Home About us Contact
|
Home About us Contact | ||
|
|
||
Thickness Measurements (thickness + measurement)
Selected AbstractsComparison of two partial coherence interferometers for corneal pachymetry in high myopia and after LASIKACTA OPHTHALMOLOGICA, Issue 4 2009Anders Ivarsen Abstract. Purpose:, We aimed to compare the Haag-Streit optical low-coherence reflectometry (OLCR) pachymeter and the Zeiss Anterior Chamber Master (ACMaster) for measuring central corneal thickness (CCT) in high myopes and after laser in situ keratomileusis (LASIK) for myopia. Methods:, Central corneal thickness was measured in 55 eyes of 30 myopic subjects (spherical equivalent refraction of , 5.25 D to , 10.75 D, maximal astigmatism of , 2 D), and in 37 eyes of 21 patients 3 months after LASIK for myopia (preoperative spherical equivalent refraction of , 6.0 D to , 10.75 D, maximal astigmatism of , 2 D). All measurements were performed with the Haag-Streit OLCR pachymeter and the Zeiss ACMaster, using group refractive indices of 1.376 and 1.3851, respectively. Thickness measurements were compared using paired t -tests, Pearson's correlation, linear regression and Bland,Altman plots. Results:, In myopic subjects, CCT measured 531 ± 28 ,m and 533 ± 27 ,m with the OLCR pachymeter and the ACMaster, respectively (p < 0.01); all measurements correlated closely (r = 0.99, p < 0.01). In LASIK-treated eyes, CCT measured 472 ± 24 ,m using the OLCR pachymeter and 475 ± 23 ,m using the ACMaster (p < 0.01), again with close correlation between the two instruments (r = 0.99, p < 0.01). Conclusions:, Measurements of CCT in high myopes and after myopic LASIK were very similar with the Haag-Streit OLCR pachymeter and the Zeiss ACMaster. Using the current group refractive indices, the observed difference between the two instruments of < 3 ,m is of little clinical importance. Thus, it would seem safe to use the OLCR pachymeter and the ACMaster interchangeably for CCT measurements in myopia as well as after myopic LASIK. [source] A Noncontact Ultrasound Approach for Mechanical Property Determination of CheesesJOURNAL OF FOOD SCIENCE, Issue 7 2003B.-K. Cho ABSTRACT: Noncontact ultrasound parameters, such as velocity and attenuation coefficient, were directly measured using air instability compensation transducers and correlated with Young's modulus, hardness, and toughness of different types of cheeses. Ultrasound velocity was highly correlated with the mechanical properties of cheeses whereas no significant relationship between the ultrasound energy attenuation coefficient and the mechanical properties were shown. The noncontact ultrasound technique demonstrated excellent performance for thickness measurement of cheeses with an accuracy of 99.98% (standard error = 0.089 mm). Results indicated that noncontact air instability compensation ultrasound technique has a good potential for nondestructive and accurate measurement of ultrasound parameters, thickness, and mechanical properties of food materials. [source] High-pressure short time behavior of traction fluidsLUBRICATION SCIENCE, Issue 1 2006Nobuyoshi Ohno Abstract The squeeze film formation ability of traction fluids is studied under impact load by dropping a steel ball-bearing against a flat anvil made of mild steel. The effect of the pressure,viscosity coefficient and of the viscosity is investigated for plastic impact. The depth difference between the lubricated surface dent and the dry dent increases linearly with the product ,, of the pressure,viscosity coefficient , and the viscosity ,. The importance of the lubricant parameter ,, is observed under the squeeze film formation ability from contact voltage or elastohydrodynamic lubrication central film thickness measurement at rolling condition. The intensity of each impact collision is measured by means of an acoustic emission (AE) sensor. The high-pressure short-time solidification of traction fluids was confirmed by dent analysis after the impact tests and AE analysis under impact loads. Copyright © 2006 John Wiley & Sons, Ltd. [source] Investigation on steam oxidation behaviour of TP347H FG Part 1: Exposure at 256 barMATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 7 2005J. Jianmin Abstract The stainless steel TP347H FG is a candidate material for the final stage tubing of superheater and reheater sections of ultra supercritical boilers operated at steam temperatures up to 620°C in the mild corrosion environments of coal-firing. A