z coordinates (i.e., a numerical description of the object) that will support 3-D computer graphics displays and morphometric analyses. While measures such as volume or surface area can be generated interactively, almost instantaneously, they are usually of unknown accuracy due to artifacts that may be introduced at two different stages: (1) tissue shrinkage during dehydration and polymerization of a plastic and compression or expansion during sectioning and mounting and (2) geometric and intensity distortions during image capture and data processing. This paper describes simple methods for (1) introducing fiducials (reference marks) that allow measurement of the net distortion incurred during tissue preparation and (2) estimating the amount of geometric distortion arising during image capture and data processing. Application of these methods showed that the net areal change introduced in dog and sheep hearts during tissue processing amounted to +/- 5%. Apparently, the substantial shrinkage that occurs during tissue processing is largely compensated for by the expansion during tissue sectioning and mounting. The methods described may have application to other semisolid tissues.

Animals↗
PubMed1982

Relevance of morphometric parameters for the classification of normal white blood cells.

An interactive morphometry system (Leitz T.A.S.) was used to extract 39 parameters from 1506 cells of five normal WBC classes. The data set was split in a learning set and a test set, and the value of each single parameter and of combinations of parameters was assessed with the interactive pattern recognition system ISPAHAN. A combination of nine densitogram parameters gave a correct classification in 92.6%; adding four geometrical and seven counting densitogram parameters improved this to 98.5%. It appeared that simple measurements are sufficient for a correct differentiation into the normal white blood cell types. In a pilot study fo 40 normal myeloid bone marrow cells of four classes a correct discrimination between mature and immature cells was reached in 93%. Extraction of parameters with the T.A.S. and their subsequent evaluation with ISPAHAN appeared to be an efficient method of white blood cell classification probably including immature cell types.

Autoanalysis↗
PubMed1998

In vivo morphometry of the lamina cribrosa and its relation to visual field loss in glaucoma.

PURPOSE: The lamina cribrosa has been proposed as a site of origin of the optic nerve damage in glaucoma. The purpose of this study was to investigate, in vivo, the clinical features of the lamina cribrosa pores of glaucomatous patients and to relate their morphometric characteristics to the extent of their visual field loss. METHODS: Images of the internal lamina cribrosa surface of 60 glaucomatous patients and 15 normal subjects were acquired, in vivo, using a scanning laser ophthalmoscope (SLO). A purposely developed technique of image processing was employed to objectively evaluate pore morphometry, with particular regard to their geometrical characteristics (circularity and elongation). Visual function was assessed by automated perimetry (Humphrey Field Analyser). RESULTS: Normal subjects showed approximately round lamina pores. In glaucomatous patients, pores become more elongated and less circular with increasing field loss (p = 0.009 and p < 0.001, respectively). CONCLUSIONS: Scanning laser ophthalmoscopy and a new technique of image processing were employed, for the first time, to the investigation in vivo of the lamina cribrosa of glaucomatous patients, in relation to the extent of visual field loss. The results indicated differences in the lamina cribrosa pore morphometry associated with increasing severity of the disease. These changes may represent the result of compressing and shearing forces applied to the laminar plates.

Adult↗
PubMedDate not supplied

[The growth characteristics of the liver parenchyma in the pre- and postnatal ontogeny of the guinea pig].

The growth dynamics of guinea pig liver parenchyma in prenatal and postnatal ontogeny was investigated with morphometrical and stereological methods. The results show that parenchyma growth in prenatal period is determined by high proliferative activity of prehepatocytes, which sizes remain nearly constant. On the contrary in postnatal period hepatocytes' hypertrophy becomes the main factor of parenchyma growth. The specificity of prenatal liver growth can be determined by a necessity to maintain geometrical stability of its "hemopoietic stroma".

Aging↗
PubMed2001

[Geometrical analysis of benign and malignant breast lesions].

