Recovery Coefficient Research Articles

Characterization of the partial volume effect along the axial field-of-view of the Biograph Vision Quadra total-body PET/CT system for multiple isotopes

BackgroundTotal-body PET scanners with axial field of views (FOVs) longer than 1 m enable new applications to study multiple organs (e.g., the brain-gut-axis) simultaneously. As the spatial resolution and the associated partial volume effect (PVE) can vary significantly along the FOV, detailed knowledge of the contrast recovery coefficients (CRCs) is a prerequisite for image analysis and interpretation of quantitative results. The aim of this study was to determine the CRCs, as well as voxel noise, for multiple isotopes throughout the 1.06 m axial FOV of the Biograph Vision Quadra PET/CT system (Siemens Healthineers).Materials and MethodsCylindrical phantoms equipped with three different sphere sizes (inner diameters 7.86 mm, 28 and 37 mm) were utilized for the PVE evaluation. The 7.86 mm sphere was filled with F-18 (8:1 and 4:1), Ga-68 (8:1) and Zr-89 (8:1). The 28 mm and 37 mm spheres were filled with F-18 (8:1). Background concentration in the respective phantoms was of ~ 3 kBq/ml. The phantoms were measured at multiple positions in the FOV (axial: 0, 10, 20, 30, 40 and 50 cm, transaxial: 0, 10, 20 cm). The data were reconstructed with the standard clinical protocol, including PSF correction and TOF information with up to 10 iterations for maximum ring differences (MRDs) of 85 and 322; CRCs, as well as voxel noise levels, were determined for each position.ResultsF-18 CRCs (SBR 8:1 and 4:1) of the 7.86 mm sphere decreased up to 18% from the center FOV (cFOV) toward the transaxial edge and increased up to 17% toward the axial edge. Noise levels were below 15% for the default clinical reconstruction parameters. The larger spheres exhibited a similar pattern. Zr-89 revealed ~ 10% lower CRCs than F-18 but larger noise (9.1% (F-18), 19.1% (Zr-89); iteration 4, cFOV) for the default reconstruction. Zr-89 noise levels in the cFOV significantly decreased (~ 28%) when reconstructing the data with MRD322 compared with MRD85 along with a slight decrease in CRC values. Ga-68 exhibited the lowest CRCs for the three isotopes and noise characteristics comparable to those of F-18.ConclusionsDistinct differences in the PVE within the FOV were detected for clinically relevant isotopes F-18, Ga-68 and Zr-89, as well as for different sphere sizes. Depending on the positions inside the FOV, the sphere-to-background ratios, count statistics and isotope used, this can result in an up to 50% difference between CRCs. Hence, these changes in PVE can significantly affect the quantitative analysis of patient data. MRD322 resulted in slightly lower CRC values, especially in the center FOV, whereas the voxel noise significantly decreased compared with MRD85.

Rapid Whole-Body FDG PET/MRI in Oncology Patients: Utility of Combining Bayesian Penalised Likelihood PET Reconstruction and Abbreviated MRI.

This study evaluated the diagnostic value of a rapid whole-body fluorodeoxyglucose (FDG) positron emission tomography (PET)/magnetic resonance imaging (MRI) approach, combining Bayesian penalised likelihood (BPL) PET with an optimised β value and abbreviated MRI (abb-MRI). The study compares the diagnostic performance of this approach with the standard PET/MRI that utilises ordered subsets expectation maximisation (OSEM) PET and standard MRI (std-MRI). The optimal β value was determined by evaluating the noise-equivalent count (NEC) phantom, background variability, contrast recovery, recovery coefficient, and visual scores (VS) for OSEM and BPL with β100-1000 at 2.5-, 1.5-, and 1.0-min scans, respectively. Clinical evaluations were conducted for NECpatient, NECdensity, liver signal-to-noise ratio (SNR), lesion maximum standardised uptake value, lesion signal-to-background ratio, lesion SNR, and VS in 49 patients. The diagnostic performance of BPL/abb-MRI was retrospectively assessed for lesion detection and differentiation in 156 patients using VS. The optimal β values were β600 for a 1.5-min scan and β700 for a 1.0-min scan. BPL/abb-MRI at these β values was equivalent to OSEM/std-MRI for a 2.5-min scan. By combining BPL with optimal β and abb-MRI, rapid whole-body PET/MRI could be achieved in ≤1.5 min per bed position, while maintaining comparable diagnostic performance to standard PET/MRI.

