[Anticoagulant therapy with i.v. non-fractionated sodium heparin with normogram based on body weight: evaluation of a series of 50 patients with venous thromboembolic disease].
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Aged↗
Biomedical subjects
G Landini
Publications and source records attributed to G Landini.
A testing system for electric toothbrushes.
PURPOSE: To assess in vitro the contributions of mechanical and acoustic microstreaming forces around electric toothbrushes to remove cheese using an experimental model. MATERIALS AND METHODS: Four toothbrushes, Braun Oral-B Plaque Remover (D7), Braun Oral-B Ultra Plaque Remover (D9), Interplak (IP) & Sonicare (SC), were investigated. A model system consisting of a layer of 0.2 mm thick cheese was applied to a microscope slide. The toothbrushes were operated in contact with the slide under loads of 0.3 N dry or with the bristles immersed in 2 mm of water. Turbulence around the moving head was assessed with the bristles placed non-contacting, 1 mm above the slide. An experiment with contact for 2 seconds and then 10 seconds non-contact was also made. The slides were stained and image analyzed. The area of removal was measured together with the "average cleaning/brush contact unit area", (the area of removal was divided by bristle contact area. RESULTS: The removal pattern varied. D9 and SC were efficient when operated dry. When the brushes were operated in water, the D9, SC, and IP were efficient in removing the cheese. With no contact, SC produced disruption of the cheese layer while the other brushes did disturb the surface but did not remove completely the cheese. This disturbance without removal was not recorded by image analysis. When the vibrating brushes were allowed to touch the medium and then moved away, a large amount of removal occurred. Larger amounts of removal took place with the D7, D9 and the SC. The use of brushes with a larger head and bristle contact produced a larger area of removal. However, when the "average cleaning/brush contact unit area" was used, the smaller headed brushes produced a larger amount of removal relative to their size. These differences in the removal characteristics between the four electric toothbrushes in vitro suggest that such a model system may prove useful in testing such devices before they are assessed clinically.
Analysis of Variance↗
Discrimination of complex histopathological tumour profiles by experienced and inexperienced observers.
One of the tasks that pathologists routinely perform in diagnosis is the assessment of complexity of shape or texture of microscopic images. Because some of these complex patterns can be approximated in terms of fractal structures, it is important to understand how fractal structures are perceived by pathologists, and whether pathologists use specific perceptual strategies to quantify such patterns. Knowledge about this could be advantageous for either producing specific training programmes to increase complexity discrimination or to utilise more unbiased and quantitative imaging methodologies in histopathology. We have previously demonstrated that non-expert observers with high abilities in simultaneous information processing were best at the task of discriminating the fractal dimension of self-similar computer-generated curves. Here we compare the performance of experienced and inexperienced observers in a similar task of discriminating epithelial profiles. The results suggest that there are no differences between experienced and inexperienced observers in this task of complex profile discrimination.
Carcinoma, Squamous Cell↗
Is periodontal breakdown a fractal process? Simulations using the Weierstrass-Mandelbrot function.
This paper introduces a theoretical model of periodontal disease that is multifactorial, cumulative and produces periodontal breakdown in "bursts and remissions". The simulation is based on the generalization of the Weierstrass-Mandelbrot function as an integration of a series of sinusoid fluctuations that facilitate or prevent periodontal breakdown with different frequencies, amplitudes and phases. The breakdown is produced when the integration of the factors reaches a certain threshold and is stopped when it is below it. The zeroset of the function (the set of points of the function in intersection with the time axis) is a self-similar set that corresponds to the instances when the process switches between destructive and non-destructive phases, and its fractal nature indicates that in theory, bursts of destruction do not have a characteristic duration size. If the mechanism of periodontal disease has in principle similarities to the model presented, then accurate site-specific predictions about periodontal destruction may prove an unrealizable task.
Alveolar Bone Loss↗
The fractal structure of caries?
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Adolescent↗
How important is tumour shape? Quantification of the epithelial-connective tissue interface in oral lesions using local connected fractal dimension analysis.
Quantification of the local complexity of the epithelial-connective tissue interface (ECTI) in normal mucosa, epithelial dysplasia, and squamous cell carcinoma of the floor of the mouth was investigated by estimating the local connected fractal dimension in tissue profiles from histological sections. The use of certain parameters of the distribution of the local connected fractal dimensions of the ECTI classifies the cases belonging to these three histopathological diagnoses with 85 per cent accuracy by means of linear discriminant analysis. The values of the local fractal dimension were also used to produce colour-coded dimensional images of the ECTI, to highlight locations with higher irregularity that may correlate with locally invasive 'higher-risk' areas.
Carcinoma, Squamous Cell↗
Quantification of nuclear pleomorphism using an asymptotic fractal model.
