Deformable Image Registration Between Cardiac PET Images Encompassing a Range of Physical Heart Sizes

2011 ◽  
Author(s):  
Benjamin R. Coleman ◽  
Alexander I. Veress
Keyword(s):  
Mechanical Performance ◽  
Fe Analysis ◽  
Material Behavior ◽  
Patient Specific ◽  
Stress And Strain ◽  
Myocardial Tissue ◽  
Cardiac Pet ◽  
Considerable Research ◽  
Deformation Stress

Cardiac mechanical performance depends upon myocardial tissue elongation and contraction. Deformation, stress and strain within the myofibers provide valuable information about potential tissue adaptation [1]. Specifically, the stress state of the tissue is believed to drive remodeling of the myocardium. Because it is not possible to measure in-vivo stress in the human heart, considerable research has gone into developing patient specific, mathematical models of the heart based on finite element (FE) analysis and cardiac imaging [2, 3]. Stress estimates from these models could yield valuable information about of the material behavior of the myocardium that would provide valuable information for research into cardiac pathologies.

scholarly journals In Silico Performance of a Recellularized Tissue-Engineered Transcatheter Aortic Valve

2019 ◽  
Vol 141 (6) ◽  
Author(s):  
Christopher Noble ◽  
Joshua Choe ◽  
Susheil Uthamaraj ◽  
Milton Deherrera ◽  
Amir Lerman ◽  
...  
Keyword(s):  
Mechanical Behavior ◽  
Heart Valves ◽  
Mechanical Response ◽  
Mechanical Performance ◽  
Fe Analysis ◽  
Model Parameters ◽  
Biaxial Testing ◽  
Principal Stresses

Commercially available heart valves have many limitations, such as a lack of remodeling, risk of calcification, and thromboembolic problems. Many state-of-the-art tissue-engineered heart valves (TEHV) rely on recellularization to allow remodeling and transition to mechanical behavior of native tissues. Current in vitro testing is insufficient in characterizing a soon-to-be living valve due to this change in mechanical response; thus, it is imperative to understand the performance of an in situ valve. However, due to the complex in vivo environment, this is difficult to accomplish. Finite element (FE) analysis has become a standard tool for modeling mechanical behavior of heart valves; yet, research to date has mostly focused on commercial valves. The purpose of this study has been to evaluate the mechanical behavior of a TEHV material before and after 6 months of implantation in a rat subdermis model. This model allows the recellularization and remodeling potential of the material to be assessed via a simple and inexpensive means prior to more complex ovine orthotropic studies. Biaxial testing was utilized to evaluate the mechanical properties, and subsequently, constitutive model parameters were fit to the data to allow mechanical performance to be evaluated via FE analysis of a full cardiac cycle. Maximum principal stresses and strains from the leaflets and commissures were then analyzed. The results of this study demonstrate that the explanted tissues had reduced mechanical strength compared to the implants but were similar to the native tissues. For the FE models, this trend was continued with similar mechanical behavior in explant and native tissue groups and less compliant behavior in implant tissues. Histology demonstrated recellularization and remodeling although remodeled collagen had no clear directionality. In conclusion, we observed successful recellularization and remodeling of the tissue giving confidence to our TEHV material; however, the mechanical response indicates the additional remodeling would likely occur in the aortic/pulmonary position.

Impact of Patient-Specific In Vivo Vessel Material Properties on Carotid Atherosclerotic Plaque Stress/Strain Calculations

2019 ◽  
Vol 16 (03) ◽  
pp. 1842002 ◽  
Author(s):  
Qingyu Wang ◽  
Dalin Tang ◽  
Gador Canton ◽  
Thomas S. Hatsukami ◽  
Kristen L. Billiar ◽  
...  
Keyword(s):  
Material Properties ◽  
Carotid Plaque ◽  
Computational Models ◽  
Patient Specific ◽  
Stress And Strain ◽  
Carotid Atherosclerotic Plaque ◽  
Plaque Vulnerability ◽  
Material Models ◽  
Vessel Material

Patient-specific vessel material properties are in general lacking in image-based computational models. Carotid plaque stress and strain conditions with in vivo material and old material models were investigated (8 patients, 16 plaques). Plaque models using patient-specific in vivo vessel material properties showed significant differences from models using old material properties from the literature on stress and strain calculations. These differences demonstrated that models using in vivo material properties could improve the accuracy of stress and strain calculations which could potentially lead to more accurate plaque vulnerability assessment.