Discrete elemental parameter calibration of stacking behavior of sugarcane tail leaf sieved material

To improve the accuracy of discrete element simulation parameters of sugarcane tail-leaf (STL) feed during dust removal and crushing, this study used a combination of physical tests and EDEM software simulations to calibrate the discrete element simulation parameters of crumbs and dust in the feed. Taking the experimental physical stacking angle (SA) as the response value, the second-order regression models of SA and significant factors were established by Plackett-Burman test, steepest climb test, and Box-Behnken test. Variance analysis and interaction effect analysis were conducted. Taking the accumulation angle of 41.27° obtained by physical experiments as the target value, the significant parameters were optimized. The optimal combination of the following parameters was obtained: tail stem-dust static friction coefficient (SFC) of 0.46, tail leaf-dust coefficient of sliding friction (COSF) of 0.205, JKR surface energy of 0.26, and dust-steel collision recovery coefficient (CRC) of 0.338. Through software simulation verification, the average value was 40.81°, and the relative error of the SA with the physical experiment was 1.13%. The results showed that the calibrated parameters are real and reliable, which can provide a theoretical reference for the design optimization of the straw crushing device, feed processing device, and other related components.

Study on heat transfer characteristics of air-cooled dry bottom ash removal system

This paper develops a numerical model to describe the bottom ash cooling process based on an actual power plant. By means of computational fluid dynamics, the influence of adjusting the operating parameters of the dry bottom ash removal system was investigated. The heat exchange enhancement effect and the resulting consequences were comprehensively considered. After comparing its results with the measured values, the model is considered valid. The numerical results indicate that: increasing air volume is an effective method to reduce ash discharge temperature but not desirable; the ash discharge temperature decreased from 452.47 K to 446.27 K, but the air outlet temperature also decreased by 6.05 K. Increasing the running speed of the conveyor belt is an ideal measure; the heat recovery coefficient improves by 7.53% as the speed increases from 0.046 m/s to 0.0766 m/s. In addition, a dry bottom ash removal system with a specific structure has rated ash handling capacity; its design should fully consider the amount of bottom ash discharge. Adjusting the operating mode may not significantly reduce the ash discharge temperature without other losses. The results provide a reference for designing and adjusting subsequent bottom ash sensible heat utilization equipment.

Study of the influence of non-carbon gases on the condensate recovery coefficient of gas condensate fields using a hydrodynamic model

There is enough research work on the effective use of non-hydrocarbon gases in order to increase the component recovery of hydrocarbon deposits. Over a long period, we have also carried out a number of research works on the effect of nitrogen and carbon dioxide on the final condensate recovery factor of fields, as well as on the productivity of gas condensate wells. However, it is known that the formation systems of gas condensate fields, along with other non-hydrocarbon gases, contain nitrogen and carbon dioxide. Sometimes their number has a rather large share in the total volume. But, the effect of the amount of nitrogen and carbon dioxide naturally present in reservoir systems on the final condensate recovery coefficient of gas condensate fields has not been studied enough. The influence of the amount of nitrogen and carbon dioxide in the composition of reservoir systems on the condensate recovery coefficient of gas condensate fields has been studied. To this end, a multicomponent hydrodynamic model of the Bulla-Sea field was used as a base case, the factors influencing the process were studied by comparing the final condensate recovery coefficient of the field with other systems containing nitrogen and carbon dioxide.

