Volume Flow Measurements Research Articles

Good agreement between cardiac magnetic imaging protocols using free-breathing and breath-holding techniques for flow quantification in valvular heart disease

Abstract Background Cardiac magnetic resonance (CMR) evaluation of valvular heart disease is an important diagnostic tool when echocardiography is inconclusive. Flow quantification is usually performed during breath hold, which can be challenging in valvular heart disease patients often suffering from dyspnea and heart failure. Purpose The purpose of the present study is to evaluate a free-breathing protocol of flow measurement in the aortic, pulmonary and tricuspid valves in healthy subjects (HS) and patients with tricuspid regurgitation (TR). Methods Phase contrast flow volume measurements were performed in 20 HS and 25 patients with TR using standard breath-holding (BH) and a free-breathing (FB) technique. Two venc-adjusted volume acquisition were acquired in the aortic, pulmonary and tricuspid valve during BH and one during FB. Mean, standard deviation (SD) and limits of agreement (LoA) for aortic forward flow volume (AoFF), pulmonary forward flow volume (PuFF) and tricuspid inflow volume (TrIF) were evaluated. Results Figure 1 presents flow volume (ml) of AoFF, PuFF and TrIF during BH (mean of 2 measurements) and FB. Conclusions The present study demonstrated good agreements between phase contrast flow measurements using FB and BH techniques. These parameters are used in the evaluation of aortic, mitral, pulmonary and tricuspid regurgitations using CMR imaging. Thus, free-breathing CMR acquisition can be an important complement in the assessment of valvular heart disease and may be applied in patients with difficulty to hold their breath.

The relationship between post-anastomosis brachial artery flow rate and brachiocephalic arteriovenous fistula access maturity in end-stage kidney disease patients with diabetes mellitus

Background: From previous studies, evaluation of post-anastomosis draining-vein volume flow rate with Doppler ultrasound can be a predictor for arteriovenous fistula maturation. Due to the high variation in measurements by the effect of probe pressure in draining vein, measuring volume flow rate based on post-anastomosis feeding-artery may be an early alternative predictor of arteriovenous fistula maturation. This study aims to investigate the correlation of post-creation brachial artery volume flow rate on maturity of brachiocephalic arteriovenous fistula access in patients with end-stage kidney disease with diabetes mellitus. Methods: A retrospective cohort study was conducted on end-stage kidney disease patients with diabetes mellitus who underwent brachiocephalic arteriovenous fistula creation at three hospitals from July 2019 to March 2020. Doppler ultrasound examination of the brachial artery and draining vein volume flow rate was conducted at pre-operative, post-creation, 2 weeks, and 6 weeks post-creation. Maturity was evaluated at 6 weeks post-anastomosis. Results: A total of 71 subjects met the inclusion and exclusion criteria, with 44 (62%) achieving maturation within 6 weeks. There was a correlation between post-anastomosis brachial artery (p < 0.001) and draining vein volume flow rate (p < 0.001) with arteriovenous fistula maturity after 6 weeks post-operatively. Brachial artery volume flow rate of ⩾350 mL/min can predict AVF maturity with a sensitivity of 95.45% (95% confidence interval = 84.86–98.74) and a specificity of 85.19% (95% confidence interval = 67.52–94.08). Conclusion: Post-anastomosis brachial artery flow volume can be a valuable parameter to predict brachiocephalic arteriovenous fistula maturity. It is a potential alternative to draining vein volume flow, which is technically a difficult examination.

Normal menstrual flow volume range and its characteristics measured from sanitary napkins in Japanese women: Discrepancy between measured and subjective menstrual flow volume.

