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A new method for scaling inlet flow waveform in hemodynamic analysis of aortic dissection 主动脉夹层血流动力学分析中缩放入口血流波形的新方法。
IF 2.2 4区 医学 Q3 ENGINEERING, BIOMEDICAL Pub Date : 2024-07-25 DOI: 10.1002/cnm.3855
Kaihong Wang, Chlöe H. Armour, Baolei Guo, Zhihui Dong, Xiao Yun Xu

Computational fluid dynamics (CFD) simulations have shown great potentials in cardiovascular disease diagnosis and postoperative assessment. Patient-specific and well-tuned boundary conditions are key to obtaining accurate and reliable hemodynamic results. However, CFD simulations are usually performed under non-patient-specific flow conditions due to the absence of in vivo flow and pressure measurements. This study proposes a new method to overcome this challenge by tuning inlet boundary conditions using data extracted from electrocardiogram (ECG). Five patient-specific geometric models of type B aortic dissection were reconstructed from computed tomography (CT) images. Other available data included stoke volume (SV), ECG, and 4D-flow magnetic resonance imaging (MRI). ECG waveforms were processed to extract patient-specific systole to diastole ratio (SDR). Inlet boundary conditions were defined based on a generic aortic flow waveform tuned using (1) SV only, and (2) with ECG and SV (ECG + SV). 4D-flow MRI derived inlet boundary conditions were also used in patient-specific simulations to provide the gold standard for comparison and validation. Simulations using inlet flow waveform tuned with ECG + SV not only successfully reproduced flow distributions in the descending aorta but also provided accurate prediction of time-averaged wall shear stress (TAWSS) in the primary entry tear (PET) and abdominal regions, as well as maximum pressure difference, ∆Pmax, from the aortic root to the distal false lumen. Compared with simulations with inlet waveform tuned with SV alone, using ECG + SV in the tuning method significantly reduced the error in false lumen ejection fraction at the PET (from 149.1% to 6.2%), reduced errors in TAWSS at the PET (from 54.1% to 5.7%) and in the abdominal region (from 61.3% to 11.1%), and improved ∆Pmax prediction (from 283.1% to 18.8%) However, neither of these inlet waveforms could be used for accurate prediction of TAWSS in the ascending aorta. This study demonstrates the importance of SDR in tailoring inlet flow waveforms for patient-specific hemodynamic simulations. A well-tuned flow waveform is essential for ensuring that the simulation results are patient-specific, thereby enhancing the confidence and fidelity of computational tools in future clinical applications.

计算流体动力学(CFD)模拟在心血管疾病诊断和术后评估方面显示出巨大潜力。要获得准确可靠的血液动力学结果,关键在于针对特定患者的、经过良好调整的边界条件。然而,由于缺乏体内流量和压力测量,CFD 模拟通常是在非患者特异性流动条件下进行的。本研究提出了一种新方法,利用从心电图(ECG)中提取的数据调整入口边界条件,从而克服这一挑战。研究人员根据计算机断层扫描(CT)图像重建了五个特定于患者的 B 型主动脉夹层几何模型。其他可用数据包括梗塞容积 (SV)、心电图和 4D 流磁共振成像 (MRI)。对心电图波形进行处理,以提取患者特定的收缩与舒张比率(SDR)。入口边界条件是根据使用(1)SV 和(2)ECG 和 SV(ECG + SV)调整的通用主动脉血流波形定义的。4D 流磁共振成像得出的入口边界条件也用于特定患者的模拟,以提供比较和验证的黄金标准。使用经 ECG + SV 调整的入口流波形进行模拟,不仅成功再现了降主动脉中的血流分布,还准确预测了主入口撕裂(PET)和腹部区域的时间平均壁剪应力(TAWSS),以及主动脉根部到远端假腔的最大压力差 ∆Pmax。与仅使用 SV 调整入口波形的模拟相比,在调整方法中使用 ECG + SV 可显著降低 PET 处假腔射血分数的误差(从 149.1% 降至 6.2%),降低 PET 处 TAWSS 的误差(从 54.1% 降至 5.7%)和腹部区域的 TAWSS 误差(从 61.3% 降至 11.1%),并改善了 ∆Pmax 预测(从 283.1% 降至 18.8%)。然而,这两种入口波形都不能用于升主动脉 TAWSS 的准确预测。这项研究证明了 SDR 在为患者特异性血流动力学模拟定制入口血流波形方面的重要性。调整良好的血流波形对于确保模拟结果符合患者特异性要求至关重要,从而提高计算工具在未来临床应用中的可信度和保真度。
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引用次数: 0
Closed-loop baroreflex model with biophysically detailed afferent pathway 具有生物物理详细传入路径的闭环气压反射模型。
IF 2.2 4区 医学 Q3 ENGINEERING, BIOMEDICAL Pub Date : 2024-07-25 DOI: 10.1002/cnm.3849
Luciano Gonçalves Fernandes, Lucas Omar Müller, Raúl Antonino Feijóo, Pablo Javier Blanco