Numerical Investigation of Aerodynamic and Electromagnetic Performances for S-Duct Caret Intake with Boundary-Layer Bleed System

This study presents the numerical results for the aerodynamic and electromagnetic performances of an S-duct caret intake. Using the multilevel fast multipole method (MLFMM) to solve Maxwell equations, the current on the intake surface is calculated, and the radar cross-section (RCS) is analyzed. Moreover, the intake flow field is numerically investigated using the SST k–ω turbulence model to solve the Reynolds-averaged Navier–Stokes equations. Compared to a straight intake, for an S-duct caret intake, the average RCS is lower by 7.65 dB, and the maximum RCS difference value caused by the blade rotation is lower by 6.75 dB. However, the flow capacity deteriorates when the total pressure recovery coefficient decreases by 0.004. Based on the analysis of the aerodynamic and electromagnetic characteristics of different intakes, a double S-duct intake is designed. Compared to a traditional S-duct intake, for the novel intake after model parameter modification, the average RCS is lower by 0.05 dB, and the total pressure distortion (TPD) is lower by 0.18. The analysis of the effects of different boundary-layer bleed systems shows that the symmetrical layout adversely affects the aerodynamic and electromagnetic performances of the S-duct intake, but the unilateral partial layout is beneficial, whose TPD is lower by 0.04 and average RCS is higher by −2.17 dB compared to a straight intake.

Comparison of the detectability of hot lesions on bone SPECT using six state-of-the-art SPECT/CT systems: a multicenter phantom study to optimize reconstruction parameters.

Single-photon emission computed tomography with X-ray computed tomography (SPECT/CT) systems have diversified due to the remarkable developments made by each manufacturer. This study aimed to optimize the reconstruction parameters of six state-of-the-art SPECT/CT systems and compare their image quality of bone SPECT.SPECT images were acquired on SPECT/CT systems, including Symbia Intevo, Discovery NM/CT 670, Discovery NM/CT 870 CZT, Brightview XCT, and VERITON-CT. SIM2 bone phantom with tough lung phantoms on both sides of the spinal inserts that simulate the thorax was used for image quality assessment. SPECT images were obtained at individual workstations using an ordered subset expectation maximization method with three-dimensional resolution recovery, as well as CT attenuation and scatter correction, subset 2, iteration 12-84, and a full width at half maximum 10-mm Gaussian smooth filter. An automatic image analysis software dedicated to SIM2 bone phantom was used to assess the contrast-to-noise ratio (CNR), relative recovery coefficient, percentage of coefficient of variance, contrast, and detectability. The optimal parameters for each system were defined with superior detectability of spherical lesions and noise characteristics, as well as the highest CNR.All systems exhibited better image quality indexes using the optimal parameters than using the manufacturer's recommended parameters. The detectability of all systems was in agreement while using the optimal parameters.Detectability agreement can be achieved by optimizing the reconstruction parameters for different reconstruction algorithms, which can further improve the image quality. Therefore, future research should focus on optimal reconstruction parameters for SPECT alone.

Experimental Analysis and Verification of the Influence on the Elastic Recovery Coefficient of Wheat

To establish a collision model of wheat grains impacting a force plate with a piezoelectric sensor, and to investigate the influence of the elastic recovery coefficient on the sensor’s detection accuracy during the collision process, this study employed object kinematic principles to construct a wheat elastic recovery coefficient measurement device. This device ascertains the elastic properties of wheat during collisions and determines the elastic recovery coefficient of the wheat collision model. The wheat variety Jinan No. 17 was selected for testing, and the effects of the contact material, grain drop height, material thickness, and grain moisture content on the collision recovery coefficient during the collision process were analyzed through single-factor and multi-factor experiments. The experimental results demonstrate that the collision recovery coefficient of wheat grains increases with the stiffness of the collision materials for different materials. The grain recovery coefficient of wheat exhibits a downward trend with increasing falling height and moisture content, while it tends to rise as the material thickness increases. Data analysis and comparison reveal that, given the determination of the collision material, the moisture content of wheat exerts the most significant effect on the elastic recovery coefficient, followed by material thickness, while the influence of falling height is less pronounced. The findings of this study can provide data support for simulation testing and product design of wheat combine harvester cleaning screen body mechanisms and wheat seeders.