OBJECTIVE: Nuclear pleomorphism (nuclear membrane irregularity) was investigated using transmission electron microscope (TEM) micrographs of 1,419 nuclei (32 oral carcinomas and normal cells from surgical margins). STUDY DESIGN: Nuclear profiles (1,400 x) were digitized (1 pixel = 35 nm) and fractal dimension estimated using the "yardstick" method. RESULTS: Log-log plots of yardstick length vs. perimeter showed a significant effect on length measurement typical of fractals at low resolutions (large yardsticks), but this effect disappeared at higher resolution (small yardsticks); that is compatible with Rigaut's asymptotic fractal model. Analysis of the asymptotic fractal parameters c, L and Bm showed that c was higher in normal nuclei, but log(L) and Bm were higher in malignant nuclei. A linear discriminant analysis using c, log(L) and Bm reclassified correctly 78.8% of the nuclei (normal 88.0%, tumor 70.2%). CONCLUSION: Asymptotic fractal analysis of nuclear profiles appears to show great potential for quantitative discrimination of oral cancer cell features.
Carcinoma, Squamous Cell↗
Possible mechanism of bacterial invasion based on the concept of percolation in porous media (in this particular case, periodontal tissues)
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Disease Progression↗
Local connected fractal dimensions and lacunarity analyses of 60 degrees fluorescein angiograms.
PURPOSE: The retinal vascular tree exhibits fractal characteristics. These findings relate to the mechanisms involved in the vascularization process and to the objective morphologic characterization of retinal vessels using fractal analysis. Although normal retinas show uniform patterns of blood vessels, in pathologic retinas with central vein or artery occlusions, the patterns are irregular. Because the generalized box fractal dimension fails to differentiate successfully between normal and abnormal retinal vessels in 60 degrees fluorescein angiograms, the authors have further investigated this problem using the local connected fractal dimension (alpha). METHODS: The authors studied 24 digitized 60 degrees fluorescein angiograms of patients with normal retinas and 5 angiograms of patients with central retinal vein or artery occlusion. The pointwise method estimated the local complexity of the angiogram within a finite window centered on those pixels that belong to the retinal vessels. Color-coded dimensional images of the angiograms were constructed by plotting the pixels forming the object with a color that corresponded to specific values of alpha +/- delta alpha. RESULTS: The color-coded representation allowed recognition of areas with increased or decreased local angiogram complexity. The alpha distributions showed differences between normal and pathologic retinas, which overcomes problems encountered when using the methods of calculating the generalized fractal dimensions. A multivariate linear discriminant function using parameters from the alpha distribution and a further fractal parameter--lacunarity--reclassified 23 of the 24 normal and 4 of the 5 pathologic angiograms in their original groups (total: 92.1% correct). CONCLUSIONS: This methodology may be used for automatic detection and objective characterization of local retinal vessel abnormalities.
Discriminant Analysis↗
Fractal geometry in rat chimeras demonstrates that a repetitive cell division program may generate liver parenchyma.
In the development of mammalian organs, a rapid and robust expansion of the parenchymal compartment must occur following allocation of organ primordia. This expansion must be regulated so that sufficient tissue mass is generated for further organization into functional tissues. The discovery that mosaic patches in the liver of rat chimeras are fractal (a geometric form with characteristic complexity) suggests a possible information storage scheme for programs of parenchyma generation. Since fractal objects are produced by the repetitive application of specific rules, it is possible that such a mechanism is responsible for the generation of organ parenchyma. The model cell division program for the generation of organ parenchyma considered here is to choose a cell at random to divide and place the daughter cell in a randomly chosen adjacent position displacing other cells which might occupy the chosen position. The completion of the division creates a new population of cells representing the input conditions for the next division. When this is repeated over and over in a tissue comprising two genetically distinguishable populations of cells, analysis of the geometry of the mosaic pattern obtained should fulfill specific predictions. If cell division occurred in this manner, the complexity of patch boundaries (patches are contiguous aggregates of cells of the same marker lineage in tissue from a chimera) should be independent of the proportion of the two parental cell lineages which make up the chimera's tissue. However, the complexity of the entire patch pattern should be dependent on this proportion. The complexity of the spatial distribution of the patches within a chimera's tissue should also be dependent on the proportion of the two parental lineages. We have measured the complexity of patch boundaries (surface fractal dimension), the complexity of entire fields of patches (mass fractal dimension), and the complexity of the spatial distribution of patches (fractal fragmentation) in rat liver from chimeras. We have established that the surface fractal dimension does not change as the proportion of the two parental lineages in the chimera's tissue changes, that there is a simple relationship between the complexity of entire patches and this proportion, and that the patches are fractally fragmented. These results are consistent with the hypothesis that repetitive application of this simple cell division program accounts for the generation of liver parenchyma.
