Finite Element Analysis of Radio-Frequency Ablation in a Reconstructed Realistic Hepatic Geometry

2002 ◽  
Author(s):  
Ajit K. Pandey ◽  
Isaac Chang ◽  
Matthew R. Myers ◽  
Rupak K. Banerjee
Keyword(s):  
Radio Frequency ◽  
Temperature Rise ◽  
Patient Specific ◽  
Hepatic Tissue ◽  
Specific Information ◽  
Rf Ablation ◽  
Operational Parameters ◽  
Time Duration ◽  
Porcine Liver ◽  
Element Analysis

Radio-frequency (RF) ablation is a minimally invasive procedure that has the potential for widespread use in hepatic cancer therapy. In the procedure, RF current is applied to the tissue, resulting in the conversion of electrical to heat energy and thus, a rise in temperature, with the goal of eventual tumor necrosis. Potential complications from the procedure include insufficient heating of large tumors, resulting in tumor recursion, as well as excessive thermal damage to healthy tissue. Mathematical models are valuable in predicting the temperature rise within the organ during RF ablation, thereby enhancing the success rate of the procedure. Eventually, models can be used to guide ablation procedures, by predicting the optimal set of operational parameters e.g., catheter probe geometry and placement, given patient-specific information. The present study focuses on the analysis of temperature rise within a reconstructed model of a realistic three-dimensional (3D) section of a porcine liver during RF ablation. This study calculates the effect of blood flow through arteries as well as perfusion through the liver on the time-dependent temperature distribution near the RF ablation probe (Figure 1). For a time duration of 30 min of an ablation procedure, a temperature of about 80°C could be achieved over a diameter of about 4 cm with the present RF probe. As an initial step, the present study includes isotropic hepatic tissue and blood properties.

Radio-Frequency Ablation in a Realistic Reconstructed Hepatic Tissue

2006 ◽  
Vol 129 (3) ◽  
pp. 354-364 ◽  
Author(s):  
Prasanna Hariharan ◽  
Isaac Chang ◽  
Matthew R. Myers ◽  
Rupak K. Banerjee
Keyword(s):  
Temperature Rise ◽  
Cell Damage ◽  
Three Dimensional ◽  
Thermal Response ◽  
Tumor Location ◽  
Tissue Temperature ◽  
Patient Specific ◽  
Hepatic Tissue ◽  
Thermal Dose ◽  
Element Mesh

This study uses a reconstructed vascular geometry to evaluate the thermal response of tissue during a three-dimensional radiofrequency (rf) tumor ablation. MRI images of a sectioned liver tissue containing arterial vessels are processed and converted into a finite-element mesh. A rf heat source in the form of a spherically symmetric Gaussian distribution, fit from a previously computed profile, is employed. Convective cooling within large blood vessels is treated using direct physical modeling of the heat and momentum transfer within the vessel. Calculations of temperature rise and thermal dose are performed for transient rf procedures in cases where the tumor is located at three different locations near the bifurcation point of a reconstructed artery. Results demonstrate a significant dependence of tissue temperature profile on the reconstructed vasculature and the tumor location. Heat convection through the arteries reduced the steady-state temperature rise, relative to the no-flow case, by up to 70% in the targeted volume. Blood flow also reduced the thermal dose value, which quantifies the extent of cell damage, from ∼3600min, for the no-flow condition, to 10min for basal flow (13.8cm∕s). Reduction of thermal dose below the threshold value of 240min indicates ablation procedures that may inadequately elevate the temperature in some regions, thereby permitting possible tumor recursion. These variations are caused by vasculature tortuosity that are patient specific and can be captured only by the reconstruction of the realistic geometry.

Tailoring Communications for Primary Care Settings

1998 ◽  
Vol 37 (02) ◽  
pp. 171-178 ◽  
Author(s):  
B. Glassman ◽  
B. K. Rimer
Keyword(s):  
Primary Care ◽  
Health Professionals ◽  
Contact Time ◽  
Behavioral Changes ◽  
Patient Specific ◽  
Specific Information ◽  
Medical Settings ◽  
Primary Care Settings ◽  
Professional Contact ◽  
Tailored Communications