Experimental and Numerical Studies of the Aerodynamics of Stationary Two-Shaft Gas Turbine Exhaust System

In this study, the aerodynamic performance of the exhaust system of a two-shaft gas turbine was investigated experimentally and numerically. The investigation focused on the system “Turbine Stage-Diffuser—Collector Box” and aimed to examine the impact of inlet conditions and geometry particularities on the efficiency of the exhaust system. The experiments were conducted on the Test Ring ET4 (Experimental Turbine-4) at the Peter the Great St.Petersburg Polytechnic University, which was equipped with a special diversion channel to examine the non-axisymmetric outlet of the exhaust duct. The collector box was designed to rotate by 180 degrees around the turbine axis to investigate its impact on the system’s performance. Flow traversing parameters were measured with the five-channel pneumatic pressure probes, and numerical simulations were performed with CFX 15.0. The RANS (Reynolds-averaged Navier–Stokes) equations were closed with the SST (k-ω) turbulence model (Shear Stress Transport model). The study concluded that the RANS SST model predicts the flow in the diffuser before the struts accurately. However, downstream the struts, the CFD (Computer fluid dynamic) results over-predicted the exhaust diffuser pressure recovery coefficient by 14% due to the complex vortex structure of the turbulent flow, which the Averaged Navier–Stokes equations did not resolve. The study highlights the importance of considering the last stage of the turbine, diffuser, and collector box as an integrated system when investigating the aerodynamics of exhaust ducts. The study also emphasizes the impact of geometry and inlet conditions on the exhaust diffuser’s performance and efficiency. The results of this study can be used to optimize the design of the exhaust system of two-shaft gas turbines and improve their thermal efficiency. The integrated approach of combining experimental and numerical methods can provide a detailed and reliable flow picture and can be used for future research in this area.

Numerical Simulation and Wind Tunnel Test of a Variable Geometry Auxiliary Inlet for a Wide-Body Aircraft Environmental Control System

A variable geometry auxiliary inlet for a wide-body aircraft environmental control system with moveable deflectors operating in a large mass flow rate range is studied through numerical simulation and wind tunnel tests, which yields a design method for the variable geometry auxiliary inlet with high performance. The characteristics of the flow field are studied by numerical simulation. The results show that the favorable pressure gradient and the roll-up vortices are the major impetus that inhales the incoming flow into the inlet. The law of regulation and the performance variation under different conditions are obtained by wind tunnel test. The flow coefficient increases first but then decreases with the increase in the inlet opening, and the pressure rise ratio and total pressure recovery coefficient increase first and then decrease with the increase in the mass flow rate. In general, under the condition of a high Mach number (Ma > 0.4), the inlet opening of this test configuration should not exceed 50%. The deflectors can maintain the normal work of the environmental control system by moving properly to control the mass flow rate of the auxiliary inlet.

Influences of microjet pressure and number of microjets on the control of shock wave/boundary layer interaction

Boundary layer separation is a common phenomenon in supersonic/hypersonic vehicles, and can adversely affect the lift coefficient. Currently, active flow control based on microjets is used to inhibit the separation of the turbulent boundary layer. The obtained results predicted by the three-dimensional Reynolds-averaged Navier–Stokes (RANS) equations and two-equation shear stress transport (SST) k-ω both with Realizable k-ε turbulence models show that the control mechanism of the microjets method is the counter-rotating vortex pair (CVP) generated by the microjet mixes the low-energy flow within the boundary layer with the high-energy flow near the boundary layer. The size of the vortex core in this CVP is the key to controlling SWBLI. The vortex nucleus that is larger and closer to the wall enables better SWBLI control. A lower or higher ratio of microjet pressure to inflow static pressure increases the total volume of the separation bubble and produces a negative gain. When the ratio of the triangular microjet hole bottom edge length to the spacing between the holes is too small, leading to a deterioration in the control effect. The addition of microjets reduces the total pressure recovery coefficient.

Design and examination of a turboprop inlet with scavenge duct

The inlet with scavenge duct is an important part of turboprop aircraft engine. This type of inlet normally has a complex shape, of which the design is challenging and directly affects the flow field quality of the engine entrance and thus the engine performance. In this paper, the parametric design method of a turboprop aircraft inlet with scavenge duct is established by extracting and controlling the transition law of the critical characteristic parameters. The inlet’s performance and internal flow characteristics are examined by wind-tunnel experiment and numerical simulation. The results indicate that a flow tendency of winding up on both sides is formed due to the induction of the inlet profile, as well as a vortex pair on the back side of the power output shaft. The vortex pair dominates the pressure distortion index on the Aerodynamic Interface Plane (AIP). In addition, with the increase of freestream angle of attack, the total-pressure recovery coefficient of the inlet increases gradually while the total pressure distortion index decreases slightly. On the basis of the experimental results under different working conditions, the parametric design method proposed in this paper is feasible.

