Impact of Patient-Specific Inflow Velocity Profile on Hemodynamics of the Thoracic Aorta

2017 ◽  
Vol 140 (1) ◽  
Author(s):  
Pouya Youssefi ◽  
Alberto Gomez ◽  
Christopher Arthurs ◽  
Rajan Sharma ◽  
Marjan Jahangiri ◽  
...  
Keyword(s):  
Aortic Valve ◽  
Thoracic Aorta ◽  
Complex Structure ◽  
Three Dimensional ◽  
Velocity Profiles ◽  
Patient Specific ◽  
Inflow Velocity ◽  
Valvular Stenosis ◽  
Computational Fluid Dynamics Cfd ◽  
Magnetic Resonance Imaging Mri

Computational fluid dynamics (CFD) provides a noninvasive method to functionally assess aortic hemodynamics. The thoracic aorta has an anatomically complex inlet comprising of the aortic valve and root, which is highly prone to different morphologies and pathologies. We investigated the effect of using patient-specific (PS) inflow velocity profiles compared to idealized profiles based on the patient's flow waveform. A healthy 31 yo with a normally functioning tricuspid aortic valve (subject A), and a 52 yo with a bicuspid aortic valve (BAV), aortic valvular stenosis, and dilated ascending aorta (subject B) were studied. Subjects underwent MR angiography to image and reconstruct three-dimensional (3D) geometric models of the thoracic aorta. Flow-magnetic resonance imaging (MRI) was acquired above the aortic valve and used to extract the patient-specific velocity profiles. Subject B's eccentric asymmetrical inflow profile led to highly complex velocity patterns, which were not replicated by the idealized velocity profiles. Despite having identical flow rates, the idealized inflow profiles displayed significantly different peak and radial velocities. Subject A's results showed some similarity between PS and parabolic inflow profiles; however, other parameters such as Flowasymmetry were significantly different. Idealized inflow velocity profiles significantly alter velocity patterns and produce inaccurate hemodynamic assessments in the thoracic aorta. The complex structure of the aortic valve and its predisposition to pathological change means the inflow into the thoracic aorta can be highly variable. CFD analysis of the thoracic aorta needs to utilize fully PS inflow boundary conditions in order to produce truly meaningful results.

Simulation of personalised haemodynamics by various mounting positions of a prosthetic valve using computational fluid dynamics

2019 ◽  
Vol 64 (2) ◽  
pp. 147-156 ◽  
Author(s):  
Markus Bongert ◽  
Marius Geller ◽  
Werner Pennekamp ◽  
Volkmar Nicolas
Keyword(s):  
Blood Flow ◽  
Aortic Valve ◽  
Three Dimensional ◽  
Maximum Velocity ◽  
Heart Valve Disease ◽  
Patient Specific ◽  
Opening Angle ◽  
The European Union ◽  
Prosthetic Valves ◽  
Magnetic Resonance Imaging Mri

Abstract Diseases of the cardiovascular system account for nearly 42% of all deaths in the European Union. In Germany, approximately 12,000 patients receive surgical replacement of the aortic valve due to heart valve disease alone each year. A three-dimensional (3D) numerical model based on patient-specific anatomy derived from four-dimensional (4D) magnetic resonance imaging (MRI) data was developed to investigate preoperatively the flow-induced impact of mounting positions of aortic prosthetic valves to select the best orientation for individual patients. Systematic steady-state analysis of blood flow for different rotational mounting positions of the valve is only possible using a virtual patient model. A maximum velocity of 1 m/s was used as an inlet boundary condition, because the opening angle of the valve is at its largest at this velocity. For a comparative serial examination, it is important to define the standardised general requirements to avoid impacts other than the rotated implantation of the prosthetic aortic valve. In this study, a uniform velocity profile at the inlet for the inflow of the aortic valve and the real aortic anatomy were chosen for all simulations. An iterative process, with the weighted parameters flow resistance (1), shear stress (2) and velocity (3), was necessary to determine the best rotated orientation. Blood flow was optimal at a 45° rotation from the standard implantation orientation, which will offer a supply to the coronary arteries.