AbstractIn more and more medical settings, physicians have less and less time to be effective communicators. To be effective, they need accurate, current information about their patients. Tailored health communications can facilitate positive patient-provider communications and foster behavioral changes conducive to health. Tailored communications (TCs) are produced for an individual based on information about that person. The focus of this report is on tailored print communications (TPCs). TPCs also enhance the process of evaluation, because they require a database and the collection of patient-specific information. We present a Tailoring Model for Primary Care that describes the steps involved in creating TPCs. We also provide examples from three ongoing studies in which TPCs are being used in order to illustrate the kinds of variables used for tailoring the products that are developed and how evaluation is conducted. TPCs offer opportunities to expand the reach of health professionals and to give personalized, individualized massages in an era of shrinking professional contact time.

scholarly journals Assessment of patient specific information in the wild on fundus photography and optical coherence tomography

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Marion R. Munk ◽  
Thomas Kurmann ◽  
Pablo Márquez-Neila ◽  
Martin S. Zinkernagel ◽  
Sebastian Wolf ◽  
...  
Keyword(s):  
Deep Learning ◽  
Cross Sections ◽  
Underlying Disease ◽  
Geographic Atrophy ◽  
Clinical Population ◽  
Fundus Photography ◽  
Peak Performance ◽  
Patient Specific ◽  
Specific Information ◽  
Fundus Images

AbstractIn this paper we analyse the performance of machine learning methods in predicting patient information such as age or sex solely from retinal imaging modalities in a heterogeneous clinical population. Our dataset consists of N = 135,667 fundus images and N = 85,536 volumetric OCT scans. Deep learning models were trained to predict the patient’s age and sex from fundus images, OCT cross sections and OCT volumes. For sex prediction, a ROC AUC of 0.80 was achieved for fundus images, 0.84 for OCT cross sections and 0.90 for OCT volumes. Age prediction mean absolute errors of 6.328 years for fundus, 5.625 years for OCT cross sections and 4.541 for OCT volumes were observed. We assess the performance of OCT scans containing different biomarkers and note a peak performance of AUC = 0.88 for OCT cross sections and 0.95 for volumes when there is no pathology on scans. Performance drops in case of drusen, fibrovascular pigment epitheliuum detachment and geographic atrophy present. We conclude that deep learning based methods are capable of classifying the patient’s sex and age from color fundus photography and OCT for a broad spectrum of patients irrespective of underlying disease or image quality. Non-random sex prediction using fundus images seems only possible if the eye fovea and optic disc are visible.

scholarly journals Depression patient-derived cortical neurons reveal potential biomarkers for antidepressant response

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Yishai Avior ◽  
Shiri Ron ◽  
Dana Kroitorou ◽  
Claudia Albeldas ◽  
Vitaly Lerner ◽  
...  
Keyword(s):  
Cortical Neurons ◽  
Antidepressant Treatment ◽  
Patient Specific ◽  
Specific Gene ◽  
Specific Information ◽  
Patient Response ◽  
Patient Will ◽  
Gene Expression Alterations ◽  
Treatment Alternatives

AbstractMajor depressive disorder is highly prevalent worldwide and has been affecting an increasing number of people each year. Current first line antidepressants show merely 37% remission, and physicians are forced to use a trial-and-error approach when choosing a single antidepressant out of dozens of available medications. We sought to identify a method of testing that would provide patient-specific information on whether a patient will respond to a medication using in vitro modeling. Patient-derived lymphoblastoid cell lines from the Sequenced Treatment Alternatives to Relieve Depression study were used to rapidly generate cortical neurons and screen them for bupropion effects, for which the donor patients showed remission or non-remission. We provide evidence for biomarkers specific for bupropion response, including synaptic connectivity and morphology changes as well as specific gene expression alterations. These biomarkers support the concept of personalized antidepressant treatment based on in vitro platforms and could be utilized as predictors to patient response in the clinic.

scholarly journals Computational and experimental mechanical performance of a new everolimus-eluting stent purpose-built for left main interventions

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Saurabhi Samant ◽  
Wei Wu ◽  
Shijia Zhao ◽  
Behram Khan ◽  
Mohammadali Sharzehee ◽  
...  
Keyword(s):  
Structural Integrity ◽  
Mechanical Performance ◽  
Experimental Studies ◽  
Patient Specific ◽  
Wall Structure ◽  
Left Main ◽  
Element Analysis ◽  
Stent Expansion ◽  
Radial Strength ◽  
Different Diameters

