Error In Thickness Measurement Research Articles

Development of a Musculoskeletal Ultrasound Protocol to Examine Upper Extremity Rehabilitation Outcomes in Systemic Sclerosis.

This study developed a musculoskeletal ultrasound (MSUS) protocol to evaluate rehabilitation outcomes in systemic sclerosis. Three MSUS methods (grey scale, Doppler, strain elastography) and two acquisition techniques (long versus short axis; transducer on skin versus floating on gel) were examined in the forearm before and after rehabilitation treatment. For grey-scale, tissue thickness measures, intra- and inter-rater reliability were calculated (ICCs), and paired t-tests examined differences among techniques. Five people with diffuse cutaneous systemic sclerosis participated. The most valid and reliable grey-scale technique was with the transducer in long-axis, floating on gel. Doppler and strain elastography did not detect changes. Both dermal and subcutaneous thickness measurement error was small; intra- and inter-rater reliability was good to excellent. Preliminary data indicate that treatment may lead to dermal thinning. A replicable protocol was established and may be an adjunct to rehabilitation outcome measurement in systemic sclerosis.

Measurement and Error Analysis of Cu Film Thickness With Ta Barrier Layer on Wafer for CMP Application

Accurate thickness measurement of copper (Cu) film on silicon (Si)-based wafers is very important in the chemical mechanical polishing (CMP) process. For thickness measurement of Cu film, the eddy current method is widely adopted due to noncontact, high-efficiency, and high-accuracy characteristics. However, existing thickness measurements of Cu film ignore the effect of tantalum (Ta) barrier layer between Cu film and Si substrate, which makes the measurement result inaccurate. Therefore, it is necessary to investigate the effect of Ta barrier layer on thickness measurement of Cu film. In this article, an improved eddy current sensor system with a nanoscale resolution is proposed. It is based on the inductance–capacitance resonance principle and theoretical analysis is conducted. Several Si-based specimens with pure Cu film, pure Ta film, and Cu–Ta multilayer structure are prepared and measured. Experimental results show that there exists a balance thickness of Ta barrier layer as a threshold in Cu–Ta multilayer structure. When the thickness of Ta barrier layer is larger than the threshold, the measured thickness of Cu film increases with the increase of Ta barrier layer thickness. Conversely, the measured thickness of Cu film decreases when Ta barrier layer is thinner than the threshold. Then, a compensation method is presented, and the error of thickness measurement of Cu film is reduced to less than 6 nm.

Semi-automated registration and segmentation for gingival tissue volume measurement on 3D OCT images.

The change in gingival tissue volume may be used to indicate changes in gingival inflammation, which may be useful for the clinical assessment of gingival health. Properly quantifying gingival tissue volume requires a robust technique for accurate registration and segmentation of longitudinally captured 3-dimensional (3D) images. In this paper, a semi-automated registration and segmentation method for micrometer resolution measurement of gingival-tissue volume is proposed for 3D optical coherence tomography (OCT) imaging. For quantification, relative changes in gingiva tissue volume are measured based on changes in the gingiva surface height using the tooth surface as a reference. This report conducted repeatability tests on this method drawn from repeated scans in one patient, indicating an error of the point cloud registration method for oral OCT imaging is 63.08 ± 4.52µm (1σ), and the measurement error of the gingival tissue average thickness is -3.40 ± 21.85µm (1σ).

Development of wall-thinning evaluation procedure for nuclear power plant piping - Part 2: Local wall-thinning estimation method

Flow-accelerated corrosion (FAC), liquid droplet impingement erosion (LDIE), cavitation and flashing can cause continuous wall-thinning in nuclear secondary pipes. In order to prevent pipe rupture events resulting from the wall-thinning, most NPPs (nuclear power plants) implement their management programs, which include periodic thickness inspection using UT (ultrasonic test). Meanwhile, it is well known in field experiences that the thickness measurement errors (or deviations) are often comparable with the amount of thickness reduction. Because of these errors, it is difficult to estimate wall-thinning exactly whether the significant thinning has occurred in the inspected components or not. In the previous study, the authors presented an approximate estimation procedure as the first step for thickness measurement deviations at each inspected component and the statistical & quantitative characteristics of the measurement deviations using plant experience data. In this study, statistical significance was quantified for the current methods used for wall-thinning determination. Also, the authors proposed new estimation procedures for determining local wall-thinning to overcome the weakness of the current methods, in which the proposed procedure is based on analysis of variance (ANOVA) method using sub-grouping of measured thinning values at all measurement grids. The new procedures were also quantified for their statistical significance. As the results, it is confirmed that the new methods have better estimation confidence than the methods having used until now.

