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Thickness Values (thickness + value)
Selected AbstractsQuantifying sediment storage in a high alpine valley (Turtmanntal, Switzerland)EARTH SURFACE PROCESSES AND LANDFORMS, Issue 13 2009Jan-Christoph Otto Abstract The determination of sediment storage is a critical parameter in sediment budget analyses. But, in many sediment budget studies the quantification of magnitude and time-scale of sediment storage is still the weakest part and often relies on crude estimations only, especially in large drainage basins (>100,km2). We present a new approach to storage quantification in a meso-scale alpine catchment of the Swiss Alps (Turtmann Valley, 110,km2). The quantification of depositional volumes was performed by combining geophysical surveys and geographic information system (GIS) modelling techniques. Mean thickness values of each landform type calculated from these data was used to estimate the sediment volume in the hanging valleys and the trough slopes. Sediment volume of the remaining subsystems was determined by modelling an assumed parabolic bedrock surface using digital elevation model (DEM) data. A total sediment volume of 781·3×106,1005·7×106,m3 is deposited in the Turtmann Valley. Over 60% of this volume is stored in the 13 hanging valleys. Moraine landforms contain over 60% of the deposits in the hanging valleys followed by sediment stored on slopes (20%) and rock glaciers (15%). For the first time, a detailed quantification of different storage types was achieved in a catchment of this size. Sediment volumes have been used to calculate mean denudation rates for the different processes ranging from 0·1 to 2·6,mm/a based on a time span of 10,ka. As the quantification approach includes a number of assumptions and various sources of error the values given represent the order of magnitude of sediment storage that has to be expected in a catchment of this size. Copyright © 2009 John Wiley & Sons, Ltd. [source] Functional consequences of cartilage degeneration in the equine metacarpophalangeal joint: quantitative assessment of cartilage stiffnessEQUINE VETERINARY JOURNAL, Issue 5 2005H. BROMMER Summary Reasons for performing study: No quantitative data currently exist on the relationship of the occurrence of cartilage degeneration and changes in site-specific biomechanical properties in the metacarpophalangeal (MCP) joint in the horse. Objectives: To gain insight into the biomechanical consequences of cartilage deterioration at 2 differently loaded sites on the proximal articular surface of the proximal phalanx (P1). Hypothesis: Static and dynamic stiffness of articular cartilage decreases significantly in degenerated cartilage. Methods: Cartilage degeneration index (CDI) values were measured at the lateral dorsal margin (Site 1), lateral central fovea (Site 2) and entire joint surface of P1 (CDIP1) in 30 horses. Group 1 contained joints without (CDIP1 values <25%, n = 22) and Group 2 joints with (CDIP1 values >25%, n = 8) signs of cartilage degeneration. Cartilage thickness at Sites 1 and 2 was measured using ultrasonic and needle-probe techniques. Osteochondral plugs were drilled out from Sites 1 and 2 and subsequently tested biomechanically in indentation geometry. Young's modulus at equilibrium and dynamic modulus were determined. Results: Cartilage thickness values were not significantly different between the 2 groups and sites. Young's modulus at Site 1 was significantly higher in Group 1 than in Group 2; at Site 2, the difference was not significant. Dynamic modulus values were significantly higher in Group 1 than in Group 2 at both sites. Conclusions: Degenerative cartilage changes are clearly related to loss of stiffness of the tissue. Absolute changes in cartilage integrity in terms of CDI are greatest at the joint margin, but concomitant changes are also present at the centre, with a comparable decrease of the biomechanical moduli at the 2 sites. Therefore, significant cartilage degradation at the joint margin not only reflects local deterioration of biomechanical properties, but is also indicative of the functional quality in the centre. Potential relevance: These findings may be important for improving prognostication and developing preventative measures. [source] Micromechanical behavior related to the nanostructure of biodegradable polyestersJOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2010M. E. Cagiao Abstract The microhardness of a series of biodegradable polyesters was determined. The nanostructural features of these materials were studied by wide-angle X-ray scattering (WAXS), small-angle X-ray scattering (SAXS), and differential scanning calorimetry. Analysis of the SAXS and WAXS patterns allowed direct derivation of the degree of crystallinity and crystal thickness values, and correlations of the micromechanical properties are presented. The differences in the thermal and mechanical properties exhibited by the studied systems and the ones found in other aromatic polyesters are explained as due to the different chemical natures of the monomeric units. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] In Vivo Determination of Bone Structure in Postmenopausal Women: A Comparison of HR-pQCT and High-Field MR Imaging,JOURNAL OF BONE AND MINERAL RESEARCH, Issue 4 2008Galateia J Kazakia PhD Abstract Bone structural measures obtained by two noninvasive imaging tools,3T MRI and HR-pQCT,were compared. Significant but moderate correlations and 2- to 4-fold discrepancies in parameter values were detected, suggesting that differences in acquisition and analysis must be considered when interpreting data from these imaging modalities. Introduction: High-field MRI and high resolution (HR)-pQCT are currently being used in longitudinal bone structure studies. Substantial differences in acquisition and analysis between these modalities may influence the quantitative data produced and could potentially influence clinical decisions based on their results. Our goal was to compare trabecular and cortical bone structural measures obtained in vivo by 3T MRI and HR-pQCT. Materials and Methods: Postmenopausal osteopenic women (n = 52) were recruited for this study. HR-pQCT imaging of the radius and tibia was performed using the XtremeCT scanner, with a voxel size of 82 × 82 × 82 ,m3. MR imaging was performed on a 3T Signa scanner using SSFP imaging sequences, with a pixel size of 156 × 156 ,m2 and slice thickness of 500 ,m. Structure parameters were calculated using standard HR-pQCT and MRI analysis techniques. Relationships between measures derived from HR-pQCT, MRI, and DXA were studied. Results: Significant correlations between HR-pQCT and MRI parameters were found (p < 0.0001) and were strongest for Tb.N (r2 = 0.52), Ct.Th (r2 = 0.59), and site-specific Tb.Sp (r2 = 0.54,0.60). MRI and HR-pQCT provided statistically different values of structure parameters (p < 0.0001), with BV/TV and Tb.Th exhibiting the largest discrepancies (MR/HR-pQCT = 3,4). Although differences in the Tb.N values were statistically significant, the mean differences were on the order of our reproducibility measurements. Systematic differences between MRI and HR-pQCT analysis procedures leading to discrepancies in cortical thickness values were observed, with MRI values consistently higher. Minimal correlations were found between MRI or HR-pQCT parameters and DXA BMD or T-score, except between HR-pQCT measures at the radius and the ultradistal radius T-scores, where moderate correlations were found (r2 = 0.19,0.58). Conclusions: This study provides unique insight into two emerging noninvasive tools for bone structure evaluation. Our findings highlight the significant influence of analysis technique on results of in vivo assessment and underscore the importance of accounting for these differences when interpreting results from these modalities. [source] Sonographic evaluation of the sciatic nerve in patients with lower-limb amputationsMUSCLE AND NERVE, Issue 6 2010A. Salim Göktepe MD Abstract Hypertrophy of the sciatic nerve after lower-limb amputation in patients with sarcomas has been previously reported by magnetic resonance imaging; however, sonographic evaluation of the sciatic nerve after lower-limb amputation due to nonmalignant causes has not been done before. Therefore, the aim of this study was to perform imaging of the sciatic nerve in lower-limb amputees and to find out whether sonographic findings were related to clinical characteristics. Twenty-three males with lower-limb amputations due to traumatic injuries were enrolled. Sonographic evaluations were performed using a linear array probe (Aloka UST-5524-7.5 MHZ). Sciatic nerve diameters were measured bilaterally at the same level, and the values of the normal limbs were taken as controls. Sciatic nerve width and thickness values were found to be greater on the amputated sides than the normal sides (P = 0.001). The thickness values were greater in above-knee amputees than below-knee amputees (P = 0.05). Subjects with a neuroma also had thicker sciatic nerves (P = 0.04). The diameters were found not to change between subjects with different liners (P > 0.05), but they were correlated with time after amputation (r = 0.6, P = 0.006; r = 0.4, P = 0.05, respectively). Our results clearly show that the sciatic nerves were wider and thicker on the amputated sides. Amputation level, duration, and the presence of a neuroma seem to affect the eventual diameters of the nerves. Muscle Nerve, 2010 [source] Central corneal thickness in European (white) individuals, especially children and the elderly, and assessment of its possible importance in clinical measures of intra-ocular pressureOPHTHALMIC AND PHYSIOLOGICAL OPTICS, Issue 6 2002Michael J. Doughty Purpose:,To ascertain the impact of central corneal thickness (CCT, as assessed by pachometry) and central corneal curvature (as assessed by keratometry) on clinical measures of intra-ocular pressure (IOP, as assessed by tonometry), especially in the young and elderly. Methods:,Pachometry, keratometry and tonometry were carried out on three groups, namely children