ABOUT THE POSSIBILITY OF IMPLEMENTING WATER-ALTERNATING-GAS INJECTION USING PUMP-JET SYSTEMS AT THE ARYSTAN FIELD

At the moment, in the Caspian oil and gas region, many fields are in the final stage of development according to the basic version (flooding). According to it, the final oil recovery coefficient often does not reach the design values. Therefore, for such fields, it is necessary to consider the possibility of using various tertiary methods to increase oil recovery.

Droplet bouncing on moving superhydrophobic groove surfaces

This study examined the bounce behavior of droplets impacting a moving superhydrophobic groove surface (SGS) and focused on the effect of the normal and tangential Weber numbers (Wen and Wes, respectively). The experimental results indicate that the rebound behavior of the droplets varied greatly with the substrate velocity at the same Wen. Furthermore, with an increase in the superhydrophobic substrate velocity, the maximum spreading diameter increased, whereas the dimensionless contact time first increased, then decreased, and finally stabilized. Additionally, scaling laws for predicting the maximum spreading diameter and velocity recovery coefficients were proposed and verified using our experimental data.

Validation of ^{99m}Tc and ^{177}Lu quantification parameters for a Monte Carlo modelled gamma camera

PurposeMonte Carlo (MC) simulation in Nuclear Medicine is a powerful tool for modeling many physical phenomena which are difficult to track or measure directly. MC simulation in SPECT/CT imaging is particularly suitable for optimizing the quantification of activity in a patient, and, consequently, the absorbed dose to each organ. To do so, validating MC results with real data acquired with gamma camera is mandatory. The aim of this study was the validation of the calibration factor (CF) and the recovery coefficient (RC) obtained with SIMIND Monte Carlo code for modeling a Siemens Symbia Intevo Excel SPECT-CT gamma camera to ensure optimal ^{99m}Tc and ^{177}Lu SPECT quantification.MethodsPhantom experiments using ^{99m}Tc and ^{177}Lu have been performed to measure spatial resolution and sensitivity, as well as to evaluate the CF and RC from acquired data. The geometries used for 2D planar imaging were (1) Petri dish and (2) capillary source while for 3D volumetric imaging were (3) a uniform filled cylinder phantom and (4) a Jaszczack phantom with spheres of different volumes. The experimental results have been compared with the results obtained from Monte Carlo simulations performed in the same geometries.ResultsComparison shows good accordance between simulated and experimental data. The measured planar spatial resolution was 8.3pm 0.8 mm for ^{99m}Tc and 11.8±0.6 mm for ^{177}Lu. The corresponding data obtained by SIMIND for ^{99m}Tc was 7.8±0.1 mm, while for ^{177}Lu was 12.4±0.4 mm. The CF was 110.1±5.5 cps/MBq for Technetium and 18.3±1.0 cps/MBq for Lutetium. The corresponding CF obtained by SIMIND for ^{99m}Tc was 107.3±0.3 cps/MBq, while for ^{177}Lu 20.4±0.7 cps/MBq. Moreover, a complete curve RCs vs Volume (ml) both for Technetium and Lutetium was determined to correct the PVE for all volumes of clinical interest. In none of the cases, a RC coefficient equal to 100 was found.ConclusionsThe validation of quantification parameters shows that SIMIND can be used for simulating both gamma camera planar and SPECT images of Siemens Symbia Intevo using ^{99m}Tc and ^{177}Lu radionuclides for different medical purposes and treatments.

