Direct Thickness Measurements Research Articles

392 Validation of a Mathematical Model for Rupture of Spherical Intracranial Aneurysms

INTRODUCTION: An accurate mathematical model of intracranial aneurysm (IA) mechanics is of great value for its potential utility in assessing probability of IA rupture, thus informing the decision to pursue surgical intervention with its associated risks. Such a model for spherical IAs has been proposed which predicts a wall-thickness-to-IA-radius ratio (WTR) of 6.1*10-3 at which IAs rupture (Chaudhry et al. 2006). To our knowledge, no further work has been done to validate this model with clinical data. We assess the accuracy of this model using cases of ruptured and unruptured IAs. METHODS: Aneurysm height, width, neck diameter, and vessel radius were measured on CTAs/MRAs/DSAs of IAs of the basilar tip, anterior communicating, and posterior communicating arteries. Binary logistic regression analysis was performed to determine the WTR where there is a 50% probability of rupture. RESULTS: 52 unruptured and 28 ruptured spherical IAs were included. Binary logistic regression revealed a strong association between decreased WTR and rupture status. The point at which there is a 50% chance of rupture was found to be WTR = 8.6*10-3, from which the proposed 6.1*10-3 differs by only 29%. CONCLUSIONS: The model for IA rupture mechanics proposed by Chaudhry et al. agrees reasonably well with clinical data and could serve as a foundation upon which further investigation may be based. This study was limited primarily by its method of approximating aneurysm wall thickness, which may have over- or under-estimated the actual thickness. Future studies may improve on this by utilizing direct measurements of wall thickness through histological examination.

The foundations of the Patagonian icefields

The two vast Patagonian icefields are a global hotspot for ice-loss. However, not much is known about the total ice volume they store - let alone its spatial distribution. One reason is that the abundant record of direct thickness measurements has never been systematically exploited. Here, this record is combined with remotely-sensed information on past ice thickness mapped from glacier retreat. Both datasets are incorporated in a state-of-the-art, mass-conservation approach to produce a well-informed map of the basal topography beneath the icefields. Its major asset is the reliability increase of thicknesses values along the many marine- and lake-terminating glaciers. For these, frontal ice-discharge is notably lower than previously reported. This finding implies that direct climatic control was more influential for past ice loss. We redact a total volume for both icefields in 2000 of 5351 km3. Despite the wealth of observations used in this assessment, relative volume uncertainties remain elevated.

Hydrodynamic analysis of liquid microlayer formation in nucleate boiling of water

This paper presents analyses of the formation of "microlayers" i.e., very thin (∼ 1μm) liquid films often found beneath steam bubbles growing on a solid surface in low-pressure boiling. The hydrodynamics of bubble growth on a surface in pool boiling of water at atmospheric pressure have been modelled with interface-capturing Computational Fluid Dynamics (CFD) in a range of conditions that include a recent set of experiments, and transcend the remit of extant computational studies. Numerical predictions of bubble and microlayer behaviour were found in broad agreement with experimental measurements, and consistent with the current theoretical understanding of the microlayer hydrodynamic formation process. From recently reported direct measurements of microlayer thickness, a range of values of the likely thickness of the liquid film as formed on the solid surface have been inferred, and used to validate the current simulations, which clearly indicated the formation, beneath a growing steam bubble, of a liquid film of thickness comparable to values inferred from measurements. Notably, CFD simulations revealed the formation of a characteristic "dewetting ridge" i.e., an area where the film surface is markedly convex, in a microlayer region close to the triple contact line not accessible to any present-day optical measurement technique, and indicate that, in an otherwise flat microlayer, a noticeably curved region should be expected to form near the contact line. This paper provides enhanced insight into micro-scale features, such as the shape and thickness of microlayers, that typically evolve over extremely small time scales, and are therefore challenging to measure, and at present not amenable to any observation technique. A parametric study, covering a range of values of the capillary number between 7.86 × 10−4 and 7.86 × 10−2, and surface contact angles between 15˚ and 90˚, typical of wetting or partially wetting fluids on common engineering surfaces, confirmed the trends in microlayer behaviour predicted for the case of atmospheric-pressure water-boiling in laboratory conditions.