series of field tests has been conducted with the aforementioned steel in coal-fired boilers and this paper focuses on the steam oxidation behaviour for specimens tested at various metal temperatures for exposure times of 7700, 23000 and 30000 hours as investigated by light optical and scanning electron microscopy. The oxide present on the specimens is a duplex oxide, where the outer layer consists of two sub-layers, an iron oxide layer and an iron-nickel oxide layer; the inner layer is chromium rich chromium-iron-nickel oxide. Microstructure examination showed that for all these samples the varying grain size of subsurface metal affected the oxide thickness, where the larger the metal grain size, the thicker the oxidation scale. This gave the appearance of uneven inner oxides with a varying pit thickness. Comparison of the pit thickness measurement and oxide composition reveals that the oxidation rate is fast during the initial oxidation stage, but the subsequent growth of oxide from further exposure is slower due to the formation of a healing layer consisting of chromium rich oxide near original alloy grain boundaries. At a temperature region above 600°C a thin oxide rich in chromium and manganese is sometimes formed. In addition precipitation of secondary carbides in the bulk metal also occurs at this temperature region. [source] The role of optical coherence tomography in the detection of pituitary adenomaACTA OPHTHALMOLOGICA, Issue 7 2009Charlotta Johansson Abstract. Purpose:, To analyse retinal nerve fibre layer (RNFL) thickness in eyes with compression of the optic chiasm by a pituitary adenoma. RNFL thickness was analysed with optical coherence tomography (OCT) and compared to visual field measurements using high-pass resolution perimetry (HRP). Methods:, Sixteen eyes from eight patients with pituitary adenoma were studied. All had bitemporal visual field depression caused by compression of the optic chiasm. Patients were submitted to an ophthalmic examination more than 14 months after surgery (seven patients had undergone trans-sphenoidal and one trans-cranial adenomectomy). The examination included HRP, fundus photography and measurement of the peripapillar RNFL thickness using OCT. Results:, In spite of temporal visual field depression, not all eyes showed reduced RNFL thickness by OCT. This was also true for some eyes in which RNFL was judged to be reduced on fundus photographs. Contrary to our expectations, RNFL thickness in the nasal quadrant was normal in nine of the 16 eyes. Corresponding figures for the superior, inferior and temporal quadrants were eight, six and five, respectively. The overall RNFL thickness, as measured by OCT, did not correlate well with neural capacity, which is an index of remaining retino-cortical neural channels in HRP. Conclusion:, RNFL thickness as measured with OCT was reduced in most, but not all, eyes with temporal field depression caused by chiasmal compression. The pattern of RNFL loss did not correlate well with the visual field defect. Sensitivity of RNFL thickness measurement in OCT was low. The method has limited value in the diagnosis of pituitary tumour compression. [source] Retinal nerve fiber layer thickness and central corneal thickness in ocular hypertensive patients and healthy subjectsACTA OPHTHALMOLOGICA, Issue 2009AM BRON Purpose To establish the correlation between central corneal thickness (CCT) and retinal nerve fiber layer (RNFL) thickness in ocular hypertensive patients and healthy subjects. Methods We prospectively collected charts of healthy subjects and ocular hypertensive (OHT) patients in one academic center between 2007 and 2008. OHT patients were defined by two measurements of intraocular pressure superior to 21mmHg without treatment, open angle in gonioscopy, normal appearing optic nerve head and normal visual field test Standard Automated Perimetry (SAP SITA) and Frequency Doubling Technique (FDT). Every patient underwent a standard clinical examination including optic nerve head examination, intraocular pressure, CCT measurement by ultrasonic (US) and anterior segment OCT pachymetry, visual field testing (SAP and FDT), RNFL thickness by scanning laser polarimetry (GDX-VCC) and optical coherence tomography (OCT). Results Eighty healthy subjects and 60 OHT patients were included. A correlation between US CCT and OCT CCT was found in both groups (r2=0.85 and r2= 0.87, p<0.001). There was no significant difference (p>0.15) in