Accurate Density Measurements Research Articles

Localized time accurate sampling of nonequilibrium and unsteady hypersonic flows: methods and horizons

Modern “non-intrusive” optical methods are providing revolutionary capabilities for diagnostics of hypersonic flow fields. They generate accurate information on the performance of ground test facilities and provide local time accurate measurements of near-wall and off-body flow fields surrounding hypersonic test articles. They can follow the true molecular motion of the flow and detect nonequilibrium states and gas mixtures. They can be used to capture a wide range of turbulent scales and can produce highly accurate velocity, temperature and density measurements as well as time-frozen images that provide intuitive understanding of flow phenomena. Recent review articles address many of these methods and their applications. The methods highlighted in this review are those that have been enabled or greatly improved by new, versatile laser systems, particularly including kHz rate femtosecond lasers and MHz rate pulse burst lasers. Although these methods can be applied to combusting environments, the focus of this review is on external high Mach number flows surrounding test articles and wind tunnel core flow properties. The high repetition rates enable rapid time evolving flows to be analyzed and enable the collection of large data sets necessary for statistical analysis. Future capabilities based on the use of atomic vapor filters and on frequency tunable, injection locked MHz rate lasers are promising.

LiDAR-sensed tree canopy correction in uneven terrain conditions using a sensor fusion approach for precision sprayers

Precision spraying is one of the most promising techniques to produce healthy and sustainably profitable crops. However, accurate canopy density measurements for precision spraying decisions are still a challenging endeavor, especially in orchards with uneven terrain conditions. A sensor fusion-based canopy point correction system was developed with a 3D light detection and ranging (LiDAR) sensor and an inertial navigation system-global navigation satellite system (INS-GNSS) for accurate tree canopy density measurement. The LiDAR sensor was used to acquire the tree canopy architectures, while the INS-GNSS sensor was to evaluate the terrain slopes and the tree georeferenced locations. A mathematical model was developed to perform the simulation for correction of canopy points based on given changes in the roll, pitch, and yaw angles. A sensor fusion algorithm was developed to process the canopy point corrections for the tree fruit orchards with three different sloping conditions, including longitudinal, lateral, and combination of both slopes. Simulation results reported that the developed model established the correction of tree canopy points with varying roll, pitch, and yaw angles. Field evaluation results suggested that the developed system could be used for correcting canopy points at any sloping conditions in various terrains. The measured tree canopy density from the corrected canopy points reported a possible of off-target chemical reduction up to 13.87%, 5.19%, and 15.45% in orchard sites 1, 2 and 3, respectively. With the accurate tree canopy density measurement, it is anticipated that the developed system could be used to reduce the off-target deposition for precision spraying applications in uneven tree fruit orchards.

On the role of orifice wetting for Al and Al22.5 wt%Cu with Al2O3 in the discharge crucible method

The demand to develop Materials Genomics and Integrated Materials Computation requires the availability of high temperature liquid metals property data. As computing power and algorithms are constantly being improved, the accuracy of thermophysical property data has emerged as one of the limiting factors. Knowledge of these properties for materials such as Al and Al-alloys is a critical factor in numerical simulations and modelling of a wide array of industrial processes. This work reports on the measurement of viscosity, surface tension and density of liquid Al and Al-22.5wt.%Cu using the discharge crucible method. While viscosity and surface tension proved to be in good agreement with other published experimental data, as well as various theoretical and empirical models, density was found to be significantly lower than expected or previously measured. With further analysis, it was determined that wetting of Al or Al-Cu at the orifice of the Al2O3 crucible had a significant effect on flow rate; ergo, violating some of the key assumptions in the model used to calculate the thermophysical properties. Dimensionless number analysis identified that wetting had an immediate effect on the flow rate due to the formation of a meniscus, with the effect becoming more dominant as Capillary number decreased or drain time increased. In looking at the sensitivity of the model, it was determined that density had the largest influence on flow rate, explaining the unique link between the role of orifice wetting and density measurement accuracy (as opposed to viscosity or surface tension). Future research will aim to extend the discharge crucible model and method to account for wetting at the orifice, particularly at high temperatures.

Getting to the root of the problem: improving measurements of mangrove belowground production and carbon sequestration.