High throughput, spatially resolved thermal properties measurement using attachable and reusable 3ω sensors.

The 3ω method is a well-established thermal technique used to measure the thermal conductivity of materials and the thermal resistance of interfaces. It has significant advantages over other steady state and transient thermal techniques in its ability to provide spatially resolved thermal property measurements over a wide range of thermal conductivity. Despite its advantages, it has been restricted to lab-scale use because of the difficulty involved in sample preparation and sensor fabrication and is limited to non-metallic substrates. High-throughput 3ω measurements with reusable sensors have not been realized yet. In this work, we demonstrate a method of applying reusable 3ω sensors fabricated on flexible polyimide films to measure bulk and spatially resolved thermal properties. We establish the limits of thermal conductivity measurement with the method to be 1 to 200 W/mK, and within the measurement limit, we verify the method by comparing the measured thermal conductivities of standard samples with established values. From the 3ω measurements, we also determine the thermal resistance of an interlayer of thermal grease as a function of pressure and compare it against the resistance calculated from direct thickness measurements to demonstrate the ability of this method to provide spatially resolved subsurface information. The technique presented is general and applicable to both metallic and non-metallic substrates, providing a method for high-throughput 3ω measurements with reusable sensors and without considerable sample preparation.

Method for the refractive index of various tissues based on fluorescence microscopy

Refractive index is an important optical constant that characterizes the interaction between light and specimen. A difference in refractive index between specimen and immersion medium introduces the imaging aberration and leads to a problem that the direct thickness measurement of a specimen by optical microscopy is not accurate. However, this aberration correction still requires the exact information of the refractive index of specimen and immersion medium. Herein, we propose an imaging strategy to estimate the refractive index for an unknown specimen. A simplified diffraction model is generated to obtain the relationship between axial scaling factor and refractive index. Then regular fluorescence microscopy is performed to measure the actual axial scaling factors of specimens from mouse muscle and tumor xenograft. Referring to our theoretical plot of axial scaling factor versus refractive index, the refractive index of tissue specimen is determined. For example, we obtain a mean refractive index (n) value of 1.36 for normal muscle tissues, and 1.41 for tumor xenografts. We demonstrate that this diffraction model-based estimation method is an alternative to the current techniques, improving the accurate measurement for refractive index of tissue specimen. The simple instrument requirement with an easy specimen preparation for this estimation method of refractive index may increase the image quality on tissue specimens with less aberration.

Simulation of Layer Thickness Measurement in Thin Multi-Layered Material by Variable-Focus Laser Ultrasonic Testing

Thin multi-layered materials are widely used in key structures of many high technology industries. To ensure the quality and safety of structures, layer thickness measurement by non-destructive testing (NDT) techniques is essential. In this paper, a novel approach for the measurement of each layer's thickness in thin multi-layered material is proposed by using ring-shaped laser generated focused ultrasonic bulk waves. The proposed method uses a ring-shaped laser with a variable radius to generate shear waves with variable focus inside the structure. By analyzing the signal characteristics at the ring center when the laser radius varies from zero to maximum, the direct measurement of layer thickness can be realized, considering that only when the focal depth and the layer thickness satisfy the specific relationship, the reflected shear waves converge and form a peak at the ring center. This straightforward approach can increase the pulse-echo SNR and prevent the processing of aliasing signals, and therefore provides higher efficiency and accuracy for the layer thickness measurement. In order to investigate the feasibility of this method, finite element simulations were conducted to simulate the ring-shaped laser generated ultrasonic waves in multi-layered structure in detail. Following the principle of the proposed method, the layer thickness of a bi-layer and 3-layer structure were respectively measured using simulation data. The results confirm that the proposed method can accurately and efficiently measure the layer thickness of thin multi-layered material.