PURPOSE: The aim of this study was to describe a computer-assisted method based on fractal dimension and the coefficient of roundness, two mathematical descriptors of irregularly shaped objects, in order to discriminate benign and malignant mammographic lesions. MATERIAL AND METHODS: Twenty-three digitized mammograms were classified as containing benign lesions (n=12) or as containing malignant lesions (n=11) on the basis of readings by two independent radiologists. Morphometrical and fractal analysis of the breast lesions were automatically performed by a computer-assisted image analysis system. RESULTS: The method shows, for the first time, two parameters that allow the classification of irregularly shaped objects, such as benign and malignant breast lesions. A significant increase was obtained when comparing the fractal dimension and the coefficient of roundness of benign versus malignant mammographic lesions. DISCUSSION AND CONCLUSIONS: Benign and malignant breast lesions are characterized by complex morphologies. Complexity is the main property of all biological systems, including natural and pathological structures. In this study, we showed that fractal geometry allows quantitative measurement of the complex morphology of benign and malignant mammographic lesions. Furthermore, this mathematical approach may be helpful for the study of the non-linear dynamic processes involved in breast carcinogenesis.

Breast Diseases↗
PubMed2002

Some recent advances on the study and understanding of the functional design of the avian lung: morphological and morphometric perspectives.

The small highly aerobic avian species have morphometrically superior lungs while the large flightless ones have less well-refined lungs. Two parabronchial systems, i.e. the paleopulmo and neopulmo, occur in the lungs of relatively advanced birds. Although their evolution and development are not clear, understanding their presence is physiologically important particularly since the air- and blood flow patterns in them are different. Geometrically, the bulk air flow in the parabronchial lumen, i.e. in the longitudinal direction, and the flow of deoxygenated blood from the periphery, i.e. in a centripetal direction, are perpendicularly arranged to produce a cross-current relationship. Functionally, the blood capillaries in the avian lung constitute a multicapillary serial arterialization system. The amount of oxygen and carbon dioxide exchanged arises from many modest transactions that occur where air- and blood capillaries interface along the parabronchial lengths, an additive process that greatly enhances the respiratory efficiency. In some species of birds, an epithelial tumescence occurs at the terminal part of the extrapulmonary primary bronchi (EPPB). The swelling narrows the EPPB, conceivably allowing the shunting of inspired air across the openings of the medioventral secondary bronchi, i.e. inspiratory aerodynamic valving. The defence stratagems in the avian lung differ from those of mammals: fewer surface (free) macrophages (SMs) occur, the epithelial cells that line the atria and infundibula are phagocytic, a large population of subepithelial macrophages is present and pulmonary intravascular macrophages exist. This complex defence inventory may explain the paucity of SMs in the avian lung.

Animals↗
PubMed1989

Step response of lung surface-to-volume ratio by light-scattering stereology.

By means of backscattered light from a pointlike source on the pleural surface, we investigated the dynamic behavior of the surface-to-volume ratio (S/V) in excised dog lobes subjected to small volume steps both in and out on both the inflation and deflation limb of standard pressure-volume maneuvers. The technique utilizes the established correlation of the pattern of backscattered light with morphometric mean linear intercept and is suitable for dynamic studies. We hypothesized that 1) there would be a difference in the timing of stress relaxation or recovery between alveolar septa and the fibromuscular tissue in the alveolar duct that would reveal itself as a temporally changing S/V after a step-volume change and 2) that geometric hysteresis (looping of S/V with volume), as seen with large volume excursion histories, would be similarly present in small tidal volume loops. Our experimental results contradicted both hypotheses. In particular, we found virtually no change in S/V after a step-volume change, even in the presence of substantial stress adaptation. In addition, when geometric hysteresis of small loops was present, it was always in the sense opposite to the geometric hysteresis of large loops. We conclude that 1) there is a functional "matching" of the stress-adaptive timing between alveolar septa and ductal mouths and 2) during small volume looping, the stress hysteresis (looping of stress with volume) in the ductal tissue may be larger than that of the septa, including surface tension.

Animals↗
PubMed1986

Computer-assisted morphometry using video-mixed microscopic images and computer graphics.

A microcomputer system has been developed for collection and analysis of morphometric data from video images of histological sections. Microscopic fields of view are visualized on a video monitor and are overlaid with computer-generated graphics by means of a video mixer. Planimetric data are entered by drawing on a digitizing tablet while observing the drawn image superimposed on the tissue. Programs are available to calculate various geometric parameters, count objects in a field, perform descriptive statistics, and measure volume and surface area of a solid from a series of cross sections. A program for point-counting stereology presents single points for scoring within a user-defined reference area. The potential applications of interactive graphics in morphometry are discussed.

Cell Nucleus↗
PubMed1994

A diameter-based reconstruction of the branching pattern of the human bronchial tree. Part II. Mathematical formulation.