This article is a Commentary on Arnaud et al. (2021), 232: 1591–1602.

In-line characterisation of continuous phase conductivity in slurry flows using artificial intelligence tomography

Electrical Impedance Tomography (EIT) can be applied to monitor a variety of mineral and chemical processes including: velocity measurements in drilling cuttings and hydrocyclone operations. Hydraulic conveying systems rely upon the knowledge of slurry density to ensure efficient transportation of the solids. Typically, density measurements exploit the attenuation of gamma ray photons which poses complex safety, operational and regulatory concerns with Electrical Impedance Tomography affording a non-nuclear alternative to traditional approaches. To optimise the accuracy of this non-nuclear density measurement, the electrical conductivity of the aqueous phase in a multi-component slurry, is required. Whilst conductivity probes are sufficiently accurate, there are often drawbacks and limitations due to installation restrictions, as it is difficult to separate aqueous and solid phases in real-time. Electrical Impedance Fingerprinting (EIF), is a novel measurement technique which characterises formulation properties, in-situ, based upon electrical impedance sensing and artificial intelligence algorithms. This paper outlines the development of EIF and its application to monitor aqueous phase conductivity in multi-component slurries, containing sands and clays. EIF accurately predicts this conductivity with high accuracy and a root-mean squared error of 0.055 mS cm−1. This development ensures accurate non-nuclear density measurements (<5%) are obtained across an extended aqueous electrical conductivity range of 1.5–70 mS cm−1. This encompasses the majority of target hydraulic conveying systems in mining operations. EIF also enhances the functionality of ‘traditional’ electrical tomography as not only are mineral processes able to be visualised, but the process materials are simultaneously characterised, to improve process understanding, optimisation and control.

Excess properties of binary mixtures of tri–iso-amyl phosphate + n–hexane (or n-dodecane): Physical significance of coefficients of Redlich-Kister type equation

Present study incorporates thermodynamic analysis of data obtained by accurate measurement of density and viscosity of binary liquid mixtures of tri–iso-amyl phosphate and n–hexane (or n–dodecane). Law of density and viscosity of binary liquid mixtures is given as follows: Density and logarithmic viscosity of binary mixtures are nth (1≤n≤4) order polynomials of mole fraction of one of the component at constant temperature, and parametric coefficients of such polynomials are mth (1≤ m≤3) order polynomials of absolute temperature. A dimensionless Redlich–Kister equation (RK-EoS) of state is introduced to decipher physical significance of coefficients of RK-Eqn, by comparing with the same order of Virial equation of state (Virial-EoS). Physical significance of coefficients of RK-EoS is similar to that of significance of virial-coefficients in thermodynamic Virial Equation, in terms of molecular interactions. Parametric coefficients of RK-EoS are directly proportional to the corresponding virial coefficient of Virial–EoS and inversely proportional to both mole fraction difference and molar volume of mixture of the same order of virial coefficient. Coefficients of Vogel’s equation of viscosity have been found to be polynomial of mole fraction of one of the component of binary mixtures.

A new method for the study of biophysical and morphological parameters in 3D cell cultures: Evaluation in LoVo spheroids treated with crizotinib

Three-dimensional (3D) culture systems like tumor spheroids represent useful in vitro models for drug screening and more broadly for cancer biology research, but the generation of uniform populations of spheroids remains challenging. The possibility to properly characterize spheroid properties would increase the reliability of these models. To address this issue different analysis were combined: i) a new device and relative analytical method for the accurate, simultaneous, and rapid measurement of mass density, weight, and size of spheroids, ii) confocal imaging, and iii) protein quantification, in a clinically relevant 3D model. The LoVo colon cancer cell line forming spheroids, treated with crizotinib (CZB) an ATP-competitive small-molecule inhibitor of the receptor tyrosine kinases, was employed to study and assess the correlation between biophysical and morphological parameters in both live and fixed cells. The new fluidic-based measurements allowed a robust phenotypical characterization of the spheroids structure, offering insights on the spheroids bulk and an accurate measurement of the tumor density. This analysis helps overcome the technical limits of the imaging that hardly penetrates the thickness of 3D structures. Accordingly, we were able to document that CZB treatment has an impact on mass density, which represents a key marker characterizing cancer cell treatment. Spheroid culture is the ultimate technology in drug discovery and the adoption of such precise measurement of the tumor characteristics can represent a key step forward for the accurate testing of treatment's potential in 3D in vitro models.