GDX-VCC and OCT RNFL thickness in both groups. In controls there was no correlation of any RNFL thickness measurement with the CCT. In OHT patients, the US CCT was weakly correlated with the average TSNIT evaluated by GDX-VCC (r2= 0.04, p<0.02). Conclusion This study did not show any relevant correlation between the RNFL thickness evaluated by GDX-VCC and the US CCT in healthy individuals and in OHT patients with a normal FDT. [source] Involvement of the thalamocortical network in TLE with and without mesiotemporal sclerosisEPILEPSIA, Issue 8 2010Susanne G. Mueller Summary Purpose:, The thalamus plays an important role in seizure propagation in temporal lobe epilepsy (TLE). This study investigated how structural abnormalities in the focus, ipsilateral thalamus and extrafocal cortical structures relate to each other in TLE with mesiotemporal sclerosis (TLE-MTS) and without hippocampal sclerosis (TLE-no). Methods:, T1 and high-resolution T2 images were acquired on a 4T magnet in 29 controls, 15 TLE-MTS cases, and 14 TLE-no. Thalamus volumes were obtained by warping a labeled atlas onto each subject's brain. Deformation-based morphometry was used to identify regions of thalamic volume loss and FreeSurfer for cortical thickness measurements. CA1 volumes were obtained from high-resolution T2 images. Multiple regression analysis and correlation analyses for voxel- and vertex-based analyses were performed in SPM2 and FreeSurfer. Results:, TLE-MTS had bilateral volume loss in the anterior thalamus, which was correlated with CA1 volume and cortical thinning in the mesiotemporal lobe. TLE-no had less severe volume loss in the dorsal lateral nucleus, which was correlated with thinning in the mesiotemporal region but not with extratemporal thinning. Discussion:, The findings suggest that seizure propagation from the presumed epileptogenic focus or regions close to it into the thalamus occurs in TLE-MTS and TLE-no and results in circumscribed neuronal loss in the thalamus. However, seizure spread beyond the thalamus seems not to be responsible for the extensive extratemporal cortical abnormalities in TLE. [source] Physical indicators of cartilage health: the relevance of compliance, thickness, swelling and fibrillar textureJOURNAL OF ANATOMY, Issue 6 2003Neil D. Broom Abstract This study uses a bovine patella model to compare the relative merits of on-bone compliance and thickness measurements, free-swelling behaviour, and structural imaging with differential interference contrast (DIC) light microscopy to assess the biomechanical normality of the cartilage matrix. The results demonstrate that across a spectrum of cartilage tissues from immature, mature, through to mildly degenerate, and all with intact articular surfaces, there is a consistent pattern of increased free swelling of the isolated general matrix with age and degeneration. High swelling was always associated with major structural alterations of the general matrix that were readily imaged using DIC light microscopy. Conversely, for all tissue groups, no relationship was observed between thickness vs. compliance and compliance vs. general matrix swelling. Only in the proximal aspects of the normal mature and degenerate tissues was there a correlation between thickness and general matrix swelling. Free-swelling measurements combined with fibrillar texture imaging using DIC light microscopy are therefore recommended as providing a reliable and quick method of assessing the biomechanical condition of the cartilage general matrix. [source] Prediction of oxygen transmission rate for thermoformed traysPACKAGING TECHNOLOGY AND SCIENCE, Issue 6 2004Marit KvalvĹg Pettersen Abstract There is a desire in the food industry to be able to estimate the oxygen transmission rate (OTR) of packages by knowing the permeability data of unconverted sheet/film, instead of measuring the OTR of packages. Due to thermoforming, the permeability of a material changes and therefore it is difficult to estimate the permeability (OTR) of converted trays from the OTR values of unconverted material. This paper evaluates the possibilities and limitations of predicting the OTR of thermoformed trays. Different methods for the calculation of OTR due to thickness measurements were compared. The use of theoretical thickness was satisfactory in the calculation of OTR of trays based on the OTR of unconverted sheet, area and thickness. Both linear and quadratic regression models were