Black-blood MRI is a promising imaging technique for assessing vascular diseases (e.g., stroke). Vessel wall dynamic characterization using black-blood cine MRI has been recognized as an effective tool for studying vascular diseases. However, acquiring time-resolved 3D vessel wall images often requires a long acquisition time, which limits its clinical utility. In this work, we develop a new method to achieve rapid, time-resolved 3D black-blood cine MRI. Specifically, the proposed method performs (k, t)-space undersampling to accelerate the volumetric data acquisition process. Moreover, it utilizes an image reconstruction method with low-rank and sparsity constraints to enable high-quality image reconstruction from highly-undersampled data. We validate the performance of the proposed method with 3D in vivo black-blood cine MRI experiments and show representative results to demonstrate the utility of the proposed method.
Background: Hemolysis and its complications are major concerns during the clinical application of blood pumps. In-vitro circulatory testing loops have been employed as the key procedure to evaluate the hemolytic and thrombogenic performance of blood pumps during the development phase and before preclinical in-vivo animal studies. Except for the blood damage induced by the pump under test, blood damage induced by loop components such as the resistance valve may affect the accuracy, reproducibility, and intercomparability of test results. Methods: This study quantitatively investigated the impact of the resistance valve on in vitro evaluation of blood damage caused by blood pumps under different operating points. A series of idealized tubing models under the resistance valve with different openings were created. Three pumps - the FDA benchmark pump, the HeartMate 3 LVAD, and the CH-VAD - were involved in hypothetical tests. Eight operating points were chosen to cover a relatively wide spectrum of testing scenarios. Computational fluid dynamics (CFD) simulations of the tubing and pump models were conducted at the same operating points. Results and Conclusion: Overall, hemolysis and platelet activation induced by a typical resistance valve are equivalent to 17%-45% and 14%-60%, respectively, of those induced by the pump itself. Both ratios varied greatly with flow rate, valve opening and pump models. Differences in blood damage levels between different blood pumps or working conditions can be attenuated by up to 45%. Thus, hemolysis and platelet activation induced by the resistance valve significantly affect the accuracy of in-vitro hemocompatibility evaluations of blood pumps. A more accurate and credible method for hemocompatibility evaluations of blood pumps will benefit from these findings.
Abstract Background Hypoxic–ischemic encephalopathy (HIE) refers to cerebral hypoxic–ischemic injury caused by asphyxia during perinatal period, which is one of the important causes of neonatal death and sequelae. Early and accurate diagnosis of HIE is of great significance for the prognostic evaluation of patients. The purpose of this study is to explore the efficacy of diffusion-kurtosis imaging (DKI) and diffusion-weighted imaging (DWI) in the diagnosis of early HIE. Methods Twenty Yorkshire newborn piglets (3–5 days) were randomly divided into control group and experimental group. DWI and DKI scanning were performed at timepoints of 3, 6, 9, 12, 16, and 24 h after hypoxic–ischemic exposure. At each timepoint, the parameter values obtained by each group scan were measured, and the lesion area of the apparent diffusion coefficient (ADC) map and mean diffusion coefficient (MDC) map were measured. (For better interpretation of this study, we replaced the description of MD with MDC). Then, we completely removed the brain for pathological examination, and observed the state of cells and mitochondria in the ADC/MDC matching area (the actual area of the lesion), and the mismatch area (the area around the lesion). Results In the experimental group, the ADC and MDC values decreased with time, but the MDC decreased more significantly and the change rate was higher. Both MDC and ADC values changed rapidly from 3 to 12 h and slowly from 12 to 24 h. The MDC and ADC images showed obvious lesions at 3 h for the first time. At this time, the area of ADC lesions was larger than that of MDC. As the lesions developed, the area of ADC maps was always larger than that of the MDC maps within 24 h. By observing the microstructure of the tissues by light microscopy, we found that the ADC and MDC matching area in the experimental group showed swelling of neurons, infiltration of inflammatory cells, and local necrotic lesions. Consistent with the observation under light microscope, pathological changes were observed in the matching ADC and MDC regions under electron microscopy as well, including collapse of mitochondrial membrane, fracture of partial mitochondrial ridge, and emergence of autophagosomes. In the mismatching region, the above pathological changes were not observed in the corresponding region of the ADC map. Conclusions DKI’s characteristic parameter MDC is better than ADC (parameter of DWI) to reflect the real area of the lesion. Therefore, DKI is superior to DWI in diagnosing early HIE.
Blood damage induced by mechanical circulatory support devices (MCSDs) remains a significant challenge to optimal clinical care. Although researchers have been conducting in vitro studies, the major determinant of blood damage is still unclear. An optimized capillary tube blood-shearing platform with custom designed parts was constructed to investigate the influence of two flow-dependent parameters (shear stress and exposure time) on the shear-induced damage of red blood cells and von Willebrand factor (VWF). Blood samples under different high shear stress and instantaneous exposure time were obtained by changing the flow rate and the length of capillary tube. Plasma free hemoglobin assay and immunoblotting of VWF were then performed on the sheared blood samples. The quantitative correlation between the hemolysis index and the two flow-dependent parameters was found following the power law mathematical model under the flow condition with high shear stress and instantaneous exposure time. The degradation of high molecular weight VWF was not obvious under high shear stress factor. However, the degradation of high molecular weight VWF was found as the result of the accumulation over exposure time under non-physiological shear stress, which was consistent with the different mechanism of VWF damage comparing to red blood cell damage. Compared to peak shear stress, exposure time has a greater effect on both red blood cell and VWF damage. To improve the hemocompatibility of MCSDs, it is more important to avoid regions of slow blood flow with non-physiological shear stress under laminar flow conditions.