Calibrating contact parameters of typical rotary tillage components cutting soil based on different simulation methods

This report analyzes the problem of complex soil movement patterns under the action of coupled forces, such as tension and shear, in agricultural processes and aims to improve the accuracy of contact parameters used in discrete element simulation studies of rototiller-soil interactions. This study focuses on the soil of Shihezi cotton field in the 8th division of Xinjiang and investigates the rotating tiller roller as a soil-touching component of tillage machinery. A combination of simulations and physical testing is used. We perform angle of repose tests and use edge detection, fitting, and other image processing methods to automatically, quickly, and accurately detect the soil accumulation and angle calibration of the contact parameters with soil particles. Additionally, soil slip tests are conducted to calibrate the contact parameters between the soil and the rotary blades. Optimization is achieved based on orthogonal simulations and the Box-Behnken response surface method using physically measured values as the target. A regression model of the stacking angle and rolling friction angle is established to determine the optimal combination of simulation contact parameters: between soil and soil, the recovery coefficient is 0.402, static friction coefficient is 0.621, and rolling friction coefficient is 0.078; between soil contact parts and soil, the recovery coefficient is 0.508, static friction coefficient is 0.401, and rolling friction coefficient is 0.2. Furthermore, the calibration parameters are selected as contact parameters for the discrete element simulation. By combining the above two simulation methods to analyze and compare the simulation process of cutting soil from rototiller roller parts to rototiller single blade parts, we obtained the changes in energy, cutting resistance, and soil particle movement at different depths of the soil cutting process. Finally, the average cutting resistance was used as an index for validation in the field tests. The measured value is 0.96 kN and the error of the discrete element simulation is 13%. This demonstrates the validity of the calibrated contact parameters and the accuracy of the simulation, which can provide a theoretical reference and technical support for the study of the interaction mechanisms between of tillage equipment parts and soil, as well as the design and optimization of these interactions in the future.

Improvement of CNR in low-count PET scans using tissue-scattered data as initial estimate in non-TOF MLEM reconstruction

We have proposed a method to improve contrast-to-noise ratios (CNRs) of lesions in low-count PET scans using the rejected single scattered (inside tissue) data. Indeed, with the advent of high-quality detectors regarding their energy and time resolution, and list mode data acquisition, adding single scattered events by estimating their original line of response has become more and more feasible. The low-count PET scan data were simulated using GATE software considering Jaszczak type object, and images were reconstructed using STIR. A deconvolution based method to create images from rejected single scatter data has been proposed. These scatter images were, in turn, used as an initial estimate in non-TOF MLEM reconstruction. Three types of human-sized PET scanners—ideal, state-of-art, and future generation—with different timing and energy resolutions were considered. We found a significant improvement in trade-off between the contrast recovery coefficient (CRC) and coefficient of variation (CoV) for the non-TOF MLEM reconstructed images while comparing with other less computational ways of creating initial estimates. CNR improvements were found for all lesions. The present work demonstrated the beneficial use of tissue-scattered TOF PET events which constitutes a high percentage of data in PET imaging, and rejected in general. Our approach has a potential and scope for further study.

Multicenter quantitative 18F-fluorodeoxyglucose positron emission tomography performance harmonization: use of hottest voxels towards more robust quantification.

Harmonization methods reduce variability between different make and models of positron emission tomography (PET) scanners. The study aims to explore harmonization strategies that lead to comparable and robust quantitative metrics in a multicenter setting. NEMA IEC Phantom data acquisition was performed for low and high spheres-to-background ratios (SBR4:1 and 10:1) on six PET/CT (computed tomography) scanners. Different reconstruction sets, including the number of sub-iterations, number of subsets, and full width at half maximum (FWHM) for each scanner, were evaluated towards optimized and harmonized reconstruction settings. Recovery coefficients (RCs) of four quantitative metrics, including standardized uptake value (SUV)max, SUVISO-50 (SUVmean in 50% isocontour), SUVpeak, and mean uptake of 10 highest concentration voxels were evaluated as RCmax, RCISO-50, RCpeak, and RC10V, representing percent difference relative to the static ground truth case as functions of sphere sizes. A set of image reconstruction parameters was proposed for harmonized reconstruction to minimize variability between scanners. The root mean square error (RMSE), curvature, and reproducibility were examined. The proposed reconstruction protocols for harmonization and standard clinical reconstruction settings were compared to each other across all scanners. A significant difference (P value <0.0001) was observed in the aforementioned quantitative metrics between SBR10 and SBR4. Reconstruction parameter sets with the smallest RMSE and RC values within 10% bias were identified as the best candidate for harmonization. The coefficient of variation of the mean value of RCs (CVMRC) shows a remarkable reduction of about 28%, 26%, 32%, and 19% in harmonized reconstruction settings for MRCmax, MRCISO-50, MRCpeak, and MRC10V, respectively. CVMRC for MRC10V in the harmonized reconstruction setting was 5.9% in SBR4, while the smallest value in SBR10 belongs to MRCpeak, with a value of 5.8%. The reproducibility of RC is improved by deriving the value from ten hottest voxels and is equally reproducible with RCpeak. Compared to RCmax and RCISO-50, the variability is reduced by 18% and 22% if ten voxels are pooled. Harmonizing PET/CT systems with and without point spread function/time of flight (PSF/TOF) using various vendor-developed image reconstruction algorithms improves the quantification reproducibility. RC10V, likewise RCpeak, is superior to the rest of the quantitative indices in terms of accuracy and reproducibility and helpful in quantifying lesion volume below 1 mL.