Dynamic modulation performance of ferroelectric liquid crystal polarization rotators and Mueller matrix polarimeter optimization

A ferroelectric liquid crystal polarization rotator (FLCPR) has been widely used in polarization measurement due to its fast and stable modulation characteristics. The accurate characterization of the modulation performance of FLCPR directly affects the measurement accuracy of the instrument based on liquid crystal modulation. In this study, FLCPR is accurately characterized using a self-developed high-speed Stokes polarimeter. Strong linear and weak circular birefringence are observed during modulation processes, and all the optical parameters of FLCPR are dependent on driving voltage. A dual FLCPR-based Mueller matrix polarimeter is designed on the basis of the Stokes polarimeter. The designed polarimeter combines the advantages of the high modulation frequency of FLCPR and the ultrahigh temporal resolution of the fast polarization measurement system in the Stokes polarimeter. The optimal configuration of the designed polarizer is predicted in accordance with singular value decomposition. A simulated thickness measurement of a 24 nm standard SiO2 thin film is performed using the optimal configuration. Results show that the relative error in thickness measurement caused by using the unsatisfactory modulation characteristics of FLCPR reaches up to −4.34%. This finding demonstrates the importance of the accurate characterization of FLCPR in developing a Mueller matrix polarizer.

Methodology of dry and wet compressibility measurement

This paper describes a methodology to obtain and analyse data in composite reinforcement fabric compaction tests in dry and saturated conditions using a standard electromechanical test machine and an indirect thickness measurement method.The main goal is the identification of machine compliance sources and the understanding of its effects in typical compression tests and compression with relaxation stage tests. This methodology was used in the first international compressibility benchmark exercise promoted by NPL (National Physics Laboratory, UK) in the years 2017 and 2018. The methodology accounts for the test setup compliance and evaluates errors in fabric thickness measurements in the range of tens of microns especially during the relaxation phase. Overall, the setup compliance and data analysis strategy proved to have a significant effect on the data if not properly accounted for.

The Mathematical Model of the Broadband Transmission X-Ray Thickness Gauge

The mathematical model of the broadband transmission X-ray thickness gauge is developed. The mathematical model consists of sectors: generation and transformation of radiometric signals; equation of transmission X-ray thickness gauge; error estimation of thickness measurement; performance rating. The example of the use of the proposed model to calculate of the transmission X-ray thickness gauge for aluminum items is provided. In the example the dependences of integral mass X-ray attenuation coefficients and the thickness of monitored objects made from aluminum are calculated. The range of optimum measured thickness depending on the maximum X-ray energy was selected, the measurement time to provide the desired thickness measurement error was estimated. The possibility of measuring the thickness of a cooper test object for a wide beam conditions has been experimentally confirmed.

Structured planar laser-induced fluorescence (S-PLIF) for the accurate identification of interfaces in multiphase flows