Direct measurement of boundary layer thickness on ion-exchange membrane surfaces during reverse electrodialysis

The concentration distribution and thickness of the boundary layer on the membrane surface during electrodialysis were studied using the double electrode potential analysis method.

Effect of culture depth on the shell thickness of the blue mussel Mytilus edulis: a practical case study comparing direct and indirect methods of measurement

ABSTRACT Mytilus species have a fundamental role in coastal environments and constitute an important aquaculture resource. Their shell has a protective function and is affected by multiple factors, such as the size of the animal, density, environmental characteristics and presence of predators. It is crucial to accurately estimate shell thickness in order to understand the effects of the ever-changing environment on mussel physiology, morphology and ecology. This study compares a newly developed direct method for measuring shell thickness, using scanning electron microscopy (SEM), and a widely used indirect method (shell thickness index, STI), in the context of a practical case study of the blue mussel Mytilus edulis. In this study, STI did not appear as highly correlated to direct thickness measurement as in previous studies. This study also showed a weaker relationship between measured shell length and STI. In the case study, assessing the effect of culture depth on M. edulis growth and condition, STI showed a significant variation with depth, while SEM measured thickness did not. Therefore, the choice to use STI vs direct measurement of shell thickness drastically changed the results and interpretation of the case study. This work highlights the importance of a carefully designed method for measuring shell thickness and emphasizes that, before application, indirect methods should be quality controlled for the population studied. However, when high precision is needed for shell thickness measurements the application of SEM-based techniques may be necessary. This is the first study where SEM-based techniques have been used to measure shell thickness in M. edulis.

Cartilage assessment using preoperative planning MRI for femoral component rotational alignment

BackgroundSurgical planning of posterior referencing total knee arthroplasty (TKA) using computed tomography (CT) might lead to over-rotation of the femoral component because CT could not detect cartilage thickness of the posterior femoral condyle. The purpose of this study was to examine the rotational alignment difference of the femoral component between magnetic resonance imaging (MRI) and CT. MethodsFor elderly varus osteoarthritic patients, 66 varus osteoarthritic knee patients that underwent primary TKA were selected. Twenty-seven young patients who underwent primary anterior cruciate ligament reconstruction were selected as control. After the transepicondylar axis (CEA), the surgical epicondylar axis (SEA) and the posterior femoral condylar line (PCL) were drawn on CT and on MRI at the same angles as CT. Then, the practical PCL was drawn on MRI considering the cartilage thickness (the cartilage PCL). The angle between the SEA and the cartilage PCL (the cartilage posterior condylar angle (PCA)) was measured as preoperative planning. To investigate the accuracy of preoperative MRI measurement, the cartilage thickness on posterior femoral condyles was directly measured during TKA. ResultsThe cartilage PCA for varus osteoarthritic patients averaged 1.3 ± 1.3°. The cartilage PCA was 1.8 ± 1.0° significantly smaller than the bone PCA (the PCA measured on CT). Meanwhile, the cartilage PCA was 0.2 ± 0.4° significantly larger than the bone PCA in young people. The preoperative angle measurement on MRI strongly correlated with the direct measurement of cartilage thickness during TKA. ConclusionThere was 1.8° of divergence between MRI and CT in varus osteoarthritic patients due to cartilage degeneration of the medial femoral condyle. Cartilage assessment using MRI was useful for femoral component rotational alignment.