evaluated. Validation of the regression models was made by comparing the measured and calculated OTR of trays made of PS/EVOH/PE, A-PET/PE, PS/PE and PP/PE. These trays were manufactured on different thermoforming machines, different processing parameters and different sizes of mould. None of the models (linear and quadratic) were suitable for the calculation of OTR of trays made of PS/PE and PP/PE. Both linear and quadratic models gave satisfactory agreement with measured values for trays made of both PS/EVOH/PE and A-PET/PE. This case study indicates that a general equation for the calculation of OTR for different polymer combinations was not possible to generate. The equations presented in this paper are strictly applicable only for the polymer combinations used in this experiment, and can not be considered as general equations. Copyright © 2004 John Wiley & Sons, Ltd. [source] Population screening for fetal trisomy 21: easy access to screening should be balanced against a uniform ultrasound protocolPRENATAL DIAGNOSIS, Issue 11 2005Wilfried J. A. Gyselaers Abstract Objectives To evaluate the performance of a first-trimester fetal aneuploidy screening program, with a documented underestimation of nuchal translucency thickness measurements (NT) compared to the Fetal Medicine Foundation (FMF) reference range. Methods We analysed the data of Algemeen Medisch Laboratorium (AML) in Antwerp, Belgium, on combined screening with pregnancy-associated plasma protein-A (PAPP-A), free ,-human chorionic gonadotropin (FB-hCG) and NT. NT-multiples of the median (MoM), relative to the FMF reference range, were used for risk calculations. Results The proportion of first-trimester screening tests in the total of serum screening tests increased from 1.3% (125/9424) in 2000 to 53.1% (6577/12 377) in 2003. Only 11.4% (1514/13 267) of NT measurements were performed according to FMF criteria. The 80.8% (21/26) trisomy 21 (T21) detection rate (DR) at cut off 1:300 resulted from maternal serum screening. NT measurements did not add to this DR, but reduced the false-positive rate from 16.8% (2212/13181) to 8.6% (1130/13181). Only 23.8% (5/21) of T21 detections were by FMF trainees. Conclusion Easy access to screening and maternal serum parameters accounted for the majority of T21 detections in our first-trimester combined screening program. Copyright © 2005 John Wiley & Sons, Ltd. [source] Contributions of Mouse Genetic Background and Age on Anterior Lens Capsule ThicknessTHE ANATOMICAL RECORD : ADVANCES IN INTEGRATIVE ANATOMY AND EVOLUTIONARY BIOLOGY, Issue 12 2008Brian P. Danysh Abstract Accurate lens capsule thickness measurements are necessary for studies investigating mechanical characteristics of the capsule. Confocal Z -axis imaging was used to measure the anterior lens capsule thickness of living intact lenses with minimal tissue manipulation. Measurements of the anterior capsule thickness is reported for the first time in young and old mice from four inbred strains, BALB/c, FVB/N, C57BL/6, and 129X1, and the outbred strain ICR. Our data demonstrates that the mouse anterior lens capsule continues to grow postnatally similar to that described in other mammals. It is also shown there is a significant difference in anterior lens capsule thickness between unrelated mouse strains, suggesting that capsule thickness is a quantitative trait shared by strains with common ancestry. Measurements, taken from other regions of FVB/N capsules revealed the anterior pole to be the thickest, followed by the equatorial region and posterior pole. In addition to mouse, anterior capsule measurements taken from intact cattle, rabbit, rat lenses, and human capsulotomy specimens correlated with the overall size of the animal. Anat Rec, 2008. © 2008 Wiley-Liss, Inc. [source] Combined intravitreal anti-vascular endothelial growth factor (Avastin®) and photodynamic therapy to treat retinal juxtapapillary capillary haemangiomaACTA OPHTHALMOLOGICA, Issue 5 2010Stefan Mennel Abstract. Objective:, Retinal capillary haemangioma complications are characterized by progressive exudation with consecutive intraretinal and subretinal leakage. A successful therapy without side-effects has not been found. We report a case of retinal juxtapapillary capillary haemangioma causing consecutive leakage with macular involvement. The tumour was treated with a combination of anti-vascular endothelial growth factor (VEGF) and photodynamic therapy (PDT) and was followed for 1 