Patient-Specific Finite Element Modeling of Mitral Valve Dynamic Deformation

2012 ◽  
Author(s):  
Qian Wang ◽  
Wei Sun
Keyword(s):  
Finite Element ◽  
Mitral Valve ◽  
Left Ventricle ◽  
Dynamic Deformation ◽  
Patient Specific ◽  
Stress And Strain ◽  
Prosthetic Devices ◽  
In Vivo Experiments ◽  
Normal Mitral Valve

Mitral valve is a two-leaflet valve that is located between the left atrium and the left ventricle of the heart. In order to successfully replace or repair mitral valve and develop effective prosthetic devices, it is critical to understand the in vivo mechanics of the normal mitral valve. Although research has been conducted to investigate animal mitral valve strains by in vivo experiments, it is still very challenging to obtain accurate in vivo stress and strain information of the human mitral valve.

Direct Measurement of the Permeability of Human Cervical Tissue

2013 ◽  
Vol 135 (2) ◽  
Author(s):  
Michael Fernandez ◽  
Joy Vink ◽  
Kyoko Yoshida ◽  
Ronald Wapner ◽  
Kristin M. Myers
Keyword(s):  
Mechanical Behavior ◽  
Material Behavior ◽  
Patient Specific ◽  
Diagnostic Tools ◽  
Hydraulic Permeability ◽  
Cervical Tissue ◽  
Large Variability ◽  
Developmental Problems ◽  
External Forces

The mechanical integrity of the uterine cervix is critical for a pregnancy to successfully reach full term. It must be strong to retain the fetus throughout gestation and then undergo a remodeling and softening process before labor for delivery of the fetus. It is believed that cervical insufficiency (CI), a condition in pregnancy resulting in preterm birth (PTB), is related to a cervix with compromised mechanical strength which cannot resist deformation caused by external forces generated by the growing fetus. Such PTBs are responsible for infant developmental problems and in severe cases infant mortality. To understand the etiologies of CI, our overall research goal is to investigate the mechanical behavior of the cervix. Permeability is a mechanical property of hydrated collagenous tissues that dictates the time-dependent response of the tissue to mechanical loading. The goal of this study was to design a novel soft tissue permeability testing device and to present direct hydraulic permeability measurements of excised nonpregnant (NP) and pregnant (PG) human cervical tissue from women with different obstetric histories. Results of hydraulic permeability testing indicate repeatability for specimens from single patients, with an order of magnitude separating the NP and PG group means (2.1 ± 1.4×10-14 and 3.2 ± 4.8×10-13m4/N·s, respectively), and large variability within the NP and PG sample groups. Differences were found between samples with similar obstetric histories, supporting the view that medical history may not be a good predictor of permeability (and therefore mechanical behavior) and highlighting the need for patient-specific measurements of cervical mechanical properties. The permeability measurements from this study will be used in future work to model the constitutive material behavior of cervical tissue and to develop in vivo diagnostic tools to stage the progression of labor.

scholarly journals Influence of aging on the in vivo properties of human patellar tendon

2008 ◽  
Vol 105 (6) ◽  
pp. 1907-1915 ◽  
Author(s):  
C. C. Carroll ◽  
J. M. Dickinson ◽  
J. M. Haus ◽  
G. A. Lee ◽  
C. J. Hollon ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Patellar Tendon ◽  
Signal Intensity ◽  
Knee Extensors ◽  
Stress And Strain ◽  
Force Output ◽  
Cross Sectional ◽  
Magnetic Resonance Imaging Mri ◽  
Deformation Stress

Tendons are important for optimal muscle force transfer to bone and play a key role in functional ability. Changes in tendon properties with aging could contribute to declines in physical function commonly associated with aging. We investigated the in vivo mechanical properties of the patellar tendon in 37 men and women [11 young (27 ± 1 yr) and 26 old (65 ± 1 yr)] using ultrasonography and magnetic resonance imaging (MRI). Patella displacement relative to the tibia was monitored with ultrasonography during ramped isometric contractions of the knee extensors, and MRI was used to determine tendon cross-sectional area (CSA) and signal intensity. At peak force, patellar tendon deformation, stress, and strain were 13 ( P = 0.05), 19, and 12% less in old compared with young ( P < 0.05). Additionally, deformation, stiffness, stress, CSA, and length were 18, 35, 41, 28, and 11% greater ( P < 0.05), respectively, in men compared with women. After normalization of mechanical properties to a common force, no age differences were apparent; however, stress and strain were 26 and 22% higher, respectively, in women compared with men ( P < 0.05). CSA and signal intensity decreased 12 and 24%, respectively, with aging ( P < 0.05) in the midregion of the tendon. These data suggest that differences in patellar tendon in vivo mechanical properties with aging are more related to force output rather than an age effect. In contrast, the decrease in signal intensity indirectly suggests that the internal milieu of the tendon is altered with aging; however, the physiological and functional consequence of this finding requires further study.

scholarly journals Effects of Residual Stress, Axial Stretch, and Circumferential Shrinkage on Coronary Plaque Stress and Strain Calculations: A Modeling Study Using IVUS-Based Near-Idealized Geometries