AbstractLeft main (LM) coronary artery bifurcation stenting is a challenging topic due to the distinct anatomy and wall structure of LM. In this work, we investigated computationally and experimentally the mechanical performance of a novel everolimus-eluting stent (SYNERGY MEGATRON) purpose-built for interventions to large proximal coronary segments, including LM. MEGATRON stent has been purposefully designed to sustain its structural integrity at higher expansion diameters and to provide optimal lumen coverage. Four patient-specific LM geometries were 3D reconstructed and stented computationally with finite element analysis in a well-validated computational stent simulation platform under different homogeneous and heterogeneous plaque conditions. Four different everolimus-eluting stent designs (9-peak prototype MEGATRON, 10-peak prototype MEGATRON, 12-peak MEGATRON, and SYNERGY) were deployed computationally in all bifurcation geometries at three different diameters (i.e., 3.5, 4.5, and 5.0 mm). The stent designs were also expanded experimentally from 3.5 to 5.0 mm (blind analysis). Stent morphometric and biomechanical indices were calculated in the computational and experimental studies. In the computational studies the 12-peak MEGATRON exhibited significantly greater expansion, better scaffolding, smaller vessel prolapse, and greater radial strength (expressed as normalized hoop force) than the 9-peak MEGATRON, 10-peak MEGATRON, or SYNERGY (p < 0.05). Larger stent expansion diameters had significantly better radial strength and worse scaffolding than smaller stent diameters (p < 0.001). Computational stenting showed comparable scaffolding and radial strength with experimental stenting. 12-peak MEGATRON exhibited better mechanical performance than the 9-peak MEGATRON, 10-peak MEGATRON, or SYNERGY. Patient-specific computational LM stenting simulations can accurately reproduce experimental stent testing, providing an attractive framework for cost- and time-effective stent research and development.

Thermo-Mechanical Modeling and Analysis of Equal Channel Angular Pressing

2005 ◽  
Vol 23 ◽  
pp. 263-266 ◽  
Author(s):  
Qing Xiang Pei ◽  
B.H. Hu ◽  
C. Lu
Keyword(s):  
Equal Channel Angular Pressing ◽  
Temperature Rise ◽  
Flow Behavior ◽  
Material Model ◽  
Workpiece Material ◽  
Element Analysis ◽  
Modeling And Analysis ◽  
Die Geometry ◽  
Angular Pressing ◽  
Good Agreement

Thermo-mechanical finite element analysis was carried out to study the deformation behavior and temperature distribution during equal channel angular pressing (ECAP). The material model used is the Johnson-Cook constitution model that can consider the multiplication effect of strain, strain rate, and temperature on the flow stress. The effects of pressing speed, pressing temperature, workpiece material and die geometry on the temperature rise and flow behavior during ECAP process were investigated. The simulated temperature rise due to deformation heating was compared with published experimental results and a good agreement was obtained. Among the various die geometries studied, the two-turn die with 0° round corner generates the highest and most uniform plastic strain in the workpiece.

Abdominal Aortic Aneurysm: From Clinical Imaging to Realistic Replicas

2013 ◽  
Vol 136 (1) ◽  
Author(s):  
Sergio Ruiz de Galarreta ◽  
Aitor Cazón ◽  
Raúl Antón ◽  
Ender A. Finol
Keyword(s):  
Wall Thickness ◽  
Physiological Stress ◽  
Ex Vivo ◽  
Casting Process ◽  
Aortic Aneurysms ◽  
Optical Methods ◽  
Patient Specific ◽  
Uniaxial Tensile ◽  
Element Analysis ◽  
Abdominal Aortic

The goal of this work is to develop a framework for manufacturing nonuniform wall thickness replicas of abdominal aortic aneurysms (AAAs). The methodology was based on the use of computed tomography (CT) images for virtual modeling, additive manufacturing for the initial physical replica, and a vacuum casting process and range of polyurethane resins for the final rubberlike phantom. The average wall thickness of the resulting AAA phantom was compared with the average thickness of the corresponding patient-specific virtual model, obtaining an average dimensional mismatch of 180 μm (11.14%). The material characterization of the artery was determined from uniaxial tensile tests as various combinations of polyurethane resins were chosen due to their similarity with ex vivo AAA mechanical behavior in the physiological stress configuration. The proposed methodology yields AAA phantoms with nonuniform wall thickness using a fast and low-cost process. These replicas may be used in benchtop experiments to validate deformations obtained with numerical simulations using finite element analysis, or to validate optical methods developed to image ex vivo arterial deformations during pressure-inflation testing.

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