aged 5,15 years, adults aged 32,60 years, and elderly individuals aged between 61 and 82 years. For children, ultrasound pachometry was combined with non-contact tonometry (NCT), specular microscopy was used with Perkins tonometry in the adults, and ultrasound pachometry was used with Perkins tonometry for the elderly. Central corneal curvature was assessed by keratometry. Results:,The average CCT in children was 0.529 ± 0.034 mm (n=104, ±S.D.), averaged 0.533 ± 0.033 in adults (n=75) and 0.527 ± 0.034 mm (n=91) in the elderly. Tonometry values averaged 16.7 ± 2.9 mm in children, 13.0 ± 3.5 mmHg in adults and 13.6 ± 2.5 mm in the elderly group. Central corneal thickness values were not predictably different in relation to central corneal curvature values. Regression analyses indicated that the tonometry values were higher in both children and the elderly who had thicker corneas (and vice versa) (p , 0.003), with the measures increasing by 1.3 ± 0.4 and 2.6 ± 0.4 mmHg for a 10% difference in CCT in children and the elderly, respectively. For adults, no statistically significant difference in tonometry values could be demonstrated with respect to CCT (<1 mmHg for a 10% difference in CCT), and for no group were the CCT or tonometry values predictably different in relation to central corneal curvature values. Conclusions:,The results of these studies, albeit relatively small scale, indicate that in young or elderly individuals with essentially normal IOP and CCT measures, the tonometry values show only small differences with respect to CCT. The slope in the observed relationship was not that different from an average of 1.5 mmHg for a 10% different in CCT, as obtained from a literature analysis over a 30-year period. The magnitude of the effect does not provide evidence that pachometry needs to be routinely performed in glaucoma screening protocols based on tonometry. Notwithstanding, the finding of higher than expected tonometry values should be further investigated, by pachometry, especially in very young children and in the elderly. [source] Optimized-geometry ARROW waveguides using TiO2 as anti-resonant layerPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 3-4 2010Daniel O. Carvalho Abstract The simulation, fabrication and characterization of ARROW waveguides using dielectric films deposited by Plasma Enhanced Chemical Vapor Deposition (PECVD) and Sputtering techniques, are presented in this work. Amorphous titanium oxide (TiO2) films were used as first cladding layer and silicon oxynitride (SiOxNy) films, as core layer. Furthermore, homemade routines based in two computational methods were used, for numerical simulations: Transfer Matrix Method (TMM) for the determination of the optimum thickness values of the Fabry-Perot layers, and the Finite Difference Method (FDM) for 2D design and determination of the maximum width that allows single-mode operation. The utilization of thermally grown silicon oxide as second anti-resonant layer, along with improvements in the Reactive Ion Etching conditions for the definition of sidewalls of the optical waveguides were responsible for diminishing optical attenuations. Optimization of the waveguide rib height was done both through FDM simulations and experimentally. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Relationships between plasma leptin levels and body composition parameters measured by different methods in postmenopausal womenAMERICAN JOURNAL OF HUMAN BIOLOGY, Issue 5 2003Toivo Jürimäe The aim of this study was to determine the effects of body composition measured by different methods with different measurement errors on fasting plasma leptin level in normal body mass and obese postmenopausal women. It was hypothesized that the relationship between plasma leptin concentration and body fat is higher using more sophisticated laboratory methods (dual energy X-ray absorptiometry, DXA) in comparison with field methods (bioelectrical impedance analysis, BIA, or skinfold thickness) for body fat measurement because of the greater precision of DXA measurements. Thirty-five postmenopausal (55,83 years of age) healthy Estonian women were divided into two groups: BMI < 27kg/m2 as non obese (n = 18) and BMI> 27kg/m2 as obese (n = 17). Body composition was determined using DXA (total body, arms, legs, and trunk fat percent, fat mass, and LBM) and BIA methods. Body fat percent was significantly higher using the DXA method. Subcutaneous adipose tissue distribution was determined by measuring nine skinfold thicknesses. Body fat distribution was defined as the ratio of waist-to-hip (WHR) and waist-to-thigh (WTR) circumferences. Leptin was determined by means of radioimmunoassays. Leptin concentration was not significantly different between groups (19.0 ± 13.3 and 21.5 ± 21.5ng/ml in non obese and obese groups, respectively). Body fat percent and fat weight measured by DXA or BIA methods and all measured skinfold thickness values, except biceps and abdominal, were higher in obese women. Body height did not correlate significantly with leptin concentrations. The