In this paper we present the mathematical details of the diameter-based reconstruction technique used in the companion paper (Phillips et al., 1994 - referred to below as Part I) to analyse the morphometric data of Raabe et al. (1976) on the human bronchial tree. In the first section we outline the technique as applied to the incomplete set of measurements in order to estimate properties of the bronchial tree as a whole; in the second section we consider what form these properties would take if the bronchial tree were geometrically self-similar, as has often been assumed to be approximately the case.

Airway Resistance↗
PubMed2001

Fractal geometric analysis of lung cancer angiogenic patterns.

For medical images, the fractal dimension D may be used as an index of irregularity. The angiogenesis patterns of lung cancer were analysed by means of the perimeter-area and box counting algorithms. The fractal nature of all images in the sense of the perimeter-area method and of 68% images in the sense of the box-counting method suggest the possibility to use the fractal dimension as a new non-morphometric parameter evaluating angiogenic processes in neoplasms.

Adenocarcinoma↗
PubMed1977

Objective identification of cell cycle phases and subphases by automated image analysis.

Frequency distributions of integrated optical density, perimeter, projection, area, form factor, average optical density, and mean dispersion path of nuclear images of Feulgen-stained HeLa S3 cells were obtained by automated image analysis at the base threshold of 0.04 OD. The mean values and standard deviations of these geometric parameters were then computed versus increasing values of threshold (0.08--0.32 OD). There is clear evidence of differential chromatin dispersion and convolution during the cycle of synchronized HeLa S3 cells at different times after selective mitotic detachment. The combination of average OD, form factor, and mean dispersion path at base threshold with the threshold dependence of nuclear morphometric parameters permits objective identification of cell cycle phases and their subphases, by characterizing variations in chromatin geometry within and between phases, regardless of whether DNA content remains constant (early G1, middle G1, late G1), varies only slightly (late G1-early S or late S-G2 transitions), or varies significantly (early S-middle S).

Autoanalysis↗
PubMedDate not supplied

Automated morphometric endothelial analysis combined with video specular microscopy.

Contact and noncontact specular microscopes were tested in combination with a highly sensitive video residual-light camera and with the Kontron IPS (Image Processing System). The video information is recorded with a video recorder or with the IPS frame grabber, a digital image storage system. Examples of experimental and clinical applications are demonstrated. Nine linear and structural parameters are analyzed. Two endothelium-typical parameters are presented, which allow topological as well as hexagonal-specific geometric endothelial single-cell analysis.

Animals↗
PubMed1989

Morphometrical studies of human femoral condyles.

Thirty-six cadaver knees were examined by various morphometrical methods in order to obtain mathematical and graphical data concerning the geometry of the lower end of the femora. It was found that the paramedian sagittal curves represented magnifications of a certain curvature pattern specific to the medial and the lateral femoral condyle. These curves could be expressed mathematically for each condyle. Furthermore, we found dimensional as well as geometrical intervariations between the different size groups in the knee sample. This could serve as an argument for preferring a different design for medial and lateral condyle components in knee prostheses.

Femur↗
PubMed1964

A MORPHOMETRIC STUDY ON THE THICKNESS OF THE PULMONARY AIR-BLOOD BARRIER.

A reliable knowledge of the thickness of the alveolo-capillary "membrane" or air-blood barrier is of physiologic interest since it is intimately related to a quantitative estimation of such functional events as gas diffusion or tissue metabolism in the lung. The characteristic thickness of the air-blood barrier with respect to gas diffusion is its harmonic mean thickness, while the arithmetic mean thickness is related to the mass of tissue building the barrier and consuming oxygen in the lung. Two morphometric methods are proposed by which these two dimensions can be estimated from random measurements in the electron microscope in a reliable, simple, and efficient manner. By applying these methods to three rat lungs the arithmetic mean thickness of the barrier was found to measure 1.25 micro, the harmonic mean thickness, 0.57 micro. On the basis of these measurements a geometric model of the barrier in the form of a corrugated membrane was derived. Its dimensions showed close similarity to those of the natural barrier. This analysis suggested furthermore that the gas conductance of the barrier is nearly optimal if one considers the mass of tissue and the minimal barrier thickness as fixed properties which are determined by other functional requirements on the alveolo-capillary membrane.

Blood-Air Barrier↗