In this work, we couple a lumped-parameter closed-loop model of the cardiovascular system with a physiologically-detailed mathematical description of the baroreflex afferent pathway. The model features a classical Hodgkin–Huxley current-type model for the baroreflex afferent limb (primary neuron) and for the second-order neuron in the central nervous system. The pulsatile arterial wall distension triggers a frequency-modulated sequence of action potentials at the afferent neuron. This signal is then integrated at the brainstem neuron model. The efferent limb, representing the sympathetic and parasympathetic nervous system, is described as a transfer function acting on heart and blood vessel model parameters in order to control arterial pressure. Three in silico experiments are shown here: a step increase in the aortic pressure to evaluate the functionality of the reflex arch, a hemorrhagic episode and an infusion simulation. Through this model, it is possible to study the biophysical dynamics of the ionic currents proposed for the afferent limb components of the baroreflex during the cardiac cycle, and the way in which currents dynamics affect the cardiovascular function. Moreover, this system can be further developed to study in detail each baroreflex loop component, helping to unveil the mechanisms involved in the cardiovascular afferent information processing.

在这项工作中,我们将心血管系统的整块参数闭环模型与巴反射传入通路的生理学详细数学描述相结合。该模型的气压反射传入肢(初级神经元)和中枢神经系统的二阶神经元均采用经典的霍奇金-赫胥黎电流型模型。脉动性动脉壁胀大在传入神经元触发频率调制的动作电位序列。该信号随后被整合到脑干神经元模型中。代表交感和副交感神经系统的传出神经肢被描述为作用于心脏和血管模型参数的传递函数,以控制动脉压力。这里展示了三个硅学实验:评估反射拱功能的主动脉压力阶跃增加、出血发作和输液模拟。通过该模型,可以研究在心动周期中为气压反射传入肢成分提出的离子电流的生物物理动态,以及电流动态影响心血管功能的方式。此外,该系统还可进一步发展,以详细研究每个巴反射环路成分,从而帮助揭示心血管传入信息处理的相关机制。
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引用次数: 0
Accuracy and efficiency of finite element head models: The role of finite element formulation and material laws 有限元头模型的精度和效率:有限元配方和材料定律的作用。
IF 2.2 4区 医学 Q3 ENGINEERING, BIOMEDICAL Pub Date : 2024-07-24 DOI: 10.1002/cnm.3851
Marcos S. Gomes, Gustavo P. Carmo, Mariusz Ptak, Fábio A. O. Fernandes, Ricardo J. Alves de Sousa

Traumatic brain injury is a significant problem worldwide. In the United States of America, around 1.7 million cases are documented annually, displaying the need for a deeper understanding of the effects on the human brain. The tests required for this assessment are very complex. Tests on cadavers may raise serious ethical questions, and in vivo crash tests are not viable. In this context, there is a great need to developing finite element head models (FEHM) to study the biomechanics of the tissues when submitted to a certain impact or acceleration/deceleration scenario. An excellent compromise between accuracy and CPU efficiency is always desirable for a FEHM, For this reason, this work focuses on the improvement of an existing head model, including the study of the behavior of the brain using distinct finite element types. The finite element type and formulation is of utmost importance for the general accuracy and efficiency of the models. Several validations were performed, comparing the simulation results against experimental data. The simulations with hexahedral elements, under specific conditions, obtained more accurate results with a lower computational cost. Using hexahedrals, a comparison was also performed using two material characterizations with more than 10 years apart, using the latest finite element head model validation experiment. Overall, the newer material model displays a less stiff response, although its implementation must always depend on the overall purpose of the model it is being applied to.