2016 ◽  
Vol 139 (1) ◽  
Author(s):  
Liang Wang ◽  
Jian Zhu ◽  
Habib Samady ◽  
David Monoly ◽  
Jie Zheng ◽  
...  
Keyword(s):  
Residual Stress ◽  
Coronary Plaque ◽  
Model Construction ◽  
Patient Specific ◽  
Stress And Strain ◽  
Stress Strain ◽  
Axial Stretch ◽  
Stress Increase ◽  
Specific Material

Accurate stress and strain calculations are important for plaque progression and vulnerability assessment. Models based on in vivo data often need to form geometries with zero-stress/strain conditions. The goal of this paper is to use IVUS-based near-idealized geometries and introduce a three-step model construction process to include residual stress, axial shrinkage, and circumferential shrinkage and investigate their impacts on stress and strain calculations. In Vivo intravascular ultrasound (IVUS) data of human coronary were acquired for model construction. In Vivo IVUS movie data were acquired and used to determine patient-specific material parameter values. A three-step modeling procedure was used to make our model: (a) wrap the zero-stress vessel sector to obtain the residual stress; (b) stretch the vessel axially to its length in vivo; and (c) pressurize the vessel to recover its in vivo geometry. Eight models were constructed for our investigation. Wrapping led to reduced lumen and cap stress and increased out boundary stress. The model with axial stretch, circumferential shrink, but no wrapping overestimated lumen and cap stress by 182% and 448%, respectively. The model with wrapping, circumferential shrink, but no axial stretch predicted average lumen stress and cap stress as 0.76 kPa and −15 kPa. The same model with 10% axial stretch had 42.53 kPa lumen stress and 29.0 kPa cap stress, respectively. Skipping circumferential shrinkage leads to overexpansion of the vessel and incorrect stress/strain calculations. Vessel stiffness increase (100%) leads to 75% lumen stress increase and 102% cap stress increase.

scholarly journals mRNA-Driven Generation of Transgene-Free Neural Stem Cells from Human Urine-Derived Cells

Cells ◽  
2019 ◽  
Vol 8 (9) ◽  
pp. 1043 ◽  
Author(s):  
Phil Jun Kang ◽  
Daryeon Son ◽  
Tae Hee Ko ◽  
Wonjun Hong ◽  
Wonjin Yun ◽  
...  
Keyword(s):  
Stem Cells ◽  
Neural Stem Cells ◽  
Human Urine ◽  
Neurological Disorders ◽  
Therapeutic Potential ◽  
Embryonic Stem ◽  
Global Gene Expression ◽  
Patient Specific ◽  
Human Neural Stem Cells

Human neural stem cells (NSCs) hold enormous promise for neurological disorders, typically requiring their expandable and differentiable properties for regeneration of damaged neural tissues. Despite the therapeutic potential of induced NSCs (iNSCs), a major challenge for clinical feasibility is the presence of integrated transgenes in the host genome, contributing to the risk for undesired genotoxicity and tumorigenesis. Here, we describe the advanced transgene-free generation of iNSCs from human urine-derived cells (HUCs) by combining a cocktail of defined small molecules with self-replicable mRNA delivery. The established iNSCs were completely transgene-free in their cytosol and genome and further resembled human embryonic stem cell-derived NSCs in the morphology, biological characteristics, global gene expression, and potential to differentiate into functional neurons, astrocytes, and oligodendrocytes. Moreover, iNSC colonies were observed within eight days under optimized conditions, and no teratomas formed in vivo, implying the absence of pluripotent cells. This study proposes an approach to generate transplantable iNSCs that can be broadly applied for neurological disorders in a safe, efficient, and patient-specific manner.

An experimental method for evaluating constitutive models of myocardium in in vivo hearts

1994 ◽  
Vol 267 (2) ◽  
pp. H853-H863 ◽  
Author(s):  
L. L. Creswell ◽  
M. J. Moulton ◽  
S. G. Wyers ◽  
J. S. Pirolo ◽  
D. S. Fishman ◽  
...  
Keyword(s):  
Experimental Method ◽  
Diastolic Pressure ◽  
Constitutive Models ◽  
Fe Analysis ◽  
Small Displacement ◽  
Ventricular Wall ◽  
Canine Heart ◽  
Unknown Parameters ◽  
Tissue Tagging

A new experimental method for the evaluation of myocardial constitutive models combines magnetic resonance (MR) radiofrequency (RF) tissue-tagging techniques with iterative two-dimensional (2-D) nonlinear finite element (FE) analysis. For demonstration, a nonlinear isotropic constitutive model for passive diastolic expansion in the in vivo canine heart is evaluated. A 2-D early diastolic FE mesh was constructed with loading parameters for the ventricular chambers taken from mean early diastolic-to-late diastolic pressure changes measured during MR imaging. FE solution was performed for regional, intramyocardial ventricular wall strains using small-strain, small-displacement theory. Corresponding regional ventricular wall strains were computed independently using MR images that incorporated RF tissue tagging. Two unknown parameters were determined for an exponential strain energy function that maximized agreement between observed (from MR) and predicted (from FE analysis) regional wall strains. Extension of this methodology will provide a framework in which to evaluate the quality of myocardial constitutive models of arbitrary complexity on a regional basis.