Annular flows are employed in numerous engineering and industrial processes relating to the chemical, oil and gas, solar and nuclear energy industries. Yet, the reliable and detailed (i.e., time- and space-resolved) measurement of film thickness in these flows continues to elude us, as the moving and wavy interface renders the application of optical diagnostics, such as planar laser-induced fluorescence (PLIF), particularly challenging. In this research article, we present a novel adaptation of PLIF, which we refer to as structured PLIF (S-PLIF), which can suppress the errors in PLIF-derived film thickness measurements that arise due to total internal reflection (TIR) of the emitted fluorescence at the phase boundary. The proposed measurement approach relies on the periodic modulation of the laser-light intensity and angled illumination of the examined region of the flow, in order to generate fluorescence images with alternating bright and dark regions at an angle to the channel wall and film interface. An image-processing methodology capable of recovering the location of the true gas-liquid interface from such images is presented, and the application of S-PLIF is demonstrated in liquid films in a vertical pipe over the Reynolds number range ReL≈150−1500. The results from this technique are compared to simultaneously recovered, “conventional” (uncorrected) PLIF data, as well as data from other techniques over the same range of conditions, demonstrating the efficacy of S-PLIF. A comparison amongst S-PLIF data obtained with the observation angle between the laser-sheet plane and the camera’s observation axis set to β=70∘ and 90 ∘ is also performed, showing that the employment of β=70∘ is highly advantageous in avoiding distortions caused by optical interactions of the emitted fluorescence at the free surface of circumferentially non-uniform films. The instantaneous and average film-thickness uncertainties of S-PLIF are estimated to be below 10% and 5%, respectively, when measuring smooth films; an improvement over the other optical measurement techniques considered in this work. Finally, the application of S-PLIF is demonstrated in the presence of a gas-shear flow with gas entrainment in the liquid, and simultaneously with particle image velocimetry (PIV).

Optical Coherence Tomography Segmentation Errors of the Retinal Nerve Fiber Layer Persist Over Time.

To identify whether optical coherence tomography (OCT) segmentation errors in RNFL thickness measurements persist longitudinally. This was a cohort study. We used spectral domain OCT (Spectralis) to measure RNFL thickness in a 6-degree peripapillary circle, and exported the native "automated segmentation only" results. In addition, we exported RNFL thickness results after "manual refinement" to correct errors in the automated segmentation, and used the differences in these measurements as "error" in segmentation. We used Bland-Altman plots and linear regression to determine the magnitude, location, and repeatability of RNFL thickness error in all twelve 30-degree sectors and compared the error at baseline to follow-up time points at 6 months, 2 years, 3 years, and 4 years. We included 406 eyes from 213 participants. The 95% confidence interval for errors at baseline was -6.5 to +13.2 μm. The correlation between the baseline error and the errors in the follow-up time periods were high (r>0.5, P<0.001 for all). Automated segmentation had a smaller SD of residuals from the longitudinal trend line when compared to manual refinement (1.56 vs. 1.80 μm, P<0.001), and a higher ability (P=0.009) to monitor progression using an analysis of a longitudinal signal-to-noise ratio. Errors in automated segmentation remain relatively stable, and baseline error is highly likely to persist in the same direction and magnitude in subsequent time periods. However, automated segmentation (without manual refinement) is more repeatable and may be more sensitive to glaucomatous progression. Future segmentation algorithms could exploit these findings to improve automated segmentation in the future.

Subtle errors of bladder wall thickness measurement have a significant impact on the calculation of ultrasound-estimated bladder weight. A pilot study.

Ultrasound-estimated bladder weight (UEBW), is an emerging diagnostic tool, which has been used in both malesand females with lower urinary tract dysfunction. The currently acknowledged UEBW calculation methods rely on the accuratemeasurement of bladder wall thickness (BWT). We aim to identify if subtle errors in BWT measurement have a significantimpact on UEBW calculations. Twenty patients were randomly selected from an overactive bladderpatient cohort. The primary endpoint was to identify the range of false BWT measurements outside which significant changesin UEBW calculation occur. We used the Kojima method and a semi-automatic 3-D model that is based on Chalana's principle. Measurements were performed using the correct BWT and a series of faulty calculations from +0.5 mm to -0.5 mm using stepsof 0.05 mm from true BWT. The effect of a fixed 0.5 mm BWT error was checked in bladder volumes above and below 250 mland in three UEBW groups (<35 gr; 36-50 gr; >51gr). BWT measurement errors above 0.25 mm cause statistically significant changes in UEWB calculation when a 3-D model is used and errors above 0.15 mm when Kojima's method is used.At a fixed BWT error of 0.5 mm and bladder volume <250 ml, there is a 23.76% deviation from true UEBW, while at volumes>250 ml the deviation is 32.72%. The deviation is inversely proportional to the UEBW result, and heavier bladders deviateless. UEBW is a promising diagnostic tool, but small errors in BWT measurement might cause significant deviationfrom the true values. A 3-D calculation model appears to minimize such risks.