创伤性脑损伤是一个全球性的重大问题。在美国,每年约有 170 万例记录在案,这表明有必要深入了解脑外伤对人脑的影响。这种评估所需的测试非常复杂。在尸体上进行测试可能会引发严重的伦理问题,而活体碰撞测试又不可行。在这种情况下,亟需开发头部有限元模型(FEHM)来研究组织在受到特定撞击或加速/减速情况下的生物力学。因此,这项工作的重点是改进现有的头部模型,包括使用不同的有限元类型研究大脑的行为。有限元类型和公式对模型的总体精度和效率至关重要。我们进行了多次验证,将模拟结果与实验数据进行比较。在特定条件下,使用六面体元素的模拟结果更精确,计算成本更低。在使用六面体的同时,还使用最新的有限元头模型验证实验,对相隔 10 多年的两种材料特性进行了比较。总体而言,较新的材料模型显示出较小的刚性响应,尽管其实施必须始终取决于所应用模型的总体目的。
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引用次数: 0
Numerical investigation and optimization of innovative root canal irrigation needles with composite flow control structures 带有复合流量控制结构的创新型根管灌注针的数值研究与优化。
IF 2.2 4区 医学 Q3 ENGINEERING, BIOMEDICAL Pub Date : 2024-07-24 DOI: 10.1002/cnm.3852
Xiaoyu Sun, Youwei Tan, Ruirui Liu, Ping Li

Needle syringe irrigation is frequently used in root canal therapy, and the flow pattern during irrigation can be efficiently manipulated by means of passive flow control technique, resulting in expected irrigation performance improvement. Therefore, novel needles with composite flow control structures are numerically investigated and optimized in this study. Based on the 30G needle, six single/double side-vented needles with dimple and protrusion are proposed. Two flow rates in line with clinical applications, 5.3 and 8.6 m/s, are used in the analysis. Three performance parameters are investigated. The safety of the irrigation system is evaluated by the root canal apical pressure, whereas the irrigant extension and the flushing efficiency are evaluated by the extending depth and the effective cleaning area, respectively. The results demonstrate that the shear stress of the double-side-vented needle is higher while the irrigant extension is enhanced with a dimple structure. The performance of the double-side-vented needle with a dimple is superior to that of other designs, with up to 33% improvement in extending depth and a 22% increase in effective cleaning area over the prototype. New needles do not raise risk of irrigant extrusion. Furthermore, the effect of dimple depth and outlet angle are investigated. The needle with a dimple of 0.04 mm depth shows the highest extending depth within the confines of the investigation. The effective cleaning area is significantly influenced by the needle outlets, and the effective cleaning area expands with an increase in needle outlet angle, while the extending depth gradually declines.

根管治疗中经常使用针管灌洗,而灌洗过程中的流动模式可以通过被动流量控制技术进行有效控制,从而达到预期的灌洗效果。因此,本研究对具有复合流量控制结构的新型针头进行了数值研究和优化。在 30G 注射针的基础上,提出了六种带有凹陷和突起的单/双侧孔注射针。分析中使用了符合临床应用的两种流速,即 5.3 和 8.6 m/s。对三个性能参数进行了研究。根管根尖压力评估了灌洗系统的安全性,而延伸深度和有效清洁面积则分别评估了灌洗剂的延伸率和冲洗效率。结果表明,双侧通气针的剪切应力更高,而具有凹陷结构的冲洗剂延伸率更高。与原型针相比,双侧通气针的性能优于其他设计,延伸深度提高了 33%,有效清洁面积增加了 22%。新针头不会增加冲洗液挤出的风险。此外,还研究了窝深和出口角度的影响。在调查范围内,凹痕深度为 0.04 毫米的针具有最高的延伸深度。有效清洁面积受针头出口的影响很大,有效清洁面积随着针头出口角度的增加而扩大,而延伸深度则逐渐减小。
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引用次数: 0
Computational haemodynamics for pulmonary valve replacement by means of a reduced fluid-structure interaction model 通过简化流体与结构相互作用模型计算肺动脉瓣置换术的血液动力学。
IF 2.2 4区 医学 Q3 ENGINEERING, BIOMEDICAL Pub Date : 2024-07-22 DOI: 10.1002/cnm.3846
Elisabetta Criseo, Ivan Fumagalli, Alfio Quarteroni, Stefano Maria Marianeschi, Christian Vergara