A model for spectroscopic ellipsometry analysis of plasma-activated Si surfaces for direct wafer bonding

In this work, the impact of plasma treatment on Si wafers with native oxide on top was systematically investigated using spectroscopic ellipsometry. A general applicable three-layer optical model structure for ellipsometry data fitting was developed and employed on samples treated with the N2, O2, and N2/O2 mixture plasma. Oxide-growth, amorphization of crystalline Si, and the formation of a transition layer between the SiO2 and the amorphous Si were detected. The estimated thicknesses of produced layers were confirmed by complementary methods, which allow precise ultra-thin layers thicknesses detection, namely, angle-resolved x-ray photoelectron spectroscopy and transmission electron microscopy. The depth-resolved chemical composition and the direct thickness measurements of the produced amorphous structure revealed pronounced elemental gradients and the absence of sharp interfaces. Nitrogen gas used in the plasma process was found to be implanted mainly at the interface of the SiO2/transition layer in the form of Si3N4. However, it was verified that it is feasible to employ one general ellipsometry model consisting of SiO2/transition layer/amorphous Si on crystalline Si for all plasma species due to comparably low Si3N4 concentrations as well as its refractive index n and absorption k similarity to SiO2. Spectroscopic ellipsometry is nondestructive and can be efficiently applied to analyze whole wafers without any sample preparation. It can be concluded that the present approach to ellipsometry model development and verification is well suited for plasma-activated direct wafer bonding processes.

A Systematic Review of The Effects of Different Resistance Training Volumes on Muscle Hypertrophy.

The main goal of this study was to compare responses to moderate and high training volumes aimed at inducing muscle hypertrophy. A literature search on 3 databases (Pubmed, Scopus and Chocrane Library) was conducted in January 2021. After analyzing 2083 resultant articles, studies were included if they met the following inclusion criteria: a) studies were randomized controlled trials (with the number of sets explicitly reported), b) interventions lasted at least six weeks, c) participants had a minimum of one year of resistance training experience, d) participants’ age ranged from 18 to 35 years, e) studies reported direct measurements of muscle thickness and/or the cross-sectional area, and f) studies were published in peer-review journals. Seven studies met the inclusion criteria and were included in the qualitative analysis, whereas just six were included in the quantitative analysis. All participants were divided into three groups: “low” (<12 weekly sets), “moderate” (12-20 weekly sets) and “high” volume (>20 weekly sets). According to the results of this meta-analysis, there were no differences between moderate and high training volume responses for the quadriceps (p = 0.19) and the biceps brachii (p = 0.59). However, it appears that a high training volume is better to induce muscle mass gains in the triceps brachii (p = 0.01). According to the results of this review, a range of 12-20 weekly sets per muscle group may be an optimum standard recommendation for increasing muscle hypertrophy in young, trained men.

Simultaneous retention of organic and inorganic contaminants by a ceramic nanofiltration membrane for the treatment of semiconductor wastewater

The semiconductor manufacturing industry produces large amounts of ammonia-contaminated wastewaters which require costly and energy-intensive treatments. This study demonstrates the application of a commercially available ceramic nanofiltration (NF) membrane for the control of organic and inorganic contaminants as well as ammonium retention in the treatment of semiconductor wastewater. Analysis of the hydrodynamic pore transport model based on the direct measurement of membrane thickness in the active layer indicated that the ceramic NF membrane has an average pore radius of ≈0.65 nm. Zeta potential measurements of the ceramic NF membrane showed that the membrane surface was negatively charged at neutral pH. The ammonium retention capacity of the ceramic NF membrane was evaluated using a single symmetric ammonium salt solution (1.8 mM NH4HCO3; i.e., the average ammonium concentration in semiconductor wastewater) and combined salt solutions (mixtures of 1.8 mM NH4HCO3 and either 2.0 mM of Na2SO4, CaSO4, or CaCl2). The combined NH4HCO3 and Na2SO4 solution rendered a remarkably high ammonium retention rate of 88.7%, which was attributed to higher valency co-ions (SO42-) in this solution with the same negative surface charge of the ceramic NF membrane. In contrast, the calcium ions (Ca2+) in different combined salt solutions containing CaSO4 and CaCl2 interfered with ammonium retention. We further employed the ceramic NF membrane to treat semiconductor wastewater samples taken from a full-scale semiconductor wastewater treatment plant and demonstrated that this proposed treatment method could effectively retain organic and inorganic contaminants with a low fouling propensity. Our results highlight the promising potential of ceramic NF membranes for the treatment of industrial wastewaters with diverse organic and inorganic contaminants.