Imaging Capabilities of the IRIS and IRIS XL-260 PET/CT Systems for High-Throughput Imaging: A Quantification Cross-Validation Study

The concept of imaging several subjects simultaneously is an active preclinical research topic. In the present paper, we assessed the imaging capabilities of two PET/CT systems based on similar detector technology. The IRIS system is a mice/rat imaging system arranged in two rings of eight detectors each, the more recent IRIS XL 260, dedicated to Non-Human Primate (NHP) imaging has a single ring of sixteen detectors. Both systems were equipped with standard animal cells (Minerve) and 3-mice adapters. Our objective is to study which of these systems could be more appropriate to perform quantitative high-throughput imaging on mice. Phantoms and 18FFDG tumor-bearing mice acquisitions have been conducted in single and high-throughput modes using both the IRIS (up to 3 mice) and the IRIS XL-260 PET/CT (up to 6 mice) systems. Image Quality Phantom results obtained in high-throughput mode show some slight degradation of the recovery coefficient for rods of 1, 2 and 3 mm in diameter compared to the single-mode results, as one would normally expect. Similarly, we observed a decrease in image uniformity between the single-and the high-throughput modes for both the IRIS PET and the IRIS XL-260 PET systems. We performed 18FFDG tumor-bearing mice PET acquisitions with both systems. In order to estimate the quantification differences in all the studied configurations, we calculate the ratios between the %ID/g values extracted from the PET images and the ex-vivo values. In single mode acquisitions, ratios of 0.94 ± 0.09 and 0.83 ± 0.08 were obtained for the IRIS and the IRIS XL-260 PET systems, respectively. In high-throughput mode, ratios of 0.78 ± 0.12 and 0.73 ± 0.13 were obtained for the IRIS and the IRIS XL-260 PET systems, respectively. The difference in %ID/g between static acquisitions and ex-vivo value is not statistically significant (p-value > 0.1) for both PET systems in single mode, as well as for the IRIS system in high-throughput mode. We noted a slightly higher statistical difference between static acquisitions and ex-vivo values for the IRIS XL-260 system with a p-value of 0.015. Phantoms and in-vivo studies have made it possible to highlight the capability of the two systems to perform high-throughput acquisitions. Our results suggest that the IRIS system configuration may be the most suitable when aiming for quantitative high-throughput mice imaging. The large transverse field of view of the IRIS XL-260 makes it possible to image a greater number of mice simultaneously, which may be useful in specific cases, such as studies using an expensive radiotracer and/or with a short half-life. However, the IRIS PET/CT offers a full axial coverage of the animals and a higher sensitivity.

Optimization design of dual microjets for the shock wave/boundary layer interaction control in the supersonic flow

The shock wave/boundary layer interaction phenomenon is harmful to the performance improvement of the hypersonic vehicle, and the microjet flow control scheme was introduced to minimize the total volume of the separation bubble and maximize the total pressure recovery coefficient simultaneously. In this paper, the dual microjets for the shock wave/boundary layer interaction control are optimized by the range analysis approach, and their flow field structures are explored and compared comprehensively. The obtained results show that the range analysis approach is a method for the optimization of the dual microjets, and the optimized models show better performances when compared with the basic configurations. In the range considered in this study, Case 5a obtained by taking the minimum total volume of the separation bubble as the target has a large total pressure loss, and its total volume of the separation bubble is 960.65 mm2, with its total pressure loss being 15.38%.