Pulmonary valve replacement (PVR) consists of substituting a patient's original valve with a prosthetic one, primarily addressing pulmonary valve insufficiency, which is crucially relevant in Tetralogy of Fallot repairment. While extensive clinical and computational literature on aortic and mitral valve replacements is available, PVR's post-procedural haemodynamics in the pulmonary artery and the impact of prosthetic valve dynamics remain significantly understudied. Addressing this gap, we introduce a reduced Fluid–Structure Interaction (rFSI) model, applied for the first time to the pulmonary valve. This model couples a three-dimensional computational representation of pulmonary artery haemodynamics with a one-degree-of-freedom model to account for valve structural mechanics. Through this approach, we analyse patient-specific haemodynamics pre and post PVR. Patient-specific geometries, reconstructed from CT scans, are virtually equipped with a template valve geometry. Boundary conditions for the model are established using a lumped-parameter model, fine-tuned based on clinical patient data. Our model accurately reproduces patient-specific haemodynamic changes across different scenarios: pre-PVR, six months post-PVR, and a follow-up condition after a decade. It effectively demonstrates the impact of valve implantation on sustaining the diastolic pressure gradient across the valve. The numerical results indicate that our valve model is able to reproduce overall physiological and/or pathological conditions, as preliminary assessed on two different patients. This promising approach provides insights into post-PVR haemodynamics and prosthetic valve effects, shedding light on potential implications for patient-specific outcomes.

肺动脉瓣置换术(PVR)是用人工瓣膜替代患者原有的瓣膜,主要解决肺动脉瓣功能不全的问题,这与法洛氏四联症修复术密切相关。虽然已有大量关于主动脉瓣和二尖瓣置换术的临床和计算文献,但对 PVR 术后肺动脉血流动力学以及人工瓣膜动力学的影响研究仍显不足。为了弥补这一不足,我们引入了一个简化的流体-结构相互作用(rFSI)模型,并首次将其应用于肺动脉瓣。该模型将肺动脉血流动力学的三维计算表示与单自由度模型相结合,以考虑瓣膜结构力学。通过这种方法,我们分析了 PVR 前后患者的血流动力学。根据 CT 扫描重建的患者特异性几何图形实际上配备了瓣膜几何模板。模型的边界条件是通过一个基于临床患者数据进行微调的集合参数模型建立的。我们的模型准确再现了患者在不同情况下的血流动力学变化:瓣膜置换术前、瓣膜置换术后六个月以及十年后的随访情况。它有效地展示了瓣膜植入对维持瓣膜舒张压梯度的影响。数值结果表明,我们的瓣膜模型能够再现整体生理和/或病理状况,这是在两名不同患者身上进行的初步评估。这种前景广阔的方法有助于深入了解瓣膜植入术后的血流动力学和人工瓣膜的影响,从而揭示对特定患者预后的潜在影响。
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引用次数: 0
Computational fluid dynamics of bladder voiding using 3D dynamic MRI 利用三维动态磁共振成像计算膀胱排尿的流体动力学。
IF 2.2 4区 医学 Q3 ENGINEERING, BIOMEDICAL Pub Date : 2024-07-15 DOI: 10.1002/cnm.3850
Labib Shahid, Juan Pablo Gonzalez-Pereira, Cody Johnson, Wade Bushman, Alejandro Roldán-Alzate

Over the last couple of decades, image-based computational fluid dynamics (CFD) has revolutionized cardiovascular research by uncovering hidden features of wall strain, impact of vortices, and its use in treatment planning, as examples, that were simply not evident in the gold-standard catheterization studies done previously. In the work presented here, we have applied magnetic resonance imaging (MRI)-based CFD to study bladder voiding and to demonstrate the feasibility and potential of this approach. We used 3D dynamic MRI to image the bladder and urethra during voiding. A surface mesh processing tool was developed to process the bladder wall prior to executing a wall-motion driven CFD simulation of the bladder and urethra. The obtained flow rate and pressure were used to calculate urodynamic nomograms, which are currently used in the clinical setting to assess bladder voiding dysfunction. These nomograms concluded that our healthy volunteer has an unobstructed bladder and normal contractility. We calculated the work done to void the bladder and propose this as an additional quantitative metric to comprehensively assess bladder function. Further, we discuss the areas that would improve this relatively new methodology of image-based CFD in urodynamics.