Measurements of Density of Liquid Oxides with an Aero-Acoustic Levitator.

Densities of liquid oxide melts with melting temperatures above 2000 °C are required to establish mixing models in the liquid state for thermodynamic modeling and advanced additive manufacturing and laser welding of ceramics. Accurate measurements of molten rare earth oxide density were recently reported from experiments with an electrostatic levitator on board the International Space Station. In this work, we present an approach to terrestrial measurements of density and thermal expansion of liquid oxides from high-speed videography using an aero-acoustic levitator with laser heating and machine vision algorithms. The following density values for liquid oxides at melting temperature were obtained: Y2O3 4.6 ± 0.15; Yb2O3 8.4 ± 0.2; Zr0.9Y0.1O1.95 4.7 ± 0.2; Zr0.95Y0.05O1.975 4.9 ± 0.2; HfO2 8.2 ± 0.3 g/cm3. The accuracy of density and thermal expansion measurements can be improved by employing backlight illumination, spectropyrometry and a multi-emitter acoustic levitator.

Analysis of Lateral Fluid Gradients From DFA Measurements and Simulation of Reservoir Fluid Mixing Processes Over Geologic Time

Downhole fluid analysis (DFA) is one pillar of reservoir fluid geodynamics (RFG). DFA measurements provide both vertical and lateral fluid gradient data. These gradients, especially the asphaltene gradient derived from accurate optical density (OD) measurements, are critical in thermodynamic analysis to assess equilibration level and identify RFG processes. Recently, an RFG study was conducted using DFA and laboratory data from an oil field in the Norwegian North Sea. Fluid OD gradients show equilibrated asphaltenes in most of the reservoir, with a lateral variation of 20%. This indicates connectivity, which is confirmed by three years of production data. Two outliers are off the asphaltene equilibrium curve implying isolated sections, one each on the extreme east and west flank. Their asphaltene fraction varies by a factor of six. Such a difference reveals that different charge fluids entered the reservoir, and the equilibrated asphaltenes are the result of an after-charge mixing process. Meanwhile, different gas-oil contacts (GOCs) exist in the reservoir, indicating a lateral solution-gas gradient. Geochemistry analysis shows the same level of mild biodegradation in all the fluid samples, including those from two isolated sections. This means that biodegraded oil spills into the whole reservoir with little or no in-reservoir biodegradation. Furthermore, lateral asphaltene gradients at different times after charge have been preserved; it was a factor of six in asphaltenes content initially and is now 20% in the present day. This unique data set provides a valuable constraint to simulate reservoir fluid after-charge mixing processes to present day, aiming to investigate the factors impacting the evolution of lateral composition gradients in geologic time in a connected reservoir. Numerical simulations were performed over geologic time in reservoirs filled by oil with a lateral density gradient, which imitates the lateral compositional gradients in the gas-oil ratio (GOR) and asphaltenes measured in the above oil field. Simulations show that this lateral gradient creates lateral differential pressures and causes a countercurrent fluid flow forming a convection cell. In reservoirs with realistic vertical-to-horizontal aspect ratios, such fluid flows are not rapid, and lateral gradients can be partially retained in moderate geologic times. Additionally, diffusion was included in the simulation. The reservoir model was initialized with two GOCs producing subtle lateral GOR and density gradients. The simulated mixing process transports gas from higher GOR regions to lower GOR regions and reduces the GOC difference. However, the flux of solution gas transport is small. Consequently, we conclude that lateral GOR and asphaltene gradients can persist for moderate geologic time, which is consistent with observation from the field.