The 2018 International Federation of Gynecology and Obstetrics abnormal uterine bleeding System-1 defines menstrual flow volume on a 3-point scale based on subjective assessment. However, the normal flow range has not been established, and it is unclear whether subjective assessment is accurate. We investigated the normal menstrual flow volume range in Japanese women and whether the actual measured menstrual flow volume agreed with the subjective evaluation. We included female menstruating volunteers aged 18-49 years in this prospective observational study. Menstrual napkins were weighed before and after use for up to three cycles, and the values were recorded in an online diary. Overall, 211 participants were recruited. All items were completed by 167 participants, and 497 menstrual cycles were included in the analysis. The median total menstrual flow volume per cycle for 497 cycles was 56.7 g. The 5th-95th percentile values ranged from 15.7 to 166.4 g. The mean value was 77.6 ± 99.6 g, with no significant differences according to age group. In the 25 cycles corresponding to heavy flow, that is, above the 95th percentile of measured flow volume, 92% were underrated as "normal" by subjective evaluation, and only 8% were correctly rated as "heavy." Our results clarify the actual menstrual flow volume in the Japanese population; this will contribute toward making women aware of the normal range of menstrual flow volume, which may facilitate appropriate preconception care.

The Role of Platelets and Aneurysm Thrombus in the EVAR Post Implantation Syndrome

ObjectivePost implantation syndrome (PIS) is a well-defined entity with unclear etiology, complicating a number of patients with AAAs treated with EVAR. The aim of this study was to assess the platelets’ role and the influence of aneurysmal sac thrombus volumes in the development of PIS. DesignA retrospective analysis of prospectively collected data was performed and 76 patients that were treated by EVAR (2011-2013) were studied. Aneurysms with endoleak were not included in the study. Based on the criteria for SIRS (Systemic Inflammatory Response Syndrome), 17 patients (22%) developed PIS (which is considered a SIRS analogue), while 59 (78%) did not. MethodsThe two groups were compared in relation to the following parameters: baseline platelet count (PLT), decrease of platelet count (PLT drop), volume of the arterial flow before the procedure (V Flow), volume of thrombus of the aneurysm (V thromb), ratio of thrombus volume to aneurysm sac volume (V ratio) and the volume of new formed thrombus (V new). Volume flow measurements were calculated by Osirix ™ software preoperatively and in the 1st month postoperatively. Parametric and non-parametric techniques (unpaired t-test, Mann-Whitney U test) were used accordingly. ResultsBaseline platelets absolute count was greater in the PIS group (239000 ± 17000) vs. the non-PIS group (194000 ± 6900, p=0.004), and the PLT drop was larger in the PIS group (74000 ± 15600 vs. 45000 ± 5300, p=0.019). No difference was found regarding the aneurysm volumes (Vflow, Vthromb, Vratio, Vnew) between the two groups. ConclusionPlatelets, in terms of their absolute baseline count and their decrease after the procedure, seem to be an important factor in developing PIS after EVAR. Further, more tailored studies are needed to elucidate the role of platelets and flow/thrombus volumes in the development of PIS.

Experimental and numerical characterization of screw elements used in twin-screw extrusion

Hot melt extrusion by a co-rotating twin screw extruder is an important process in the pharmaceutical industry. Especially for quality by design aspects, a comprehensive process understanding is indispensable. The performance of conveying elements was determined as critical process parameter, and therefore an experimental and numerical framework was developed to analyze and compare variations. A test rig capable of measuring volume flow, pressure and torque with high accuracy and precision was designed and built. The 3D simulation was performed using computational fluid dynamics (CFD). A stationary model with impulse transmission and an apparent motion of the screws was applied. The experimental data were fitted to the model of Pawlowski, and parameters for the pressure (A1, A2) and power characteristics (B1, B2) were determined. Good agreement between experimental data and the model was observed. The simulation was significantly faster compared to common methods, and the results were consistent with the literature. Systematic investigations of a native and worn screw were performed with CFD resulting in a transport capacity increase and a pressure build up decrease for all tested screw elements. An experimental and simulation setup was generated to assess the performance of co-rotating twin screw elements. The experiments provided high-quality data, and the simulations exhibited high flexibility with low computational effort.