Estimating extreme level ice and ridge thickness for offshore wind turbine design: Case study Kriegers Flak

AbstractWhen designing offshore wind turbines in ice‐covered seas, site‐specific ice conditions present crucial input for the structural design. In this study, methods of estimating the maximum level ice thickness occurring once in 50 years and parameters of a design ice ridge in an area where no direct ice thickness measurements exists are presented. The site of Kriegers Flak at the Southern Baltic Sea is taken as a case study. Rather than just applying basic equations found from the standards, the method gives more detailed estimates by utilizing available ice chart information, ice reports and atlases together with measured air temperature data to estimate the starting and ending date of ice growth. The maximum level ice thickness occurring once in 50 years at the site of Kriegers Flak wind farm was estimated to be between 0.26 and 0.44 m depending on the assumptions. The effect of the studied history length, the utilized weather station and the use of snow thicknesses to the 50‐year ice thickness estimates are compared and discussed. Interaction with ice ridges was found to be a relevant but infrequent, load scenario for the site of Kriegers Flak. For this reason, a representative ridge for determining ice ridge loads is presented. The most important parameter in a ridge, the thickness of the consolidated layer, was found based on scenario analyses to be in a range between 0.43 and 0.67 m can be used to calculate ice loads against the wind turbine substructures.

OF-UMRN: Uncertainty-guided multitask regression network aided by optical flow for fully automated comprehensive analysis of carotid artery.

Fully automated comprehensive analysis of carotid artery (localization of range of interest (ROI), direct quantitative measurement and segmentation of lumen diameter (CALD) and intima-media thickness (CIMT), and motion estimation of the carotid wall) is a reliable auxiliary diagnosis of cardiovascular diseases, which relieves physicians from laborious workloads. No work has achieved fully automated comprehensive analysis of carotid artery due to five intractable challenges: (1) The heavy reliance on experienced carotid physicians for the selection of ROI limits fully automated studies. (2) The weak structural information of intima-media thickness increases the difficulty of feature encoding. (3) The radial motion of the carotid wall results in the lack of discriminant features of boundaries. (4) Diseased carotid arteries lose many expression features. (5) Optimal weights of multitask regression are hard to tune manually. In this paper, we propose a novel uncertainty-guided multitask regression network aided by optical flow named OF-UMRN to solve the intractable challenges. The four modules and three innovations of the OF-UMRN take their responsibility. OF-UMRN takes localization and mapping of ROI as a pre-processing. It achieves direct quantitative measurement and segmentation by a multitask regression network. And we creatively model homoscedastic uncertainty to automated tune the weights of the two tasks optimally. The OF-UMRN adopts a bidirectional mechanism to encode the optical flow used to predict the carotid wall's motion fields. More importantly, we creatively propose a dual optimization module based on the co-promotion between segmentation and motion estimation to improve the performance of radially moving and diseased carotid arteries. Therefore, the OF-UMRN makes the most of the pathological relationship between multiple objects and co-promotion between various tasks. Extensive experiments on US sequences of 101 patients have demonstrated the superior performance of OF-UMRN on the fully automated comprehensive analysis of the carotid artery. Therefore the OF-UMRN has excellent potential in clinical disease diagnoses and assessments of the carotid artery.