Probabilistic inverse analysis of data obtained from pavement deflection measured by FWD

FWD tests are one of the most common tests of pavement in the world. The elastic modulus of each pavement layers can be obtained by applying inverse analysis, which is useful not only in assessment of road pavement condition, but also in designing the overlayer. The author of this paper confronted probabilistic and deterministic approaches of input data for backcalculation (thickness and Poisson’s ratios of each layer) for homogeneous experimental section. The results of the sensitivity analysis have shown that the most significant influence for the identified quantity had a thickness of bituminous layers. In this paper the measurement error of thickness of asphalt concrete layers was simulated for comparison the probabilistic and deterministic approaches, moreover, the results of laboratory tests were used for verification.

Error Analysis of Indirect Broadband Monitoring of Multilayer Optical Coatings using Computer Simulations

Results of studying the errors of indirect monitoring by means of computer simulations are reported. The monitoring method is based on measuring spectra of reflection from additional monitoring substrates in a wide spectral range. Special software (Deposition Control Simulator) is developed, which allows one to estimate the influence of the monitoring system parameters (noise of the photodetector array, operating spectral range of the spectrometer and errors of its calibration in terms of wavelengths, drift of the radiation source intensity, and errors in the refractive index of deposited materials) on the random and systematic errors of deposited layer thickness measurements. The direct and inverse problems of multilayer coatings are solved using the OptiReOpt library. Curves of the random and systematic errors of measurements of the deposited layer thickness as functions of the layer thickness are presented for various values of the system parameters. Recommendations are given on using the indirect monitoring method for the purpose of reducing the layer thickness measurement error.

Error and modification in thermal barrier coatings measurement using impedance spectroscopy

In impedance spectroscopy testing of metal/ceramic multi-layers, such as thermal barrier coatings (TBCs), in order to avoid electric leakage, asymmetric electrode is widely adopted. However, how is electric field distribution in asymmetric electrode system, what error does it bring to measurement results, and how to modify these errors etc., are still not understood. In this study, electric field divergence in TBCs measurement induced by asymmetric electrode is investigated through solving a three-dimensional electric field equations numerically. The results show that the asymmetric electrode inevitably triggers divergence of electric field line, and as frequency decreases the divergence increases considerably. When Pt electrode diameter is chosen as 1mm in ceramic coating, the errors in thickness measurement for both YSZ and TGO are 26.20% and 89.3%, respectively. The errors rise as both YSZ and TGO thicknesses increase, while the errors decrease as Pt electrode size increases. The error in thickness measurement for TGO layer is much larger than that for YSZ. Through present research, a scheme to eliminate the effect of electric field divergence on measurement error is proposed.

A Novel Compensation Algorithm for Thickness Measurement Immune to Lift-Off Variations Using Eddy Current Method

Lift-off variation causes errors in the eddy current thickness measurements of metallic plates. In this paper, we have developed an algorithm that can compensate for this variation and produce an index that is linked to the thickness, but is virtually independent of lift-off. This index, termed as the compensated peak frequency, can be obtained from the measured multifrequency inductance spectral data using the algorithm we developed in this paper. This method has been derived through mathematical manipulation and verified by both the simulation and experimental data. Accuracy in the thickness measurements at different lift-offs proved to be within 2%.

Quantification of breast lesion compositions using low-dose spectral mammography: A feasibility study.