Experimental and modeling studies of density and viscosity behavior of a live fluid due to CO2injection at reservoir condition

In this study, highly accurate measurements of density and dynamic viscosities of a recombined live oil and its mixture with additional CO2were performed. The experiments were carried out under pressure and temperature gradients found in Brazilian Pre-salt reservoirs, that is, in the pressure range from (27.6 to 68.9) MPa and at (333.15 and 353.15) K. The assumption of volume change on mixing is evaluated from the experimental results, and the influence of pressure and temperature on the volume change upon mixing is assessed. The densities of mixtures are calculated considering (i) the excess volume approach, and (ii) no volume change. The densities are better correlated using the excess volume approach with Average Absolute Deviations (AAD) of 0.03%. Thirteen mixing rules of viscosity are examined by comparing the predicted values with the experimental viscosity of the recombined live oil + CO2mixture. The performance of some rules using compositional fractions (molar, volume and weight) is also evaluated. Thus, a total of 28 different ways to calculate the mixture viscosities were tested in this study. The worst result was obtained with Bingham’s method, leading to 148.6% AAD. The best result was obtained from Lederer’s method with 2% AAD and a maximum deviation of 5.8% using volume fractions and the fitting parameterα. In addition, deviations presented by the predictive methods of Chevron, Double log, and Kendall did not exceed 9% AAD, using weight fractions (Chevron and Double log) and molar fractions (Kendall and Monroe).

Development of methods for determining the density of low-melting metals

Features of the formation and development of scientific research in the laboratory of physics of interfacial phenomena in ChISU named after L. N. Tolstoy in the 1970-1980s of the last century are considered in this paper. Particular attention is paid to the development and improvement of various methods for measuring the density of liquid metals and alloys. We determined the contribution of ChSU scientists in the study of metals and alloys properties and gave a scientific assessment of the obtained results. The development of methods and techniques for measuring the density of liquid metals and alloys went in two directions. Primarily, we took significant steps towards improving the accuracy of density measurements. The instruments were designed in which the accuracy of measuring density and, in particular, the temperature coefficient of density was significantly increased. Foremost, this concerns advanced pycnometers and areometers designed in ChSU laboratories. The instruments received inventor’s certificates, and they were awarded the bronze medal of the Exhibition of Achievements of National Economy in 1977. The second direction improving the measuring technique of the metal properties is characterized by instrument designing for the joint measurement of physico-chemical properties in the same thermal vacuum conditions. Both areometers and pycnometers were used to determine density in these instruments.

Important pharmacokinetic parameters for individualization of 177 Lu-PSMA therapy: A global sensitivity analysis for a physiologically-based pharmacokinetic model.

The knowledge of the contribution of anatomical and physiological parameters to interindividual pharmacokinetic differences could potentially be used to improve individualized treatment planning for radionuclide therapy. The aim of this study was therefore to identify the physiologically based pharmacokinetic (PBPK) model parameters that determine the interindividual variability of absorbed doses (ADs) to kidneys and tumor lesions in therapy with 177 Lu-labeled PSMA-targeting radioligands. A global sensitivity analysis (GSA) with the extended Fourier Amplitude Sensitivity Test (eFAST) algorithm was performed. The whole-body PBPK model for PSMA-targeting radioligand therapy from our previous studies was used in this study. The model parameters of interest (input of the GSA) were the organ receptor densities [R0 ], the organ blood flows f, and the organ release rates λ. These parameters were systematically sampled NE times according to their distribution in the patient population. The corresponding pharmacokinetics were simulated and the ADs (model output) to kidneys and tumor lesions were collected. The main effect and total effect were calculated using the eFAST algorithm based on the variability of the model output: The main effect of input parameter represents the reduction in variance of the output if the "true" value of parameter would be known. The total effect of an input parameter represents the proportion of variance remaining if the "true" values of all other input parameters except for are known. The numbers of samples NE were increased up to 8193 to check the stability (i.e., convergence) of the calculated main effects and total effects . From the simulations, the relative interindividual variability of ADs in the kidneys (coefficient of variation CV=31%) was lower than that of ADs in the tumors (CV up to 59%). Based on the GSA, the most important parameters that determine the ADs to the kidneys were kidneys flow ( =0.36, =0.43) and kidneys receptor density ( =0.25, =0.30). Tumor receptor density was identified as the most important parameter determining the ADs to tumors ( and up to 0.72). The results suggest that an accurate measurement of receptor density and flow before therapy could be a promising approach for developing an individualized treatment with 177 Lu-labeled PSMA-targeting radioligands.