Assessment of alternative fluid calibration to estimate traceable liquefied hydrogen flow measurement uncertainty

The usage of liquefied hydrogen (LH2) is growing fast as the EU aims to be climate-neutral by 2050. Therefore, reliable and consistent measurements of LH2 amounts (as determined by flow meters) will become increasingly important for custody transfers. Reliability and consistency of measurements is established from calibration. Due to the lack of facilities being able to calibrate flow meters directly with LH2 as calibration fluid, the question arises whether the measurement error of the calibration performed on a different fluid and different process conditions are representative for the errors when measuring LH2. An on-site calibration of two turbine meters measuring LH2 flow was performed. A Coriolis mass flow meter calibrated on water was used as a reference in conjunction with a dedicated flow meter model, which was validated by a directly SI-traceable calibration on liquefied natural gas. LH2 flow rates were within 1000 kg/h and 3000 kg/h, which are relevant to hydrogen transport by LH2 trailers. The analysis of the measurement data reveal errors on totalized mass ranging from 2.0 % to 2.9 % with a total calibration uncertainty of 1.3 % (k=2), where the main uncertainty source was identified as the on-site density estimate necessary to convert the volume flow measurements into mass flow measurements. The results indicate the need for reliable and accurate temperature measurements (the latter allowing for an accurate density estimate), so that volume based and mass based amount measurements can be compared with smaller uncertainties.

Differentiation Between High-Grade Glioma and Brain Metastasis Using Cerebral Perfusion-Related Parameters (Cerebral Blood Volume and Cerebral Blood Flow): A Systematic Review and Meta-Analysis of Perfusion-weighted MRI Techniques.

Distinguishing high-grade gliomas (HGGs) from brain metastases (BMs) using perfusion-weighted imaging (PWI) remains challenging. PWI offers quantitative measurements of cerebral blood flow (CBF) and cerebral blood volume (CBV), but optimal PWI parameters for differentiation are unclear. To compare CBF and CBV derived from PWIs in HGGs and BMs, and to identify the most effective PWI parameters and techniques for differentiation. Systematic review and meta-analysis. Twenty-four studies compared CBF and CBV between HGGs (n = 704) and BMs (n = 488). Arterial spin labeling (ASL), dynamic susceptibility contrast (DSC), dynamic contrast-enhanced (DCE), and dynamic susceptibility contrast-enhanced (DSCE) sequences at 1.5 T and 3.0 T. Following the PRISMA guidelines, four major databases were searched from 2000 to 2024 for studies evaluating CBF or CBV using PWI in HGGs and BMs. Standardized mean difference (SMD) with 95% CIs was used. Risk of bias (ROB) and publication bias were assessed, and I2 statistic was used to assess statistical heterogeneity. A P-value<0.05 was considered significant. HGGs showed a significant modest increase in CBF (SMD = 0.37, 95% CI: 0.05-0.69) and CBV (SMD = 0.26, 95% CI: 0.01-0.51) compared with BMs. Subgroup analysis based on region, sequence, ROB, and field strength for CBF (HGGs: 375 and BMs: 222) and CBV (HGGs: 493 and BMs: 378) values were conducted. ASL showed a considerable moderate increase (50% overlapping CI) in CBF for HGGs compared with BMs. However, no significant difference was found between ASL and DSC (P = 0.08). ASL-derived CBF may be more useful than DSC-derived CBF in differentiating HGGs from BMs. This suggests that ASL may be used as an alternative to DSC when contrast medium is contraindicated or when intravenous injection is not feasible. Stage 2.

Assessment of volume flow rate in arteriovenous fistulas with a novel ultrasound Doppler device (earlybird): Trend analysis, comparison of methods, and inter- and intra-rater reliability.