在过去几十年中,基于图像的计算流体动力学(CFD)揭示了心血管壁应变的隐藏特征、涡流的影响及其在治疗规划中的应用等,从而彻底改变了心血管研究,而这些在以前的金标准导管研究中根本无法显现。在本文介绍的工作中,我们将基于磁共振成像(MRI)的 CFD 应用于膀胱排尿研究,并证明了这种方法的可行性和潜力。我们使用三维动态磁共振成像技术对排尿过程中的膀胱和尿道进行成像。在对膀胱和尿道执行壁运动驱动的 CFD 模拟之前,我们开发了一种表面网格处理工具来处理膀胱壁。获得的流速和压力被用于计算尿动力学提名图,该提名图目前用于临床评估膀胱排尿功能障碍。这些提名图的结论是,我们的健康志愿者膀胱通畅,收缩力正常。我们计算了排空膀胱所做的功,并建议将其作为全面评估膀胱功能的额外定量指标。此外,我们还讨论了在尿动力学中改进基于图像的 CFD 这种相对较新方法的领域。
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引用次数: 0
Computational biomechanics for a standing human body: Modal analysis and simulation 站立人体的计算生物力学:模态分析与模拟
IF 2.2 4区 医学 Q3 ENGINEERING, BIOMEDICAL Pub Date : 2024-07-11 DOI: 10.1002/cnm.3841
Goong Chen, Matthew M. Scully, Jingtong Huang, Alexey Sergeev, Jing Yang, Chunqiu Wei, Patrick Monday, Leon Cohen, Xingong Cheng, Sanyang Liu, Junmin Wang, Shuqin Zhou

We develop computational mechanical modeling and methods for the analysis and simulation of the motions of a human body. This type of work is crucial in many aspects of human life, ranging from comfort in riding, the motion of aged persons, sports performance and injuries, and many ergonomic issues. A prevailing approach for human motion studies is through lumped parameter models containing discrete masses for the parts of the human body with empirically determined spring, mass, damping coefficients. Such models have been effective to some extent; however, a much more faithful modeling method is to model the human body as it is, namely, as a continuum. We present this approach, and for comparison, we choose two digital CAD models of mannequins for a standing human body, one from the versatile software package LS-DYNA and another from open resources with some of our own adaptations. Our basic view in this paper is to regard human motion as a perturbation and vibration from an equilibrium position which is upright standing. A linear elastodynamic model is chosen for modal analysis, but a full nonlinear viscoelastoplastic extension is possible for full-body simulation. The motion and vibration of these two mannequin models is analyzed by modal analysis, where the normal vibration modes are determined. LS-DYNA is used as the supercomputing and simulation platform. Four sets of low-frequency modes are tabulated, discussed, visualized, and compared. Higher frequency modes are also selectively displayed. We have found that these modes of motion and vibration form intrinsic basic modes of biomechanical motion of the human body. This view is supported by our finding of the upright walking motion as a low-frequency mode in modal analysis. Such a “walking mode” shows the in-phase and out-of-phase movements between the legs and arms on the left and right sides of a human body, implying that this walking motion is spontaneous, likely not requiring any directives from the brain. Dynamic motions of CAD mannequins are also simulated by drop tests for comparisons and the validity of the models is discussed through Fourier frequency analysis. All computed modes of motion are collected in several sets of video animations for ease of visualization. Samples of LS-DYNA computer codes are also included for possible use by other researchers.

我们开发用于分析和模拟人体运动的计算机械建模和方法。这类工作对人类生活的许多方面都至关重要,包括乘车舒适度、老年人的运动、运动表现和损伤以及许多人体工程学问题。人体运动研究的一种普遍方法是通过包含离散质量的集合参数模型来研究人体各部分的运动,并根据经验确定弹簧、质量和阻尼系数。这种模型在一定程度上是有效的;然而,一种更忠实的建模方法是将人体作为一个连续体来建模。我们介绍了这种方法,为了进行比较,我们选择了两个站立人体模型的数字 CAD 模型,一个来自多功能软件包 LS-DYNA,另一个来自开放资源,并经过我们自己的一些调整。本文的基本观点是将人体运动视为从直立平衡位置开始的扰动和振动。在进行模态分析时,我们选择了线性弹性力学模型,但在进行全身模拟时,我们也可能采用完全非线性粘弹性扩展模型。这两个人体模型的运动和振动是通过模态分析来确定法向振动模态的。采用 LS-DYNA 作为超级计算和仿真平台。对四组低频模态进行了列表、讨论、可视化和比较。高频模式也有选择地显示出来。我们发现,这些运动和振动模式构成了人体生物力学运动的内在基本模式。在模态分析中,我们发现直立行走运动是一种低频模态,这为我们的观点提供了支持。这种 "行走模式 "显示了人体左右两侧腿部和手臂之间的同相和异相运动,意味着这种行走运动是自发的,很可能不需要大脑的任何指令。此外,还通过跌落测试模拟了 CAD 人体模型的动态运动,并通过傅里叶频率分析讨论了模型的有效性。所有计算出的运动模式都收集在几组视频动画中,以便于可视化。此外还包括 LS-DYNA 计算机代码样本,供其他研究人员使用。
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引用次数: 0
Computational comparison study of virtual compression and shear test for estimation of apparent elastic moduli under various boundary conditions 虚拟压缩和剪切试验的计算对比研究,用于估算各种边界条件下的表观弹性模量。
IF 2.2 4区 医学 Q3 ENGINEERING, BIOMEDICAL Pub Date : 2024-07-09 DOI: 10.1002/cnm.3845
Jisun Kim, Jung Jin Kim