Model-based dual-energy tomographic image reconstruction of objects containing known metal components

Dual-energy (DE) decomposition has been adopted in orthopedic imaging to measure bone composition and visualize intraarticular contrast enhancement. One of the potential applications involves monitoring of callus mineralization for longitudinal assessment of fracture healing. However, fracture repair usually involves internal fixation hardware that can generate significant artifacts in reconstructed images. To address this challenge, we develop a novel algorithm that combines simultaneous reconstruction-decomposition using a previously reported method for model-based material decomposition (MBMD) augmented by the known-component (KC) reconstruction framework to mitigate metal artifacts. We apply the proposed algorithm to simulated DE data representative of a dedicated extremity cone-beam CT (CBCT) employing an x-ray unit with three vertically arranged sources. The scanner generates DE data with non-coinciding high- and low-energy projection rays when the central source is operated at high tube potential and the peripheral sources at low potential. The proposed algorithm was validated using a digital extremity phantom containing varying concentrations of Ca-water mixtures and Ti implants. Decomposition accuracy was compared to MBMD without the KC model. The proposed method suppressed metal artifacts and yielded estimated Ca concentrations that approached the reconstructions of an implant-free phantom for most mixture regions. In the vicinity of simple components, the errors of Ca density estimates obtained by incorporating KC in MBMD were ∼1.5–5× lower than the errors of conventional MBMD; for cases with complex implants, the errors were ∼3–5× lower. In conclusion, the proposed method can achieve accurate bone mineral density measurements in the presence of metal implants using non-coinciding DE projections acquired on a multisource CBCT system.

Autoimmune retinopathy: findings and limitations from optical coherence tomography angiography

Background and objectiveTo report novel findings and limitations from optical coherence tomography angiography (OCTA) in the evaluation of autoimmune retinopathy (AIR).Study designWe retrospectively reviewed features of five patients diagnosed with AIR and five controls. OCTA scans were obtained and manually segmented to provide accurate measurements of foveal avascular zone (FAZ), vessel density, and retinal thickness at different levels.ResultsThe total retina and superficial vessel density throughout the whole scan were similar between AIR and controls (p = 0.14 and p = 0.11), whereas deep vessel density was decreased in AIR compared controls (p = 0.02). Decreased vessel density was most pronounced in the parafoveal and perifoveal areas (p = 0.01 and p = 0.01). AIR patients also had reduction of total retinal thickness in the perifoveal zone (p = 0.03), corresponding to outer retinal thinning (p = 0.001).ConclusionThis small series shows that AIR patients have reduced deep vessel density, particularly in the parafoveal and perifoveal regions and a decrease in macular thickness. These findings show correlation with the classic “flying saucer” sign seen on OCT.

Single-electromagnet levitation for density measurement and defect detection

This paper presents a single-electromagnet levitation device to measure the densities and detect the internal defects of antimagnetic materials. The experimental device has an electromagnet in its lower part and a pure iron core in the upper part. When the electromagnet is activated, samples can be levitated stably in a paramagnetic solution. Compared with traditional magnetic levitation devices, the single-electromagnet levitation device is adjustable. Different currents, electromagnet shapes, and distances between the electromagnet and iron core are used in the experiment depending on the type of samples. The magnetic field formed by the electromagnet is strong. When the concentration of the MnCl2 aqueous solution is 3 mol/L, the measuring range of the single-electromagnet levitation device ranges from 1.301 to 2.308 g/cm3. However, with the same concentration of MnCl2 aqueous solution (3 mol/L), the measuring range of a magnetic levitation device built with permanent magnets is only from 1.15 to 1.50 g/cm3. The single-electromagnet levitation device has a large measuring range and can realize accurate density measurement and defect detection of high-density materials, such as glass and aluminum alloy.