An accessible tool is required to analyze volume flow trends in arteriovenous fistulas for hemodialysis. Earlybird, an easy-to-place ultrasound Doppler device, has shown comparable accuracy to duplex ultrasound. In this study, we compared volume flow measurements obtained with duplex ultrasound and the dilution technique to an enhanced earlybird device, featuring a dual Doppler probe system, eliminating the requirement for a known insonation angle. Nine patients with a distal radiocephalic arteriovenous fistula were monitored for 12 months with regular volume flow measurements. Correlation and inter- and intra-class reliability analyses were conducted. An overall moderate correlation was observed between earlybird and duplex ultrasound or dilution technique (intraclass correlation coefficient = 0.606 (95% confidence interval 0.064, 0.721) and 0.581 (0.039, 0.739), respectively). Duplex ultrasound compared to dilution measurements, demonstrated an overall moderate correlation (0.725 (0.219, 0.843)). Correlation between earlybird and duplex ultrasound was stronger for the arteriovenous fistula (0.778 (0.016, 0.901)) than the brachial artery (0.381 (-0.062, 0.461)). For earlybird, inter-rater reliability was excellent for the arteriovenous fistula (0.907 (0.423, 0.930)) and poor for the brachial artery (0.430 (0.241, 0.716)). Duplex ultrasound showed a good inter-rater reliability (arteriovenous fistula: 0.843 (0.610, 0.871), brachial artery: 0.819 (0.477, 0.864)). The overall intra-rater reliability was good for duplex ultrasound (rater A: 0.893 (0.727, 0.911); rater B: 0.853 (0.710, 0.891)), while excellent for earlybird (rater A: 0.905 (0.819, 0.928); rater B: 0.921 (0.632, 0.969)). We observed a weaker correlation in the measurements of volume flow rates in arteriovenous fistulas when obtained using earlybird compared to dilution technique, unlike the comparison between duplex ultrasound and the dilution technique. However, inter-rater reliability for the arteriovenous fistula was excellent with earlybird and good with duplex ultrasound, indicating the potential of earlybird as a tool for frequent measurements, enabling trend surveillance and predicting adverse outcomes.

Maternal use of snus as smokeless tobacco in pregnancy and infant lung function.

Smoking in pregnancy has detrimental effects on infant respiratory health, while the effects of other nicotine-containing products on infant lung function are unclear. We aimed to explore if smokeless tobacco such as snus used in pregnancy increased the risk of lower lung function in infancy and if the associations differed by sex. From the Scandinavian population-based Preventing Atopic Dermatitis and ALLergies in Children birth cohort, we included 1163 infants with available tidal flow-volume measurements at 3 months of age and maternal self-reported use of nicotine-containing products in pregnancy. The risk of a ratio of time to peak tidal expiratory flow to total expiratory time <25th percentile by any nicotine exposure, snus exclusively and cigarette smoking with or without other nicotine-containing products was explored by regression analyses adjusting for maternal age, education and asthma. Overall 120 out of 1163 (10.3%) infants were exposed to any nicotine in utero, 71 out of 120 by snus exclusively and 49 out of 120 by smoking, with six also exposed to snus. By pregnancy week 6, 85.8% of mothers reported stopping nicotine use. The risk of lower lung function was higher in children exposed in utero to nicotine-containing products with an odds ratio (OR) of 1.63 (95% confidence interval (CI) 1.02-2.59) with a similar tendency for snus exclusively (OR 1.55, 95% CI 0.88-2.71) and smoking (OR 1.79, 0.84-3.84). Effect estimates were similar after adjusting for covariates. No differences of the effect by sex were observed. Our study suggests that in utero exposure to not only cigarettes, but also snus, may negatively affect infant lung function.

Spirometry test values can be estimated from a single chest radiograph.

Physical measurements of expiratory flow volume and speed can be obtained using spirometry. These measurements have been used for the diagnosis and risk assessment of chronic obstructive pulmonary disease and play a crucial role in delivering early care. However, spirometry is not performed frequently in routine clinical practice, thereby hindering the early detection of pulmonary function impairment. Chest radiographs (CXRs), though acquired frequently, are not used to measure pulmonary functional information. This study aimed to evaluate whether spirometry parameters can be estimated accurately from single frontal CXR without image findings using deep learning. Forced vital capacity (FVC), forced expiratory volume in 1 s (FEV1), and FEV1/FVC as spirometry measurements as well as the corresponding chest radiographs of 11,837 participants were used in this study. The data were randomly allocated to the training, validation, and evaluation datasets at an 8:1:1 ratio. A deep learning network was pretrained using ImageNet. The input and output information were CXRs and spirometry test values, respectively. The training and evaluation of the deep learning network were performed separately for each parameter. The mean absolute error rate (MAPE) and Pearson's correlation coefficient (r) were used as the evaluation indices. The MAPEs between the spirometry measurements and AI estimates for FVC, FEV1 and FEV1/FVC were 7.59% (r = 0.910), 9.06% (r = 0.879) and 5.21% (r = 0.522), respectively. A strong positive correlation was observed between the measured and predicted indices of FVC and FEV1. The average accuracy of >90% was obtained in each estimation of spirometry indices. Bland-Altman analysis revealed good agreement between the estimated and measured values for FVC and FEV1. Frontal CXRs contain information related to pulmonary function, and AI estimation performed using frontal CXRs without image findings could accurately estimate spirometry values. The network proposed for estimating pulmonary function in this study could serve as a recommendation for performing spirometry or as an alternative method, suggesting its utility.