Virtual compression tests based on finite element analysis are representative noninvasive methods to evaluate bone strength. However, owing to the characteristic porous structure of bones, the material obtained from micro-computed tomography images in the finite-element model is not uniformly distributed. These characteristics cause differences in the apparent elastic moduli depending on the boundary conditions and affect the accuracy of bone-strength evaluation. Therefore, this study aimed to evaluate and compare the apparent elastic moduli under various, virtual-compression and shear-test boundary conditions. Four, nonuniform models were constructed with increasing model complexity. For representative boundary conditions, two, different, testing directions, and constrained surfaces were applied. As a result, the apparent elastic moduli of the nonuniform model varied up to 55.2% based on where the constrained surface was located in the single-end-cemented condition. Additionally, when connectivity in the test direction was lost, the accuracy of the apparent elastic moduli was low. A graphical comparison showed that the equivalent-stress distribution was more advantageous for analyzing load transferability and physical behavior than the strain-energy distribution. These results clearly show that the prediction accuracy of the apparent elastic moduli can be guaranteed if the boundary condition on the constraint and loading surfaces of the nonuniform model are applied symmetrically and the connectivity of the elements in the testing direction is well maintained. This study will aid in precision improvement of bone-strength-indicator determination for osteoporosis prevention.

基于有限元分析的虚拟压缩试验是评估骨强度的代表性无创方法。然而,由于骨骼具有多孔结构的特点,从有限元模型中的微型计算机断层扫描图像中获得的材料并不是均匀分布的。这些特征会导致表观弹性模量因边界条件的不同而产生差异,影响骨强度评估的准确性。因此,本研究旨在评估和比较各种虚拟压缩和剪切测试边界条件下的表观弹性模量。随着模型复杂程度的增加,我们构建了四个非均匀模型。对于具有代表性的边界条件,应用了两个不同的测试方向和约束表面。因此,在单端加固条件下,根据约束面的位置,非均匀模型的表观弹性模量变化高达 55.2%。此外,当测试方向上的连通性丧失时,表观弹性模量的精确度也很低。图形比较显示,等效应力分布比应变能分布更有利于分析荷载传递性和物理行为。这些结果清楚地表明,如果在非均匀模型的约束面和加载面上对称施加边界条件,并保持测试方向上元素的连通性,就能保证表观弹性模量的预测精度。这项研究将有助于提高骨强度指标测定的精度,从而预防骨质疏松症。
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引用次数: 0
Effect of dispersive electrode position (anterior vs. posterior) in epicardial radiofrequency ablation of ventricular wall: A computer simulation study 心外膜射频消融室壁时分散电极位置(前部与后部)的影响:计算机模拟研究。
IF 2.2 4区 医学 Q3 ENGINEERING, BIOMEDICAL Pub Date : 2024-07-09 DOI: 10.1002/cnm.3847
Ramiro M. Irastorza, Claudio Hadid, Enrique Berjano