The positive predictive power for malignancy can potentially be improved, if the chemical compositions of suspicious breast lesions can be reliably measured in screening mammography. The purpose of this study is to investigate the feasibility of quantifying breast lesion composition, in terms of water and lipid contents, with spectral mammography. Phantom and tissue samples were imaged with a spectral mammography system based on silicon-strip photon-counting detectors. Dual-energy calibration was performed for material decomposition, using plastic water and adipose-equivalent phantoms as the basis materials. The step wedge calibration phantom consisted of 20 calibration configurations, which ranged from 2 to 8 cm in thickness and from 0% to 100% in plastic water density. A nonlinear rational fitting function was used in dual-energy calibration of the imaging system. Breast lesion phantoms, made from various combinations of plastic water and adipose-equivalent disks, were embedded in a breast mammography phantom with a heterogeneous background pattern. Lesion phantoms with water densities ranging from 0% to 100% were placed at different locations of the heterogeneous background phantom. The water density in the lesion phantoms was measured using dual-energy material decomposition. The thickness and density of the background phantom were varied to test the accuracy of the decomposition technique in different configurations. In addition, an in vitro study was also performed using mixtures of lean and fat bovine tissue of 25%, 50%, and 80% lean weight percentages as the background. Lesions were simulated by using breast lesion phantoms, as well as small bovine tissue samples, composed of carefully weighed lean and fat bovine tissues. The water densities in tissue samples were measured using spectral mammography and compared to measurement using chemical decomposition of the tissue. The thickness of measured and known water contents was compared for various lesion configurations. There was a good linear correlation between the measured and the known values. The root-mean-square errors in water thickness measurements were 0.3 and 0.2 mm for the plastic phantom and bovine tissue backgrounds, respectively. The results indicate that spectral mammography can be used to accurately characterize breast lesion composition in terms of their equivalent water and lipid contents.

Development of Wall-Thinning Evaluation Procedure for Nuclear Power Plant Piping—Part 1: Quantification of Thickness Measurement Deviation

Pipe wall thinning by flow-accelerated corrosion and various types of erosion is a significant and costly damage phenomenon in secondary piping systems of nuclear power plants (NPPs). Most NPPs have management programs to ensure pipe integrity due to wall thinning that includes periodic measurements for pipe wall thicknesses using nondestructive evaluation techniques. Numerous measurements using ultrasonic tests (UTs; one of the nondestructive evaluation technologies) have been performed during scheduled outages in NPPs. Using the thickness measurement data, wall thinning rates of each component are determined conservatively according to several evaluation methods developed by the United States Electric Power Research Institute. However, little is known about the conservativeness or reliability of the evaluation methods because of a lack of understanding of the measurement error. In this study, quantitative models for UT thickness measurement deviations of nuclear pipes and fittings were developed as the first step for establishing an optimized thinning evaluation procedure considering measurement error. In order to understand the characteristics of UT thickness measurement errors of nuclear pipes and fittings, round robin test results, which were obtained by previous researchers under laboratory conditions, were analyzed. Then, based on a large dataset of actual plant data from four NPPs, a quantitative model for UT thickness measurement deviation is proposed for plant conditions.

Segmentation Errors in Macular Ganglion Cell Analysis as Determined by Optical Coherence Tomography

To investigate the prevalence, features, associated factors, and reproducibility of segmentation errors in macular ganglion cell inner plexiform layer (GCIPL) thickness measurement as determined by optical coherence tomography (OCT). Cross-sectional study. Five hundred thirty-eight glaucomatous and healthy eyes from 290 subjects with OCT-measured macular GCIPL thickness were enrolled. Eyes with macular disorders, including epiretinal membrane, macular degeneration, macular hole, and myopic maculopathy, were excluded. By inspecting 128 cross-sectional OCT B-scan images per eye, the presence (yes vs. no), layer (anterior vs. posterior border), location (quadrants), and area (diffuse vs. focal) of macular GCIPL segmentation error were investigated. The effects of age, refractive error, mean deviation of visual field test, circumpapillary retinal nerve fiber layer thickness obtained by OCT, and signal strength of OCT scan on the presence of macular GCIPL segmentation errors were evaluated. In eyes with segmentation errors, repeated OCT examinations were performed to investigate the reproducibility of the segmentation errors. The prevalence, features, associated factors, and reproducibility of macular GCIPL segmentation errors were assessed. Among the 538 eyes, 52 eyes (9.7%) showed segmentation errors in macular GCIPL thickness measurement. The most common features of segmentation errors were that they affected both the anterior and posterior borders, were located at the nasal quadrant (centered to the fovea), and were diffuse. In univariate analysis, the presence of segmentation error was associated significantly with younger age (P < 0.001), higher degree of myopia (P < 0.001), and lower signal strength of OCT scan (P= 0.038). In multivariate analysis, only higher degree of myopia was associated significantly with the presence of segmentation error (P < 0.001). In repeated examinations, segmentation errors were reproducible in 24 eyes (46.2%). In other cases, the features of segmentation errors changed or disappeared. Although the OCT segmentation algorithm accurately detected macular GCIPL thickness in most eyes without macular disorders, in some cases, segmentation errors were found, especially in myopic eyes. In repeated examinations, approximately half of the errors were nonreproducible. These findings should be considered when assessing macular GCIPL thickness using OCT.

