Eulerian Algorithms for Computing the Forward Finite Time Lyapunov Exponent Without Finite Difference upon the Flow Map

In this paper, effective Eulerian algorithms are introduced for the computation of the forward finite time Lyapunov exponent (FTLE) of smooth flow fields. The advantages of the proposed algorithms mainly manifest in two aspects. First, previous Eulerian approaches for computing the FTLE field are improved so that the Jacobian of the flow map can be obtained by directly solving a corresponding system of partial differential equations, rather than by implementing certain finite difference upon the flow map, which can significantly improve the accuracy of the numerical solution especially near the FTLE ridges. Second, in the proposed algorithms, all computations are done on the fly, that is, all required partial differential equations are solved forward in time, which is practically more natural. The new algorithms still maintain the optimal computational complexity as well as the second order accuracy. Numerical examples demonstrate the effectiveness of the proposed algorithms.     

Nontarget Radiopaque Embolic Deposition during Prostatic Artery Embolization

This study evaluated detectable nontarget embolization (NTE) during prostatic artery embolization (PAE) and the safety and efficacy of using radiopaque particles in PAE. Ten patients aged >40 years with prostate glands of >50 mL and refractory lower urinary tract symptoms were analyzed. Unenhanced computed tomography scans at baseline and at 3 months after PAE, using 40–90-μm radiopaque spherical embolic beads, were compared to assess the NTE. Growth models evaluated changes from baseline to 3, 6, and 12 months in International Prostate Symptom Score (IPSS), peak urine flow rate (Qmax), quality of life (QoL), International Index of Erectile Function (IIEF), and postvoid residual (PVR). The IPSS, QoL, and Qmax improved at all time points (P < .05), with no trend in PVR or IIEF. Adverse events that occurred were minor. Radiographic NTE was seen in all patients, correlating at times with postprocedural symptoms (eg, rectal pain). Symptoms were not correlated with the NTE in some patients, whereas other patients remained asymptomatic despite NTE.     

A Quantitative Comparison of Physical Accuracy and Numerical Stability of Lattice Boltzmann Color Gradient and Pseudopotential Multicomponent Models for Microfluidic Applications

The performances of the Color-Gradient (CG) and the Shan-Chen (SC) multicomponent Lattice Boltzmann models are quantitatively compared side-by-side on multiple physical flow problems where breakup, coalescence and contraction of fluid ligaments are important. The flow problems are relevant to microfluidic applications, jetting of microdroplets as seen in inkjet printing, as well as emulsion dynamics. A significantly wider range of parameters is shown to be accessible for CG in terms of density-ratio, viscosity-ratio and surface tension values. Numerical stability for a high density ratio $\mathcal{O}(1000)$ is required for simulating the drop formation process during inkjet printing which we show here to be achievable using the CG model but not using the SC model. Our results show that the CG model is a suitable choice for challenging simulations of droplet formation, due to a combination of both numerical stability and physical accuracy. We also present a novel approach to incorporate repulsion forces between interfaces for CG, with possible applications to the study of stabilized emulsions. Specifically, we show that the CG model can produce similar results to a known multirange potentials extension of the SC model for modelling a disjoining pressure, opening up its use for the study of dense stabilized emulsions.     

Balancing Workload in the PACU by Using an Integrated OR Planning Methodology

PurposeThe individual scheduling of the operating rooms (ORs) has a significant influence on postoperative care at hospital facilities. We studied the effect of incorporating postoperative departments in the decision process with regard to scheduling ORs and developed an integrated OR planning methodology that determines an optimal surgery sequence and postanesthesia care unit (PACU) nursing staff level, with the objective to level the variability in inflow of patients in the PACU.DesignWe developed an integrated OR planning methodology that investigates the sequencing of a surgical suite process with multiple ORs and postoperative hospital facilities.MethodsThis research was performed by representing a discrete-time two-stage flow shop problem. A retrospective study was performed in which the derived model was validated using discrete-event simulation.FindingsSimulation results show that applying the integrated planning methodology decreased the variability in bed demand and smoothed the workload for the nursing staff in the PACU. Moreover, applying the algorithm led to a decrease in PACU completion time and a reduced amount of overtime hours for the surgical suite. Based on our results, we derived simple scheduling guidelines.ConclusionsOur simulation results confirmed the hypothesis that prospectively sequencing ORs' cases can effectively decrease the variability in bed demand and smoothen the workload for the staff personnel. Moreover, applying the algorithm leads to a decrease in PACU completion time and less overtime hours for the surgical suite. As such, an integrated OR planning methodology facilitates hospitals in improving OR efficiency.     