year. Methods:, A 44-year-old woman with retinal juxtapapillary capillary haemangioma in the right eye experienced a decrease of visual acuity from 20/20 to 20/60 because of a severe leakage from the tumour involving the macula with lipid depositions. Two sessions of PDT (sparing the part of the haemangioma located within the optic disc) and five injections of bevacizumab were applied in a period of 5 months. Visual acuity, visual field testing, retinal thickness measurements, fundus photography and fluorescein angiography were performed to evaluate the treatment effect. Results:, One year after the last injection, visual acuity increased to 20/40. All lipid exudates at the posterior pole resolved. Retinal thickness decreased from 490 to 150 ,m with the restoration of normal central macular architecture. Leakage in fluorescence angiography reduced significantly, but hyperfluorescence of the tumour was still evident. Visual field testing and angiography did not show any treatment-related vaso-occlusive side-effects. Conclusion:, In this single case, the combination of anti-VEGF and PDT appeared to be an effective strategy for the treatment of retinal juxtapapillary capillary haemangioma without side-effects. Further studies with a greater number of eyes and adequate follow-up are necessary to support these first clinical results. [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] 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] An evaluation of the retinal nerve fiber layer thickness by scanning laser polarimetry in individuals with dementia of the Alzheimer typeACTA OPHTHALMOLOGICA, Issue 2 2001Hélčne Kergoat ABSTRACT. Purpose: To determine, using scanning laser polarimetry, whether or not the retinal nerve fiber layer (RNFL) is altered in dementia of the Alzheimer type (DAT). Methods: Thirty individuals with mild to moderate DAT and 30 healthy age-matched controls participated in the study. Fundus images were acquired with a Nerve Fiber Analyzer. RNFL thickness measurements were obtained under an ellipse located 1.75 disc diameter from the optic nerve head (ONH) center. Results: No differences in RNFL thickness were observed between DAT and healthy subjects. The regional distribution of RNFL thickness was similar between the two test groups, with the RNFL being thickest in the superior and inferior retinal segments relative to the nasal and temporal regions. Conclusions: Our data indicate that the RNFL is not altered in DAT, at least in the earlier stages of the disease. [source] Deep fascia on the dorsum of the ankle and foot: Extensor retinacula revisitedCLINICAL ANATOMY, Issue 2 2007Marwan F. Abu-Hijleh Abstract This study revisits the anatomy of the deep fascia over the distal leg, ankle, and dorsum of the foot. The arrangement of the deep fascia in these regions was recorded in 14 lower limbs of adult cadavers using photographs and drawings. The fascial layer from all three sites was subsequently removed in toto, and serial thickness measurements were made along its entire length. In addition, fiber disposition was studied under polarized light, and sections were stained to demonstrate collagen. The arrangement of deep fascia is complex. A common and novel finding at all levels is a crisscross, lattice-like arrangement of fibers. There was little evidence of the clearly defined sturdy band of the superior extensor retinaculum (SER) or of the Y-shaped inferior retinaculum (IER) commonly illustrated in topographical anatomy texts. The SER is a complex area with several thickenings commencing about 3 cm proximal to the tip of the lateral malleolus and gradually increasing to reach a maximum of 270 ,m about 5 cm above the malleolus, then gradually returning to original thickness, about 9 cm above the malleolus. Fibers crossing diagonally to each other are a feature of the region. The IER characteristically has two forms: either a cross-shaped band (9 specimens) or a thickened "node" with small extensions radiating toward the malleoli (5 specimens), located about 1,2 cm distal to the lateral malleolus and centred over the common tendon of extensor digitorum where it has maximum thickness (430 ,m). The deep fascia is thickened and firmly attached over both malleoli and to the tarsals and metatarsals along both borders of the foot. In general, the deep fascial structures were thicker in males than those in females. Clin. Anat. 20:186,195, 2007. © 2006 Wiley-Liss, Inc. [source] | ||||||||||||||||