Design, Fabrication, and Accuracy of a Novel Noncovering Lock-Mechanism Bilateral Patient-Specific Drill Guide Template for Nondeformed and Deformed Thoracic Spines

2021 ◽  
pp. 155633162199633
Author(s):  
Mehran Ashouri-Sanjani ◽  
Shima Mohammadi-Moghadam ◽  
Parisa Azimi ◽  
Navid Arjmand
Keyword(s):  
Thoracic Spine ◽  
Sagittal Plane ◽  
Ct Scanning ◽  
Entry Point ◽  
In Vivo Studies ◽  
Patient Specific ◽  
Plane Angle ◽  
Severe Scoliosis ◽  
3D Printed

Background: Pedicle screw (PS) placement has been widely used in fusion surgeries on the thoracic spine. Achieving cost-effective yet accurate placements through nonradiation techniques remains challenging. Questions/Purposes: Novel noncovering lock-mechanism bilateral vertebra-specific drill guides for PS placement were designed/fabricated, and their accuracy for both nondeformed and deformed thoracic spines was tested. Methods: One nondeformed and 1 severe scoliosis human thoracic spine underwent computed tomographic (CT) scanning, and 2 identical proportions of each were 3-dimensional (3D) printed. Pedicle-specific optimal (no perforation) drilling trajectories were determined on the CT images based on the entry point/orientation/diameter/length of each PS. Vertebra-specific templates were designed and 3D printed, assuring minimal yet firm contacts with the vertebrae through a noncovering lock mechanism. One model of each patient was drilled using the freehand and one using the template guides (96 pedicle drillings). Postoperative CT scans from the models with the inserted PSs were obtained and superimposed on the preoperative planned models to evaluate deviations of the PSs. Results: All templates fitted their corresponding vertebra during the simulated operations. As compared with the freehand approach, PS placement deviations from their preplanned positions were significantly reduced: for the nonscoliosis model, from 2.4 to 0.9 mm for the entry point, 5.0° to 3.3° for the transverse plane angle, 7.1° to 2.2° for the sagittal plane angle, and 8.5° to 4.1° for the 3D angle, improving the success rate from 71.7% to 93.5%. Conclusions: These guides are valuable, as the accurate PS trajectory could be customized preoperatively to match the patients’ unique anatomy. In vivo studies will be required to validate this approach.

scholarly journals Evaluation of Bone–Implant Interface Stress and Strain Using Heterogeneous Mandibular Bone Properties Based on Different Empirical Correlations

2021 ◽  
Author(s):  
Mostafa Omran Hussein ◽  
Mohammed Suliman Alruthea
Keyword(s):  
Finite Element ◽  
Group Iv ◽  
Von Mises Stress ◽  
Patient Specific ◽  
Dental Arch ◽  
Stress And Strain ◽  
Bone Implant ◽  
Bone Properties ◽  
Group I ◽  
Von Mises

Abstract Objective The purpose of this study was to compare methods used for calculating heterogeneous patient-specific bone properties used in finite element analysis (FEA), in the field of implant dentistry, with the method based on homogenous bone properties. Materials and Methods In this study, three-dimensional (3D) computed tomography data of an edentulous patient were processed to create a finite element model, and five identical 3D implant models were created and distributed throughout the dental arch. Based on the calculation methods used for bone material assignment, four groups—groups I to IV—were defined. Groups I to III relied on heterogeneous bone property assignment based on different equations, whereas group IV relied on homogenous bone properties. Finally, 150 N vertical and 60-degree-inclined forces were applied at the top of the implant abutments to calculate the von Mises stress and strain. Results Groups I and II presented the highest stress and strain values, respectively. Based on the implant location, differences were observed between the stress values of group I, II, and III compared with group IV; however, no clear order was noted. Accordingly, variable von Mises stress and strain reactions at the bone–implant interface were observed among the heterogeneous bone property groups when compared with the homogenous property group results at the same implant positions. Conclusion Although the use of heterogeneous bone properties as material assignments in FEA studies seem promising for patient-specific analysis, the variations between their results raise doubts about their reliability. The results were influenced by implants’ locations leading to misleading clinical simulations.

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