Does central venous stenosis affects the brachial artery flow volume and peripheral vascular resistive index in patients on maintenance hemodialysis? A retrospective study.

A well-functioning vascular access (VA) is crucial for the patients on maintenance hemodialysis (HD). Central venous stenosis (CVS) is a common, yet, overlooked complication of VA as its diagnosis is challenging. Moreover, its effect on the flow volume (FV) and the peripheral resistive index (RI) was not well discussed before. Despite the availability of doppler ultrasound (DUS) in most centers, direct visualization of central veins using DUS is quite difficult. This is a retrospective single-center self-controlled cohort study that was conducted in a specialized vascular access management tertiary center in Japan and included all patients with CVS who underwent percutaneous transluminal angiography (PTA) with or without vascular stenting in the period from January 2014 to September 2022. The patients were divided according to their VA type into arteriovenous fistula (AVF), and arteriovenous graft (AVG) groups, then subdivided, according to the type of stenosis, into two subgroups: CVS, and mixed central and peripheral venous stenosis (MVS) groups. The FV and RI of the feeding artery were compared in the same procedure before and after PTA to assess the impact of the procedure itself. Data of 485 percutaneous transluminal angiography procedures (PTA), performed in 95 patients during the period from January 2014 to September 2022, were collected. FV and RI were significantly affected in the patients with MVS than patients with CVS. After PTA, both FV and RI were significantly improved. The improvement rate of FV and RI after PTA were significantly higher in patients with MVS than patients with CVS. However, it was difficult to determine the cut-off value to diagnose or to assess the improvement of CVS. Our findings suggest that FV and RI measurement by DUS are good tools, along with the clinical findings for assessment of CVS in certain situations.

MEASUREMENT OF TRANSPORTED GAS CONSUMPTION: ANALYSIS OF MEASUREMENT METHODS

One of the key aspects in the development of the economy of the Republic of Azerbaijan is the export of natural gas to foreign countries. The relevance of the issue of measuring consumption increases over time with the expansion of gasification operations in the country and the growth of gas exports to the international market. Therefore, there is a demand for the development of new projects for the improvement of the used metering systems in accordance with modern standards, their reconstruction with more efficient methods, and the discovery and application of new measuring devices and methods. During such reconstruction activities, the main focus is naturally on creating optimal and cost-effective information measurement systems. The measurement process is a precision-demanding operation, and various nuances affect the reliability of the result. Metrology is the scientific discipline that implements measurement processes. The key stage for its accuracy is the proper organization of the measurement device and methods in accordance with the characteristics of these devices. Additionally, the expertise of the personnel involved in the measurement process significantly influences the reliability of the measurement result. Failure to adhere to these processes negatively impacts the reliability of the result. In Azerbaijan, the widely used method of consumption measurement is the orifice metering method (ISO 5167-1), but this method has both advantages and disadvantages for large-diameter flow meters. These include a limited range of measured flow velocities, fouling and contamination of the diaphragm edge during operation, the complexity and high labor intensity of regular technical maintenance, high costs of spare parts, and the construction and installation of measuring devices. These problems lead to inaccuracies in gas consumption measurement, causing time and material losses during the process. Improving the accuracy of gas measurement in Azerbaijan can significantly increase financial gains. Therefore, alongside traditional methods, there is an interest in developing new methods for measuring volume flow with high accuracy and user convenience, as well as lower initial and operating costs. One of the promising areas for the development of modern flow measurement technology is the use of optoelectronics. Among them, the most significant interest lies in the use of Laser Doppler interferometry methods. These methods have been proven to be the most effective for studying physically dispersed environments (such as gas and liquid). The advantages of Laser Doppler anemometry, based on these methods, such as high accuracy and speed, a wide measurement range, resistance to noise, the possibility of simulated calibration, controllability of characteristics, and non-changeability according to the surrounding environment, make them highly favorable. The high accuracy of flow meters based on Laser Doppler anemometry allows them to be used both as working tools and as metrological support means for the verification of flow meters. Keywords: Gas consumption measurement, Measurement systems, Measurement methods, Orifice metering method, Laser Doppler.