Development of Ar+16 charge exchange recombination spectroscopy measurements at ASDEX Upgrade

Argon is being considered as a radiator for future fusion devices. To support this, experiments in present day devices are needed to assess its effectiveness as a radiator and to study its compatibility with key aspects of reactor operation. For these purposes, accurate measurement of the Ar density in the confined plasma region are required. Charge exchange recombination spectroscopy is capable of providing this information, but requires validated cross-sections to produce accurate density profiles. For typical ASDEX Upgrade plasma parameters Ar+16 is the charge state of the most interest and the ArXVI n = 15–14 was identified as the best target for these measurements. Due to the fine structure splitting, the Ar charge exchange (CX) emission lines are highly asymmetric and detailed modeling is required to extract accurate ion temperatures or rotations. For the evaluation of Ar+16 densities, there are two main sets of CX cross-sections available: the data calculated by Schultz et al (Whyte et al 2010 J. Phys. B At. Mol. Opt. Phys 43 144002, Schultz et al 2010 J. Phys. B At. Mol. Opt. Phys. 43 144002) (ORNL) and by Errea et al (2006 J. Phys. B At. Mol. Opt. Phys. 39 L91) (UAM). These cross-sections differ by over an order of magnitude and have very different energy dependencies. In this work, the validity of these datasets is tested experimentally. The Ar density profiles calculated using the ORNL cross-sections are 10–50× too large while the UAM densities are a factor of 2.73 too small. The UAM data, however, does a much better job at capturing the observed energy dependence. The authors conclude that the CTMC calculations of Errea, which use a hydrogenic distribution to describe the initial target and donor distributions better reproduce the experimental data. However, to produce accurate Ar density profiles, these cross-sections need to be corrected downward and the best profiles are produced with a small correction to the UAM energy dependence.

Analysis of Age-Based Bone Mineral Density in the Korean Adult Population Using Dual-Energy X-ray Absorptiometry

Dual-energy X-ray absorptiometry (DEXA) provides a reliable and accurate measurement of bone density and bone mineral composition. This research examined the composition and bone density (bone mineral composition and bone mineral density; BMD) of the whole body and selected body parts using DEXA. The participants were 240 healthy adult men and women who were divided into three groups based on age. The total BMD of women amounted to an average of 1.14 g/cm2 for those aged 20–39 years, 1.14 g/cm2 for those aged 40–59 years, and 0.98 g/cm2 for those aged 60–73 years. For men, the average BMD was 1.25 g/cm2 for those aged 20–39 years, 1.20 g/cm2 for those aged 40–59 years, and 1.17 g g/cm2 for those aged 60–73 years. The decrease in age-specific BMD was shown to have a correlation with both age and body mass index, and it is determined that exercising on a regular basis can prevent a reduction in BMD by maintaining appropriate muscle mass.

Study on the thermophysical properties of waste cooking oil biodiesel fuel blends with 1-butanol

An Anton Paar vibrating tube densimeter HPM DMA calibrated with an uncertainty of ±0.7 kg•m−3 has been used for accurate measurements of liquid densities of Waste Cooking Oil Biodiesel (WCOB) and 1-butanol as pure fluids and binary liquid mixtures. The densities measurements were performed at temperatures (298.15 K to 393.15 K) and pressures (0.1 MPa to 140 MPa) and showing an absolute deviation of less than 0.007 g/cm−3 compared to the literature data. Using these new experimental data (908 points), excess molar volumes VE, isobaric thermal expansivity, αp, and isothermal compressibility, кT, have been calculated. The Tait and PC-SAFT equations correlate successfully the densities with a small absolute average deviation (AAD), the PC-SAFT model performs very well in all concentration range with a global absolute average deviation (AAD) of 0.325% and for Tait equation a global absolute average deviation of 0.086% for each concentration. PC-SAFT equation correlates satisfactorily the density and shows that it can explain the same interactions between fluid molecules contrary to the Tait equation. Excess volumes values were calculated from the experimental data and show a positive parabolic shape in all composition range almost symmetrical in the fraction molar 0.5. Furthermore, VE values were fitted to the Redlich-Kister equation and showed satisfactory correlation with very small standard deviation values with a global of 4.23·10−5 cm3·mol−1.