relationships between leptin concentration were highest with body weight (r = 0.67) and BMI (r = 0.73) values in the obese group. All measured body fat parameters using DXA or BIA methods correlated significantly with plasma leptin concentration in the obese group. LBM did not influence the leptin concentration in postmenopausal women. Stepwise multiple regression analysis indicated that the body fat percent measured using the DXA method was highly related to plasma leptin concentration in the obese group (63.2%; R2 × 100). When absolute fat mass parameters were considered, leptin concentration was related to the mass of arms fat tissue in the obese group of women (62.3%). Body fat percent measured by BIA was highly related to plasma leptin concentration in the obese group (63.3%). Only biceps skinfold thickness was related to leptin concentration (22.5% and 58.9%, in the nonobese and obese groups, respectively) from the nine measured skinfold thicknesses. WHR and WTR did not reflect leptin concentration in different groups of postmenopausal women. It was concluded that different methods of body composition estimation generate different correlations with plasma leptin concentration. Body fat percent and especially fat mass measured by DXA are the main predictors relating to plasma leptin concentration in obese, but not in nonobese, postmenopausal women. In addition, fat mass in arms measured by DXA and biceps skinfold thickness were also highly related to leptin concentration. Am. J. Hum. Biol. 15:628,636, 2003. © 2003 Wiley-Liss, Inc. [source] Machine learning classifiers for glaucoma diagnosis based on classification of retinal nerve fibre layer thickness parameters measured by Stratus OCTACTA OPHTHALMOLOGICA, Issue 1 2010Dimitrios Bizios Abstract. Purpose:, To compare the performance of two machine learning classifiers (MLCs), artificial neural networks (ANNs) and support vector machines (SVMs), with input based on retinal nerve fibre layer thickness (RNFLT) measurements by optical coherence tomography (OCT), on the diagnosis of glaucoma, and to assess the effects of different input parameters. Methods:, We analysed Stratus OCT data from 90 healthy persons and 62 glaucoma patients. Performance of MLCs was compared using conventional OCT RNFLT parameters plus novel parameters such as minimum RNFLT values, 10th and 90th percentiles of measured RNFLT, and transformations of A-scan measurements. For each input parameter and MLC, the area under the receiver operating characteristic curve (AROC) was calculated. Results:, There were no statistically significant differences between ANNs and SVMs. The best AROCs for both ANN (0.982, 95%CI: 0.966,0.999) and SVM (0.989, 95% CI: 0.979,1.0) were based on input of transformed A-scan measurements. Our SVM trained on this input performed better than ANNs or SVMs trained on any of the single RNFLT parameters (p , 0.038). The performance of ANNs and SVMs trained on minimum thickness values and the 10th and 90th percentiles were at least as good as ANNs and SVMs with input based on the conventional RNFLT parameters. Conclusion:, No differences between ANN and SVM were observed in this study. Both MLCs performed very well, with similar diagnostic performance. Input parameters have a larger impact on diagnostic performance than the type of machine classifier. Our results suggest that parameters based on transformed A-scan thickness measurements of the RNFL processed by machine classifiers can improve OCT-based glaucoma diagnosis. [source] Repeatability in and interchangeability between the macular and the fast macular thickness map protocols: a study on normal eyes with Stratus optical coherence tomographyACTA OPHTHALMOLOGICA, Issue 7 2009Urban Eriksson Abstract. Purpose:, To collect a normal material and to compare the macular and the fast macular thickness map protocols regarding normal values and repeatability. Methods:, Sixty-seven individuals underwent three repeated scans with the macular thickness protocol; 45 of them also had three scans with the fast thickness protocol in Stratus optical coherence tomography (OCT). The maps were divided into nine ETDRS fields, where thickness values were presented. The repeatability was calculated as intraclass correlation coefficient (ICC), coefficient of variance (CV) and coefficient of repeatability (CR). For comparison between the two protocols, limits of agreement were determined according to Bland,Altman. Results:, Normal values for the two protocols were very close. Repeatability was high. ICC for all areas was 0.92,0.98. CV was less than 1% and CR was 6,8 ,m for both protocols, with the exception of the fovea in the fast protocol (where CV was 1.44% and CR 12.4 ,m). Limits of agreement between the two protocols were less than 10 ,m as a rule. Conclusion:, Normal values for the protocols are equal and they both have excellent repeatability. The fast macular map is a good alternative with the possible exception of the fovea, where variation is twice that of the macular thickness map. [source] A population-based study