Combined free-running four-dimensional anatomical and flow magnetic resonance imaging with native contrast using Synchronization of Neighboring Acquisitions by Physiological Signals

Four-dimensional (4D) flow magnetic resonance imaging (MRI) often relies on the injection of gadolinium- or iron-oxide-based contrast agents to improve vessel delineation. In this work, a novel technique is developed to acquire and reconstruct 4D flow data with excellent dynamic visualization of blood vessels but without the need for contrast injection. Synchronization of Neighboring Acquisitions by Physiological Signals (SyNAPS) uses pilot tone (PT) navigation to retrospectively synchronize the reconstruction of two free-running three-dimensional radial acquisitions, to create co-registered anatomy and flow images. Thirteen volunteers and two Marfan syndrome patients were scanned without contrast agent using one free-running fast interrupted steady-state (FISS) sequence and one free-running phase-contrast MRI (PC-MRI) sequence. PT signals spanning the two sequences were recorded for retrospective respiratory motion correction and cardiac binning. The magnitude and phase images reconstructed, respectively, from FISS and PC-MRI, were synchronized to create SyNAPS 4D flow datasets. Conventional two-dimensional (2D) flow data were acquired for reference in ascending (AAo) and descending aorta (DAo). The blood-to-myocardium contrast ratio, dynamic vessel area, net volume, and peak flow were used to compare SyNAPS 4D flow with Native 4D flow (without FISS information) and 2D flow. A score of 0-4 was given to each dataset by two blinded experts regarding the feasibility of performing vessel delineation. Blood-to-myocardium contrast ratio for SyNAPS 4D flow magnitude images (1.5±0.3) was significantly higher than for Native 4D flow (0.7±0.1, p<0.01) and was comparable to 2D flow (2.3±0.9, p=0.02). Image quality scores of SyNAPS 4D flow from the experts (M.P.: 1.9±0.3, E.T.: 2.5±0.5) were overall significantly higher than the scores from Native 4D flow (M.P.: 1.6±0.6, p=0.03, E.T.: 0.8±0.4, p<0.01) but still significantly lower than the scores from the reference 2D flow datasets (M.P.: 2.8±0.4, p<0.01, E.T.: 3.5±0.7, p<0.01). The Pearson correlation coefficient between the dynamic vessel area measured on SyNAPS 4D flow and that from 2D flow was 0.69±0.24 for the AAo and 0.83±0.10 for the DAo, whereas the Pearson correlation between Native 4D flow and 2D flow measurements was 0.12±0.48 for the AAo and 0.08±0.39 for the DAo. Linear correlations between SyNAPS 4D flow and 2D flow measurements of net volume (r2 =0.83) and peak flow (r2 =0.87) were larger than the correlations between Native 4D flow and 2D flow measurements of net volume (r2 =0.79) and peak flow (r2 =0.76). The feasibility and utility of SyNAPS were demonstrated for joint whole-heart anatomical and flow MRI without requiring electrocardiography gating, respiratory navigators, or contrast agents. Using SyNAPS, a high-contrast anatomical imaging sequence can be used to improve 4D flow measurements that often suffer from poor delineation of vessel boundaries in the absence of contrast agents.