Bidirectional coupling systems for electricity and natural gas composed of gas units and power-to-gas (P2G) facilities improve the interactions between different energy systems. In this paper, a combined optimization planning method for an electricity-natural gas coupling system with P2G was studied. Firstly, the characteristics of the component model of the electricity-natural gas coupling system were analyzed. The optimization planning model for the electricity-natural gas coupling system was established with the goal of minimizing the sum of the annual investment costs and the annual operation costs. Based on the established model, the construction statuses for different types of units, power lines, and pipelines and the output distribution values for gas units and P2G stations were optimized. Then, the immune algorithm was proposed to solve the optimization planning model. Finally, an electricity-natural gas coupling system composed of a seven-node natural gas system and a nine-node power system was taken as an example to verify the rationality and effectiveness of the model under different scenarios.
Motivation: Bariatric surgery can rapidly alter obese status, but its effects on resting state functional connectivity (rsFC) in obesity remain unclear. Goal(s): We examined the effects of bariatric surgery on rsFC between brain networks in obese patients using independent component analysis. Approach: Thirty obese patients underwent resting state fMRI scans before and after bariatric surgery. We used independent component analysis to analyze surgery-related rsFC changes. Results: Bariatric surgery improved rsFC of hVN-lFPN, hVN-SMN, AUN-pDMN, AUN-DAN, pVN-aDMN, pVN-SMN, pDMN-SN, aDMN-DAN, and SMN-DAN in obese patients. These results indicate that bariatric surgery induces functional reorganization of brain networks in obesity. Impact: Bariatric surgery can rapidly alter obese status. Our study investigates the rsFC before and after bariatric surgery, results show that bariatric surgery induces functional reorganization of brain networks in obesity.
By combining power electronics, innovative induction machine design, and centrifugal pump principles, a distinct design of the shaftless and compact pump device has been proposed. The mathematical model of the proposed device has been derived. Three-dimensional finite element method was applied to analyze the performances and to verify the mathematical model of the device. An experimental test-rig was fabricated. Both the analysis results and the experimental measurements support the feasibility of the system. The advantages of the proposed design, such as being shaftless and having far less risk of leakage or contamination of the fluid to be pumped, make it significant in biomedical and bioengineering applications
Abstract Maglev bearings can avoid serious blood damage caused by mechanical bearings, and has become the primary trend of blood pumps. Maglev blood pumps allow a relatively large clearance to improve blood washout and reduce the stress inside the clearance so that blood damage can be reduced. Nonetheless, large clearances also lead to high secondary flow and turbulence intensity, causing further blood damage. This study aims to conduct a thorough analysis of flow fields in two typical maglev blood pumps, the CH-VAD and Heartmate III which feature distinct designs of secondary flow path and impeller (semi-open versus closed impeller) using large eddy simulation (LES) with a focus on the secondary flows and their interaction with the main flows. LES was found to be superior to the Reynolds-averaged Navier-Stokes (RANS) method in predicting performance curves. At high flow rate (8L/min), the efficiency of CH-VAD remains high compared with 5 L/min, while the efficiency of Heartmate III drops considerably. The wide clearance in Heartmate III induced high secondary flow and flow loss, leading to an large incidence angle at both working conditions. The high viscous stress inside the clearances is the major cause of flow loss and potential blood damage in CH-VAD. This study shows that Maglev bearings dose not guarantee good blood compatibility, clearances should be designed based on trade-offs among high shear stress inside smaller clearance, and strong recirculations caused by larger clearances. This study provides useful reference for the design and optimization of maglev blood pumps.
The aim of this study is to perform patient-specific hemodynamic simulations of patients with iliac vein compression syndrome (IVCS) and evaluate the deep venous thrombosis (DVT) potential, with clinical observations as reference. 15 patient-specific IVCS models were reconstructed from computed tomography venography (CTV) data, and divided into three groups, i.e. two groups with thrombosis: Group A (complete obstruction) and Group B (incomplete obstruction), and a third group without DVT, Group C. Hemodynamic simulations were conducted with patient-specific inlet flow rates. The blood residue was predicted using the blood stasis model. Time histories of old blood volume fraction (OBVF) was obtained, in addition to conventional hemodynamic parameters such as wall shear stress (WSS). The mean area-averaged WSS of the stenosis region for Group A and Group B were 3.68 Pa and 1.78 Pa, respectively. For the telecentric end region, the WSS were 0.76 Pa and 0.58 Pa, respectively. For Group C, the WSS at these two regions were 4.61 Pa and 1.57 Pa, respectively. The OBVF was 74.0% at the stenosis region and 76.2% at the telecentric end region for Group A, much higher than 4.8% and 43.1% of Group B. For Group C, the OBVF at the two regions were close to 0. This corresponded well with clinical observations. The potential of DVT can be predicted through patient-specific hemodynamic simulations in combination of blood stasis model. The findings of this study are of great significance for the preoperative evaluation and treatment prognosis of IVCS patients with DVT.
'/%3e%3cuse xlink:href='%23a' transform='rotate(23.036 .093 25.536)'/%3e%3cuse xlink:href='%23a' transform='rotate(45.87 1.273 16.18)'/%3e%3cuse xlink:href='%23a' transform='rotate(69.945 .996 12.078)'/%3e%3cuse xlink:href='%23a' transform='rotate(20.66 -19.689 31.932)'/%3e%3c/svg%3e)