Animals↗
Notes on the implementation of the mass-radius method of fractal dimension estimation.
The graphical implementation in computers and image analysers of the mass-radius method of fractal dimension estimation has two sources of error. The first is associated with underestimation of area of the 'circle scan' in a square matrix; the second arises from the overestimation of areas at small radii. Methods of coping with these problems are described.
Algorithms↗
Fractal analysis of the normal human retinal fluorescein angiogram.
The fractal dimension of the retinal vasculature and isolated venous and arterial trees down to a caliber of 40 microns was estimated in 23 routine fluorescein angiograms of normal retinas. Fractal dimension was determined with a method based on the box counting theorem. This method is less susceptible to the radial architecture of the retinal vascular tree than those previously reported (mass-radius relation and density-density correlation function). Two scale ranges with different fractal dimension were consistently present. The estimated fractal dimensions showed no significant difference between isolated arterial and venous trees which is not supported by previous reports. This method was designed for simple application in a clinical setting.
Adolescent↗
Size dependent variation in the fractal dimensions of herpes simplex epithelial keratitis.
Dendritic ulcers, the commonest manifestation of herpes simplex epithelial keratitis (HSEK) are fractals. It is likely that their fractal properties alter if they progress to a geographic appearance. This study investigates the relationship of maximum ulcer diameter (Feret's diameter) to area (Dm) and perimeter fractal dimensions (Ds), parameters of the complexity of their areas and outlines respectively. For dendritic ulcers in the size range of 1.6-3.2 mm, Dm = 1.41 +/- 0.06 and Ds = 1.40 +/- 0.04 (mean +/- SD). With increasing ulcer size, a progressive divergence of the values of Dm and Ds occurred, such that values of 1.75 and 1.22 respectively were found at a maximum diameter of 8.4 mm. These results imply that as ulcers enlarge, their outlines become less irregular and they fill more of a 2-dimensional plane. Dm and Ds are useful parameters in quantifying the progression of HSEK from dendritic to amoeboid morphology and could have a role in the assessment of ulcer response to pharmacological intervention. A knowledge of the fractal properties of HSEK may increase understanding of the mechanisms of ulcer formation and viral spread.
Cornea↗
Fractal dimensions of the epithelial-connective tissue interfaces in premalignant and malignant epithelial lesions of the floor of the mouth.
Irregularity of the shape of epithelial-connective tissue interfaces is a well-recognized feature of malignant and premalignant epithelial lesions, yet few attempts have been made to assess it objectively. The fractal dimension (as a measure of irregularity of shape) of the epithelial-connective tissue interface of premalignant, malignant and normal epithelial tissues of the floor of the mouth was measured using box counting and boundary trace methods. The lowest value found was 0.99 (a normal mucosa using the box method) and the highest 1.61 (a carcinoma using the trace method). Analysis of the values against the histopathologic diagnoses (normal, keratosis with mild dysplasia, keratosis with moderate/severe dysplasia and squamous cell carcinoma) showed no significant difference between normal epithelium and that from keratosis with mild dysplasia, but these were significantly different from the two other diagnoses, which were significantly different from each other. The study illustrated the potential of fractal analysis for providing objective diagnostic information about irregular shapes in histopathology.
Carcinoma, Squamous Cell↗
Simulation of corneal neovascularization by inverted diffusion limited aggregation.
PURPOSE: The authors modeled the normally avascular mammalian cornea response to injury by neovascularization. The nature of this process remains obscure, although diffusion mechanisms are thought to be involved. METHODS: Corneal neovascularization was simulated using fractal stochastic computer models for nonequilibrium diffusion (inverted diffusion limited aggregation) and a stochastic ballistic aggregation. RESULTS: The inverted diffusion limited aggregation model was found to generate patterns strikingly similar to those observed in pathologic neovascularization of the cornea in vivo. CONCLUSIONS: This result supports the role of random diffusion mechanisms modified by environmental factors, such as the release of angiogenic factors in corneal angiogenesis.
Computer Simulation↗
Meningioma of the mandible.
This is the first case report to the authors' knowledge of a primary extracranial meningioma located in the mandible. Ultrastructurally, the tumor cells had intricate cellular membranes and desmosome-like attachment structures. Using immunohistochemical analysis, the tumor expressed both epithelial membrane antigen and vimentin. Although the origin of extracranial meningiomas has been attributed to proliferation of ectopic embryonal nests of arachnoidal cells, the proliferation of perineural cells of peripheral nerves also is possible as a result of the structural and functional similarities of perineural cell and arachnoid cells. The authors suggest that extracranial meningiomas may be more common than published reports indicate because of certain histologic similarities between these tumors, neurilemomas, and solitary neurofibromas.
Biomarkers↗