of macular thickness in full-term children assessed with Stratus OCT: normative data and repeatabilityACTA OPHTHALMOLOGICA, Issue 7 2009Urban Eriksson Abstract. Purpose:, We aimed to determine normal macular thickness values, assessed with optical coherence tomography (OCT), in a population of full-term children of normal birthweight. Methods:, A total of 56 children, aged 5,16 years, randomly chosen from the population register, were examined with Stratus OCT. Only children with visual acuity < 0.2 logMAR, spherical equivalent of , 3 to + 3 D and astigmatism < 2 D were included. The fast macular map protocol was used and three examinations were performed in each eye. One eye was then randomized for further analyses. Mean values for the nine ETDRS areas, foveal minimum thickness and macular volume were calculated for 55 eyes. Coefficients of variance and intraclass correlations were calculated for each area. Results:, All children co-operated well and no child was excluded for lack of concentration. Mean ± standard deviation central macular thickness was 204 ± 19 ,m. Mean total macular volume was 7.11 ± 0.35 mm3. No correlations were found between age, gender and macular thickness. Coefficients of variance were < 2% and intraclass correlations were > 0.9 in all areas, except the foveal minimum. Conclusions:, Normal values for macular thickness in healthy full-term children were reported. As the Stratus OCT provides normal values only for adults, these data are a better alternative for comparison with children with retinal abnormalities. We concluded that OCT is suitable for examining the retina in children aged 5,16 years and has the same high level of repeatability as in adults. [source] RTVue Fourier-domain OCT: reproducibility of RNFLT and macular thickness measurementsACTA OPHTHALMOLOGICA, Issue 2009A GARAS Purpose To evaluate the reproducibility of peripapillary retinal nerve fiber layer thickness (RNFLT) and macular thickness (MT) measurements with the RTVue-100 Fourier-domain optical coherence tomography, and to determine the influence of pupil dilation, patients' experience in examinations and severity of glaucoma. Methods One eye of 14 normal subjects, 11 patients with moderate, 12 patients with severe glaucoma and 40 screening trial participants were imaged 5 times on the same day. For the hospital-based patients, the measurement series was repeated after pupil dilation and 3 months later. Results For the RNFLT and the MT parameters, intrasession intraclass correlation coefficient (ICC) varied between 93.9 and 99.0%, intrasession coefficient of variation (CV) between 1.95 and 5.69 %, and intratest variability between 3.11 and 9.13 µm. Most thickness values, all intrasession CV and intratest variability values and the signal strength index remained unchanged after pupil dilation. Most intrasession CV values increased significantly with increasing disease severity. Patients' experience in imaging examinations had no influence on intrasession CV. Intratest variability and intrasession CV represented 79.1 to 98.6 % and 77.1 to 95.0 % of test-retest variability and intervisit CV, respectively. Conclusion Reproducibility of RNFLT and MT measurement with the RTVue-100 OCT are satisfactory for clinical purposes both in normals and glaucoma patients. Pupil dilation and patients' experience in imaging examinations do not influence the reproducibility of the measurements clinically significantly. Commercial interest [source] Viscoanaesthesia in cataract surgery: a prospective, randomized clinical trialACTA OPHTHALMOLOGICA, Issue 4 2009Juha Välimäki Abstract. Purpose:, We aimed to compare viscoanaesthesia (VisThesia) with intracameral lidocaine in cataract surgery carried out under topical anaesthesia. Methods:, In this prospective study 98 patients were randomly assigned to receive VisThesia (group 1, n = 49) or 0.5 cc of 1% unpreserved lidocaine (group 2, n = 49). All surgery was carried out by one surgeon using clear corneal technique. Pachymetry, the status of the cornea and anterior chamber, and intraocular pressure (IOP) were checked pre- and postoperatively. Results:, Mean pain scores were 0.12 (maximum: 3) in group 1 and 0.37 in group 2; the difference between the groups was not statistically significant (95% confidence interval [CI] 0.003,0.487; p = 0.05). A total of 48 patients in group 1 (98%) and 49 in group 2 (100%) reported no discomfort or only mild discomfort. No significant differences in flare and cells in the anterior chamber or IOP were found between the two study groups. There was a significantly greater frequency of corneal oedema in group 1 (p = 0.001). Postoperative central corneal thickness values were also significantly higher in group 1 (95% CI 11.64,57.24; p = 0.003). Conclusions:, Results suggest that viscoanaesthesia provides a level of comfort during cataract surgery under topical anaesthesia similar to that facilitated by intracameral lidocaine. However, patients who are given viscoanaesthesia may have increased risk for postoperative corneal oedema. [source] | ||||||||||