Improving the efficiency of the maintenance and monitoring system for mine degassing pipelines

Degassing pipelines in mine workings frequently change position, causing leaks and joint failures due to geomechanical processes and floor rock heaving, which lead to fatigue and corrosion. This paper reviews maintenance and renovation methods for these pipelines, aiming to develop innovative solutions to enhance operational performance. Research focuses on assessing current maintenance techniques, improving reliability, and implementing new technical solutions under real mine conditions. The proposed technological complex aims to enhance the safety and quality of pipeline maintenance and renovation. Typical production scenarios and monitoring methods for effective control of the technical state of mine degassing systems are considered. Continuous control of degassing wells and pipelines using structural modules of the Automated Mine Degassing Control System (AMDCS) is emphasized. Implementing these modules allows for automatic monitoring of the methane-air mixture and measurement of pressure drops, absolute pressure, temperature, and gas flow volume, thereby providing critical data to operational personnel.

Color Doppler ultrasound evaluation of arteriovenous grafts for hemodialysis.

Although arteriovenous fistula (AVF) continues to be the vascular access of choice for the hemodialysis, arteriovenous graft (AVG) can be the best choice in certain categories of patients and could have several advantages over AVF in a "patient centered approach" to vascular access. In the clinical management of prosthetic fistulas, color Doppler ultrasound (CDU) is the imaging method of choice for identifying stenosis and other AVG complications. In this review, besides highlighting the pivotal role of CDU in the diagnosis of AVG complications, we will underline the key role that ultrasound can play in identifying those stenosis most likely to cause AVG thrombosis. Furthermore, we will emphasize the support that CDU can play in distinguishing the different types of grafts and prosthetic devices such as stent-grafts, in identifying AVG with lower survival, CDU utilities and limitations in the evaluation of freshly-implanted grafts, the different sites available for AVG volume flow measurement and their use based on the configuration of the prosthesis, the time interval elapsed from the surgical intervention and the integrity of the prosthetic walls.

Comparing direct and indirect glottal flow waveform measurements in excised canine larynges and synthetic vocal fold models

Despite being considered the gold standard technique for delineating the flow glottogram during phonation, the inverse filtering technique has never been validated against actual volume flow measurements. This signal-processingtechnique uses the speech signal with vocal tract estimates to calculate the glottal flow waveform. The lack of validation stems from the difficulty of obtaining in-vivo flow measurements at the glottal exit. The current study aims to assess the accuracy of the inverse filtering technique by comparing its flow glottograms with direct, simultaneous volume flow measurement. A vocal tract with varied constrictions that mimic its shape according to specific vowels was connected to either an excised canine larynx or a synthetic vocal fold model. Direct volume flow measurements at the glottal exit were done using tomographic particle image velocimetry. Indirect measurements were obtained by fitting the known Rothenberg mask to the vocal tract and estimating the glottal flow waveform using the Glottal Enterprise system. Preliminary results indicate that the accuracy of the inverse filtering technique relies on the degree of vocal tract constriction. The flow glottogram aligns well with front, lax, and unrounded lip vowels, but its accuracy diminishes with tense and round vowels, particularly noticeable with the excised canine larynx.

Application of real time shear wave elastography to the differential diagnosis of secondary parathyroid hyperplasia and adenoma.

We aimed to explore the value of ultrasonic elastic imaging in the diagnosis of parathyroid hyperplasia and adenoma in patients with secondary hyperparathyroidism and provide more evidence for clinical treatment. Forty patients who were on dialysis and underwent parathyroid surgery were selected All patients underwent routine ultrasound, ultrasound elasticity examination and blood biochemical examination before surgery, including calcium, phosphorus, parathyroid hormone (PTH), etc. According to postoperative results, adenoma group and hyperplasia group were divided into 2 groups. Receiver operating characteristic curve was drawn to evaluate the diagnostic efficacy and combined diagnostic efficacy of each index. The PTH levels significantly differed between the adenoma and hyperplasia groups (P < .001). The volume and blood flow grades significantly differed between the adenoma and hyperplasia groups (P < .001) The minimum of the adenoma group was 14.62 ± 6.79 kPa, mean was 19.42 ± 6.29 kPa, and maximum was 24.25 ± 6.35 kPa which were significantly different from those in the hyperplasia group (P < .05). The combinations of more than 6 indicators in the diagnosis of parathyroid adenoma resulted in an area under the curve of 0.892 (P < .001), and the sensitivity and specificity were 78.9% and 97.4%, respectively. Shear wave elastography can be used as an effective tool to distinguish secondary parathyroid hyperplasia from adenoma. When combined with PTH, conventional ultrasound blood flow grading and volume measurement, it has higher diagnostic efficacy.