Comparison of direct measurements of sea ice thickness and snow height, CryoSat-2 observations and PIOMAS numerical estimates

The paper presents the results of comparison of contact measurements of ice thicknesses and snow heights performed at the points of the hydrological stations of the “Transarktika-2019” expedition in April 2019 north of Franz-Josef Land archipelago, with altimetry observations of the Cryosat-2 satellite and numerical estimates of the PIOMAS (Pan-Arctic numerical Ice and Ocean Modeling system and data Assimilation). A significantly better correspondence is predictably shown between the variability of the ice thickness directly measured and observed using the CryoSat-2 satellite than that for the numerical PIOMAS system estimates. A trial correction of the algorithm for calculating the ice thickness by replacing the climatic values of the ice density, snow density and height with data from direct measurements also predictably improves the quality of calculating the ice thickness from satellite observations. The mean / route mean square differences obtained for ice thicknesses (+44/+96 cm for uncorrected and +30/+95 cm for corrected CryoSat-2 satellite, –14/+81 cm for PIOMAS system) and snow height (–4/+12 cm for CryoSat-2 satellite, –15/+12 cm for PIOMAS system) show the scale of uncertainty in estimating sea ice thickness and snow height for areas dominated by medium and thick first-year ice. An anomaly of the ice thicknesses observed during the expedition is given in comparison with the background characteristics based on historical ice charting data for 1970s — 1990s, earlier High-Arctic aircraft “Sever” expeditions during 1950s — 1970s and the stated remote observations and numerical estimates for 2000s — 2019. Comparison shows that the AARI expedition was actually carried out in one of the most favorable years for ice research in the last decade for this region — the average ice thickness in April 2019 was 15 — 28 cm higher than that for the interval 2011 — 2019 with a slightly lower (1 — 2 cm) height of the snow cover. In the earlier period of the 1970 — 1990s this area was characterized by significantly thicker old ice with characteristic thicknesses ~ 60 cm more than in April 2019.

Grease film thickness measurement in rolling bearing contacts

Rolling bearings are the second most used machine components. They work in what it is called elastohydrodynamic lubrication regime. The geometry of rolling element bearings makes the direct measurement of the lubricant film thickness a challenging task. Optical interferometry is widely used in laboratory conditions for studying elastohydrodynamic lubrication however it cannot be used directly in rolling element bearings thus the only suitable methods are electrical techniques. Of these, film thickness measurement based on electrical capacitance of the contacts has been used in the past by a number of authors. One of the limitations of the capacitance method, when used in rolling bearings, is that it cannot distinguish between the contacts of every rolling element and raceway on one hand and on the other between the inner and outer ring contacts. In the present study the authors used an original test rig which can measure the film thickness for only one ball and separately for the inner and outer rings of a radial ball bearing. This paper thus shows for the first-time results of the lubricant film thickness, at the inner and outer raceways, in grease lubricated rolling bearings.

Arborescent lycopsid periderm production was limited.

Late Paleozoic arborescent lycopsids have been thought to have grown from sporelings into large trees through the production of a periderm cylinder, particularly massive in the proximal portion of the trunk and tapering distally, with this rind of bark providing most of their structural support. Here, we argue that physiological limitations would have prohibited the production of thick periderm and test this hypothesis using multiple independent lines of evidence derived from anatomical permineralization and surface impression fossils that allow both direct and indirect measurement of periderm radial thickness. Across all six genera of Pennsylvanian arborescent lycopsids that were investigated, all evidence indicates limited periderm production: typically < 5cm, always <15cm, even in trunks that would have reached 1m or more in diameter. The large amount of arborescent lycopsid periderm in Middle Pennsylvanian coals represents taphonomic enrichment rather than a true anatomical signal, complicating interpretation of their biology including biomechanics and early ontogeny.

Deterioration of bone microstructure by aging and menopause in Japanese healthy women: analysis by HR-pQCT.