功能性心肌血流指数评价缺血性冠心病可行性分析

目的:运用功能性心肌血流指数(MBFI)评价缺血性冠心病(ICAD)可行性分析。方法:回顾性分析冠心病疑似患者行冠状动脉CT血管成像(CCTA)检查,同期接受有创冠状动脉造影(ICA)及导管法心肌血流储备分数(FFR)检查共81例患者,其中男性43例,女性38例,年龄(59.27±9.09)岁;计算MBFI;以FFR≤0.80为金标准,分别以四格表诊断试验确定MBFI与ICA的最佳切点值来判断ICAD;评价MBFI、ICA的ROC曲线特征及诊断准确度。结果:81例患者,CCTA扫描平均剂量为(3.06±1.22)mSv。MBFI、ICA最佳切点值分别为0.074、70%,25例患者FFR≤0.80。MBFI、ICA两者ROC曲线下面积分别为0.825、0.699(Z=2.024,P=0.0429),其敏感度、特异度、阳性预测值、阴性预测值分别为88.00%、80.35%、66.67%、93.75%和76.00%、51.79%、41.30%、82.86%,诊断准确度分别为82.72%、59.26%(χ2=10.753,P<0.01)。33例患者(40.74%,33/81)ICA狭窄程度为65%或70%,其中27例患者(81.82%,27/33)心肌不缺血,运用MBFI值大于0.074可明确23例患者心肌并不缺血(69.70%,23/33)。结论:MBFI属于功能性指标,可用于排查缺血性冠心病。     

冠状动脉临界病变血管内超声检查参数与定量血流分数的相关性研究

目的探讨冠状动脉临界病变血管内超声(IVUS)检查参数与定量血流分数(QFR)的相关性。方法前瞻性连续入选2018年9月至2019年9月于同济大学附属东方医院接受QFR和IVUS检查的116例患者(117处冠状动脉临界病变)。根据QFR评估结果,将患者分为QFR≤0.80组(25处病变)和QFR>0.80组(92处病变),比较两组IVUS检查参数的差异。应用Poisson线性相关性分析以及受试者工作特征(ROC)曲线评估IVUS与QFR的相关性,应用logistic多元回归分析QFR≤0.80的预测因素。结果IVUS检查发现,QFR≤0.80组最小管腔面积(MLA)[(3.1±0.8)mm²比(3.6±1.1)mm²,P=0.040]、最小管腔直径(MLD)[(1.8±0.3)mm比(2.0±0.3)mm,P=0.012]显著小于QFR>0.80组,而斑块负荷[(73.5±5.6)%比(68.0±8.4)%,P=0.002]、面积狭窄率[(69.8±8.8)%比(63.8±9.8)%,P=0.007]、斑块偏心指数[(0.83±0.12)比(0.73±0.19),P=0.008]及回声消减斑块比例(52.0%比23.9%,P=0.003)显著高于QFR>0.80组,差异均有统计学意义。Poisson线性相关分析显示,MLA(r=0.259,P=0.005)、MLD(r=0.300,P=0.001)与QFR正相关,而斑块负荷(r=–0.357,P<0.001)以及斑块偏心指数(r=–0.247,P=0.008)与QFR负相关。logistic多因素回归分析表明斑块负荷>70%(OR 4.531,95%CI 1.443~14.222,P=0.010)和斑块偏心指数(OR 1.066,95%CI 1.014~1.121,P=0.012)为QFR≤0.80的独立预测因素。结论冠状动脉临界病变IVUS检查结果中斑块负荷>70%以及斑块偏心指数是QFR≤0.80的独立预测因子。