Application of Simple Crested Weirs to Control Outflows from Tiles Drainage

Triangular sharp-crested weirs are commonly used to measure low-flow measurements in open channels. The flow over such a V-notch is proportional to the height of water above the weir on the upstream side. Therefore, it is relatively easy to calculate the flow from standard equations by using only recordings of water levels. Thus, these types of weirs can provide inexpensive measurements of flow volumes and resulting nutrient loads from subsurface drainage systems and associated conservation practices. The objective of this study was to develop appropriate weir equations for a 22.5° V-notch weir developed for a new tubular water level control structure in a controlled drainage system (CD). Analyses using this weir, with three typical slope angles of 30°, 45°, and 60°, were also conducted. There were no significant differences in the fitted parameters across the three analyzed slope angles. The coefficient of determination (R2) values were 0.9955, 0.9981, and 0.9980, respectively. However, the best-fitted equation for a 22.5° V-notch weir was for a slope angle of 45°. The flow equation was Q = 0.2235H2.4182, with Q in liters per minute and H in centimeters. This equation can be used for measuring flow through tubular-controlled drainage structures.

Low-Power AlGaN/GaN Triangular Microcantilever for Air Flow Detection.

This paper investigates an AlGaN/GaN triangular microcantilever with a heated apex for airflow detection utilizing a very simple two-terminal sensor configuration. Thermal microscope images were used to verify that the apex region of the microcantilever reached significantly higher temperatures than other parts under applied voltage bias. The sensor response was found to vary linearly with airflow rate when tested over a range of airflow varying from 16 to 2000 sccm. The noise-limited flow volume measurement yielded ~4 sccm resolution, while the velocity resolution was found to be 0.241 cm/s, which is one of the best reported so far for thermal sensors. The sensor was able to operate at a very low power consumption level of ~5 mW, which is one of the lowest reported for these types of sensors. The intrinsic response time of the sensor was estimated to be on the order of a few ms, limited by its thermal properties. Overall, the microcantilever sensor, with its simple geometry and measurement configurations, was found to exhibit attractive performance metrics useful for various sensing applications.

Deep learning phase error correction for cerebrovascular 4D flow MRI

Background phase errors in 4D Flow MRI may negatively impact blood flow quantification. In this study, we assessed their impact on cerebrovascular flow volume measurements, evaluated the benefit of manual image-based correction, and assessed the potential of a convolutional neural network (CNN), a form of deep learning, to directly infer the correction vector field. With IRB waiver of informed consent, we retrospectively identified 96 MRI exams from 48 patients who underwent cerebrovascular 4D Flow MRI from October 2015 to 2020. Flow measurements of the anterior, posterior, and venous circulation were performed to assess inflow-outflow error and the benefit of manual image-based phase error correction. A CNN was then trained to directly infer the phase-error correction field, without segmentation, from 4D Flow volumes to automate correction, reserving from 23 exams for testing. Statistical analyses included Spearman correlation, Bland–Altman, Wilcoxon-signed rank (WSR) and F-tests. Prior to correction, there was strong correlation between inflow and outflow (ρ = 0.833–0.947) measurements with the largest discrepancy in the venous circulation. Manual phase error correction improved inflow-outflow correlation (ρ = 0.945–0.981) and decreased variance (p < 0.001, F-test). Fully automated CNN correction was non-inferior to manual correction with no significant differences in correlation (ρ = 0.971 vs ρ = 0.982) or bias (p = 0.82, Wilcoxon-Signed Rank test) of inflow and outflow measurements. Residual background phase error can impair inflow-outflow consistency of cerebrovascular flow volume measurements. A CNN can be used to directly infer the phase-error vector field to fully automate phase error correction.