High-speed density measurement for LNG and other cryogenic fluids using electrical capacitance tomography

The global custody transfer market for liquefied natural gas (LNG) has grown at a strong pace in the last decade and use of LNG as transport fuel has considerable environmental benefits. The quantity of LNG is traded on the basis of energy transferred, calculated from volume, density and gross calorific value. High-speed, accurate density measurement is therefore of significant commercial value.The electrical capacitance tomography (ECT) device described in this paper has the potential to measure the LNG density rapidly, on-line at a moderate cost. Continuous monitoring of variation in LNG density during dynamic LNG flow measurement also gives a good indication of change in fluid quality and thus onset of boiling which is known to affect measurement accuracy. ECT is a leading candidate to be explored for online density measurements through measurement of electrical permittivity, as in addition to average value, it offers the image of permittivity across the whole flow conduit, allowing localised bubbles, boiling or other variations to be identified and measured.We report here experiments to explore the use of ECT in cryogenic applications. An 8-electrode test ECT sensor was designed, built and tested in laboratory conditions and then in liquid nitrogen. The resolution and imaging capability in cryogenic conditions are shown to be comparable to that under laboratory conditions. The experiments reported here use liquid nitrogen as an analogue fluid, but the results presented are believed to be representative of many cryogenic fluids. Although the use of ECT has been widely reported in the literature for multiphase flows in general, its use has not previously been reported for cryogenic flows. This paper offers proof of principle for ECT cryogenic multi-phase density and flow measurement.Dielectric constant is strongly linked to fluid density, and the ECT sensor design tested here shows an estimated measurement of the relative permittivity of liquid nitrogen of 1.45 with a standard measurement error of 0.034. Measurement stability at cryogenic conditions gave an rms variation of output under static conditions of better than 0.001 relative permittivity units even though it was unguarded and only a single electrode ring. The primary errors are associated with the unguarded nature of the test sensor, which was primarily designed as a proof of concept and material demonstrator.In addition, such an ECT sensor would provide clear images of any gas in the liquid and give a good estimation of the concentration and velocity of the gas bubbles. The scope of this work is to provide a proof of concept of the cryogenic ECT sensor.

Opportunistic osteoporosis screening: contrast-enhanced dual-layer spectral CT provides accurate measurements of vertebral bone mineral density

ObjectivesOsteoporosis remains under-diagnosed, which may be improved by opportunistic bone mineral density (BMD) measurements on CT. However, correcting for the influence of intravenous iodine-based contrast agent is challenging. The purpose of this study was to assess the diagnostic accuracy of iodine-corrected vertebral BMD measurements derived from non-dedicated contrast-enhanced phantomless dual-layer spectral CT (DLCT) examinations.MethodsVertebral volumetric DLCT-BMD was measured in native, arterial, and portal-venous scans of 132 patients (63 ± 16 years; 32% women) using virtual monoenergetic images (50 and 200 keV). For comparison, conventional BMD was determined using an asynchronous QCT calibration. Additionally, iodine densities were measured in the abdominal aorta (AA), inferior vena cava, and vena portae (VP) on each CT phase to adjust for iodine-related measurement errors in multivariable linear regressions and a generalized estimated equation, and conversion equations were calculated.ResultsBMD values derived from contrast-enhanced phases using conversion equations adjusted for individual vessel iodine concentrations of VP and/or AA showed a high agreement with those from non-enhanced scans in Bland-Altman plots. Mean absolute errors (MAE) of DLCT-BMD were 3.57 mg/ml for the arterial (R2 = 0.989) and 3.69 mg/ml for the portal-venous phase (R2 = 0.987) (conventional BMD: 4.70 [R2 = 0.983] and 5.15 mg/ml [R2 = 0.981]). In the phase-independent analysis, MAE was 4.49 mg/ml for DLCT (R2 = 0.989) (conventional BMD: 4.82 mg/ml [R2 = 0.981]).ConclusionsConverted BMD derived from contrast-enhanced DLCT examinations and adjusted for individual vessel iodine concentrations showed a high agreement with non-enhanced DLCT-BMD, suggesting that opportunistic BMD measurements are feasible even in non-dedicated contrast-enhanced DLCT examinations.Key Points• Accurate BMD values can be converted from contrast-enhanced DLCT scans, independent from the used scan phase.• DLCT-BMD measurements from contrast-enhanced scans should be adjusted with iodine concentrations of portal vein and/or abdominal aorta, which significantly improves the goodness-of-fit of conversion models.