An epicardial approach is often used in radiofrequency (RF) catheter ablation to ablate ventricular tachycardia when an endocardial approach fails. Our objective was to analyze the effect of the position of the dispersive patch (DP) on lesion size using computer modeling during epicardial approach. We compared the posterior position (patient's back), commonly used in clinical practice, to the anterior position (patient's chest). The model considered ventricular wall thicknesses between 4 and 8 mm, and electrode insertion depths between .3 and .7 mm. RF pulses were simulated with 20 W of power for 30 s duration. Statistically significant differences (P < .001) were found between both DP positions in terms of baseline impedance, RF current (at 15 s) and thermal lesion size. The anterior position involved lower impedance (130.8 ± 4.7 vs. 146.2 ± 4.9 Ω) and a higher current (401.5 ± 5.6 vs. 377.5 ± 5.1 mA). The anterior position created lesion sizes larger than the posterior position: 8.9 ± 0.4 vs. 8.4 ± 0.4 mm in maximum width, 8.6 ± 0.4 vs. 8.1 ± 0.4 mm in surface width, and 4.5 ± 0.4 vs. 4.3 ± 0.4 mm in depth. Our results suggest that: (1) the redirection of the RF currents due to repositioning the PD has little impact on lesion size and only affects baseline impedance, and (2) the differences in lesion size are only 0.5 mm wider and 0.2 mm deeper for the anterior position, which does not seem to have a clinical impact in the context of VT ablation.

在射频(RF)导管消融术中,当心内膜入路失败时,通常使用心外膜入路消融室性心动过速。我们的目的是利用计算机建模分析心外膜入路时分散贴片(DP)位置对病灶大小的影响。我们比较了临床上常用的后位(患者背部)和前位(患者胸部)。模型考虑的心室壁厚度在 4 至 8 毫米之间,电极插入深度在 0.3 至 0.7 毫米之间。模拟射频脉冲的功率为 20 瓦,持续时间为 30 秒。统计学差异(P
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引用次数: 0
Breast segmentation in infrared thermography from characteristical inframammary shape 根据乳房下形状特征对红外热成像中的乳房进行分割。
IF 2.2 4区 医学 Q3 ENGINEERING, BIOMEDICAL Pub Date : 2024-07-04 DOI: 10.1002/cnm.3843
Francisco J. Alvarez-Padilla, Jorge L. Flores-Nunez, Juan R. Alvarez-Padilla, Francisco J. Gonzalez, Antonio Oceguera-Villanueva, Brian A. Gutierrez-Quiroz

Infrared thermography is gaining relevance in breast cancer assessment. For this purpose, breast segmentation in thermograms is an important task for performing automatic image analysis and detecting possible temperature changes that indicate the presence of malignancy. However, it is not a simple task since the breast limit borders, especially the top borders, often have low contrast, making it difficult to isolate the breast area. Several algorithms have been proposed for breast segmentation, but these highly depend on the contrast at the lower breast borders and on filtering algorithms to remove false edges. This work focuses on taking advantage of the distinctive inframammary shape to simplify the definition of the lower breast border, regardless of the contrast level, which indeed also provides a strong anatomical reference to support the definition of the poorly marked upper boundary of the breasts, which has been one of the major challenges in the literature. In order to demonstrate viability of the proposed technique for an automatic breast segmentation, we applied it to a database with 180 thermograms and compared their results with those reported by others in the literature. We found that our approach achieved a high performance, in terms of Intersection over Union of 0.934, even higher than that reported by artificial intelligence algorithms. The performance is invariant to breast sizes and thermal contrast of the images.

红外热成像技术在乳腺癌评估中的应用越来越广泛。为此,热成像中的乳房分割是一项重要任务,可用于进行自动图像分析和检测表明存在恶性肿瘤的可能温度变化。然而,这并不是一项简单的任务,因为乳房的极限边界,尤其是顶部边界,通常对比度较低,很难将乳房区域分离出来。目前已经提出了几种乳房分割算法,但这些算法在很大程度上依赖于乳房下边界的对比度和滤波算法来去除虚假边缘。这项工作的重点是利用乳房下部的独特形状来简化乳房下部边界的定义,无论对比度如何,这实际上也为乳房上部边界的定义提供了强有力的解剖学参考,而这一直是文献中的主要挑战之一。为了证明所提出的技术在自动乳房分割中的可行性,我们将其应用于一个包含 180 张热敏图的数据库,并将其结果与其他文献中报告的结果进行了比较。我们发现,我们的方法取得了很高的性能,交集大于联合度为 0.934,甚至高于人工智能算法。这种性能不受乳房大小和图像热对比度的影响。
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引用次数: 0
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International Journal for Numerical Methods in Biomedical Engineering
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