Second-generation high-resolution peripheral quantitative computed tomography (HR-pQCT) has provide higher quality of bone images with a voxel size of 61µm, enabling direct measurements of trabecular thickness. In addition to the standard parameters, the non-metric trabecular parameters such as trabecular morphology (plate to rod-like structures), connectivity, and anisotropy can also be analyzed. The purpose of this study is to investigate deterioration of bone microstructure in healthy Japanese women by measuring standard and non-metric parameters using HR-pQCT. Study participants were 61 healthy Japanese women (31-70years). The distal radius and tibia were scanned using second-generation HR-pQCT, and microstructures of trabecular and cortical bone were measured. Non-metric trabecular parameters included structure model index (SMI), trabecular bone pattern factor (TBPf), connectivity density (Conn.D), number of nodes (N.Nd/TV), degree of anisotropy (DA), and star volume of marrow space (V*ms). Estimated bone strength was evaluated by micro finite element analysis. Associations between bone microstructure, estimated bone strength, age, and menopause were analyzed. Trabecular number declined with age, and trabecular separation increased. SMI and TBPf increased, Conn.D and N.Nd/TV declined, and V*ms increased. Cortical BMD and thickness declined with age, and porosity increased. Stiffness and failure load decreased with age. Cortical thickness and estimated bone strength were affected by menopause. Cortical thickness was most associated with estimated bone strength. Trabecular and cortical bone microstructure were deteriorated markedly with age. Cortical thickness decreased after menopause and was most related to bone strength. Non-metric parameters give additional information about osteoporotic changes of trabecular bone.

Validation of Micromechanical Model for Prediction of ITZ Thickness of High-Strength Concrete Containing Secondary Cementitious Materials

The mechanical properties of a cementitious composite are strongly affected by interfacial transition zone (ITZ) between the matrix and the aggregates, mainly by its strength and thickness. A micromechanical model based on Mori-Tanaka scheme coupled with an estimation of deviatoric stress in ITZ was developed for evaluation of the effect of selected secondary cementitious materials (SCMs – silica fume, fly ash and metakaolin) on the properties of ITZ in high-strength concrete (HSC). The model was validated by means of comparison of predicted ITZ thickness with direct ITZ thickness measurements performed by a combination of scanning electron microscopy and grid nanoindentation. Very good agreement between the theoretical and experimental results was reached, therefore the developed micromechanical model can be used for further research and optimization of HSC containing SCMs. Silica fume was determined to be the most efficient supplementary cementitious material from the point of view of ITZ thickness reduction.

Direct measurement of TEM lamella thickness in FIB-SEM.

Transmission electron microscope (TEM) specimen preparation by focused ion beam (FIB) milling requires delicate polishing of a thin window of material during the final stages of the procedure. Over or underpolishing is common and requires extra microscope resources to correct. Despite some methods for lamella thickness measurement being available, the majority of users judge the final polishing step subjectively from scanning electron microscope (SEM) images acquired between milling steps. Here we demonstrate successful thickness determination of thin silicon lamellae using calibrated secondary electron detectors in a FIB-SEM dual-beam chamber. Unlike previous thickness measurement methods it does not require long acquisition times, the use of in-chamber scanning transmission electron microscope (STEM) or energy dispersive x-ray spectroscopy detectors. The calibration aligns a SEM image to an electron energy loss spectroscopy (EELS) map of lamella thickness acquired in a TEM. This calibration reveals the greyscale-thickness dependence of two secondary electron SEM detectors: the through-lens detector (TLD) and the in-chamber electron detector (ICE). It was found that lamella thickness estimation for TLD images is accurate for areas thinner than 0.4 t/λ, whilst ICE images are most accurate for areas thicker than 0.5 t/λ up to 1.1 t/λ. The procedure presented here allows objective lamella thickness determination during the final stages of FIB specimen preparation using conventional imaging modes for common secondary electron detectors. LAY DESCRIPTION: Successful analysis of a material in a transmission electron microscope requires very thin windows of the material to be fabricated. Despite the quality of this analysis relying heavily on the thickness of the window, measuring thickness during window fabrication is not common practice. The authors show that it is possible to measure the thickness of the window directly in a focused-ion-beam chamber with a scanning electron microscope without altering the fabrication procedure, and using electron detectors common to most microscopes.