Developing an Automatic Vision based Abdominal Muscle Extraction and Analysis Method from Ultrasonography

Analyzing abdominal muscles and measuring useful associated morphological features is important in many clinical researches. While ultrasonography is a non-invasive reliable tool for such tasks, it may cause the experimenter dependent subjective diagnosis thus a computer vision based automatic muscle detector/analyzer is much needed in this area. In this paper, we propose such an automatic vision based method using a series of image processing algorithms. The novelty of our method is to extract internal oblique muscle from abdominal ultrasonographic image which was excluded in previous study due to their irregular features. Previously, we used Mask searching method to restore vague part of abdominal image but the third layer of muscle (transverse abdominis) was not clearly extracted because of the image distortion in the process. In order to analyze muscle morphometric features like the thickness, the second layer (internal oblique muscle) should also be extracted correctly thus we develop a new muscle extraction process that includes extracting the second layer by using unsharp masking. Extraction of transverse abdominis is also improved by developing a new data structure Both-Map in candidate search process. In that process, we save the morphological features of initially extracted muscle area and later such information is used to restore the fascia area with various image processing techniques to extract target muscle accurately. The effectiveness of the proposed method is verified by the practical diagnostic field of rehabilitation in the extraction accuracy and the magnitude of the muscle thickness measurement error that lies within 0.02cm in more than 60% of cases used in the experiment. Keywords: Muscle extraction, muscle analysis, abdominal ultrasonography, fascia features.

Microwave non-contact imaging of subcutaneous human body tissues.

A small-size microwave sensor is developed for non-contact imaging of a human body structure in 2D, enabling fitness and health monitoring using mobile devices. A method for human body tissue structure imaging is developed and experimentally validated. Subcutaneous fat tissue reconstruction depth of up to 70 mm and maximum fat thickness measurement error below 2 mm are demonstrated by measurements with a human body phantom and human subjects. Electrically small antennas are developed for integration of the microwave sensor into a mobile device. Usability of the developed microwave sensor for fitness applications, healthcare, and body weight management is demonstrated.

TU‐CD‐207‐02: Quantification of Breast Lesion Compositions Using Low‐Dose Spectral Mammography: A Feasibility Study

Purpose:To investigate the feasibility of measuring breast lesion composition with spectral mammography using physical phantoms and bovine tissue.Methods:Phantom images were acquired with a spectral mammography system with a silicon‐strip based photon‐counting detector. Plastic water and adipose‐equivalent phantoms were used to calibrate the system for dual‐energy material decomposition. The calibration phantom was constructed in range of 2–8 cm thickness and water densities in the range of 0% to 100%. A non‐linear rational fitting function was used to calibrate the imaging system. The phantom studies were performed with uniform background phantom and non‐uniform background phantom. The breast lesion phantoms (2 cm in diameter and 0.5 cm in thickness) were made with water densities ranging from 0 to 100%. The lesion phantoms were placed in different positions and depths on the phantoms to investigate the accuracy of the measurement under various conditions. The plastic water content of the lesion was measured by subtracting the total decomposed plastic water signal from a surrounding 2.5 mm thick border outside the lesion. In addition, bovine tissue samples composed of 80 % lean were imaged as background for the simulated lesion phantoms.Results:The thickness of measured and known water contents was compared. The rootmean‐square (RMS) errors in water thickness measurements were 0.01 cm for the uniform background phantom, 0.04 cm for non‐uniform background phantom, and 0.03 cm for 80% lean bovine tissue background.Conclusion:The results indicate that the proposed technique using spectral mammography can be used to accurately characterize breast lesion compositions.