scholarly journals Patient-Specific Aortic Phantom With Tunable Compliance

2019 ◽  
Vol 2 (4) ◽  
Author(s):  
Antonio Gallarello ◽  
Andrea Palombi ◽  
Giacomo Annio ◽  
Shervanthi Homer-Vanniasinkam ◽  
Elena De Momi ◽  
...  
Keyword(s):  
Aortic Arch ◽  
Computational Models ◽  
Three Dimensional ◽  
Complex Interventions ◽  
Patient Specific ◽  
Arch Model ◽  
Magnetic Resonance Imaging Mri ◽  
Variable Wall ◽  
Silicone Model

Abstract Validation of computational models using in vitro phantoms is a nontrivial task, especially in the replication of the mechanical properties of the vessel walls, which varies with age and pathophysiological state. In this paper, we present a novel aortic phantom reconstructed from patient-specific data with variable wall compliance that can be tuned without recreating the phantom. The three-dimensional (3D) geometry of an aortic arch was retrieved from a computed tomography angiography scan. A rubber-like silicone phantom was manufactured and connected to a compliance chamber in order to tune its compliance. A lumped resistance was also coupled with the system. The compliance of the aortic arch model was validated using the Young's modulus and characterized further with respect to clinically relevant indicators. The silicone model demonstrates that compliance can be finely tuned with this system under pulsatile flow conditions. The phantom replicated values of compliance in the physiological range. Both, the pressure curves and the asymmetrical behavior of the expansion, are in agreement with the literature. This novel design approach allows obtaining for the first time a phantom with tunable compliance. Vascular phantoms designed and developed with the methodology proposed in this paper have high potential to be used in diverse conditions. Applications include training of physicians, pre-operative trials for complex interventions, testing of medical devices for cardiovascular diseases (CVDs), and comparative Magnetic-resonance-imaging (MRI)-based computational studies.

scholarly journals Meningioma Segmentation in T1-Weighted MRI Leveraging Global Context and Attention Mechanisms

2021 ◽  
Vol 1 ◽  
Author(s):  
David Bouget ◽  
André Pedersen ◽  
Sayied Abdol Mohieb Hosainey ◽  
Ole Solheim ◽  
Ingerid Reinertsen
Keyword(s):  
Three Dimensional ◽  
Specific Treatment ◽  
Primary Brain Tumor ◽  
University Hospital ◽  
Patient Specific ◽  
Entire Volume ◽  
Global Context ◽  
Multi Scale ◽  
Magnetic Resonance Imaging Mri ◽  
The Impact

Purpose: Meningiomas are the most common type of primary brain tumor, accounting for ~30% of all brain tumors. A substantial number of these tumors are never surgically removed but rather monitored over time. Automatic and precise meningioma segmentation is, therefore, beneficial to enable reliable growth estimation and patient-specific treatment planning.Methods: In this study, we propose the inclusion of attention mechanisms on top of a U-Net architecture used as backbone: (i) Attention-gated U-Net (AGUNet) and (ii) Dual Attention U-Net (DAUNet), using a three-dimensional (3D) magnetic resonance imaging (MRI) volume as input. Attention has the potential to leverage the global context and identify features' relationships across the entire volume. To limit spatial resolution degradation and loss of detail inherent to encoder–decoder architectures, we studied the impact of multi-scale input and deep supervision components. The proposed architectures are trainable end-to-end and each concept can be seamlessly disabled for ablation studies.Results: The validation studies were performed using a five-fold cross-validation over 600 T1-weighted MRI volumes from St. Olavs Hospital, Trondheim University Hospital, Norway. Models were evaluated based on segmentation, detection, and speed performances, and results are reported patient-wise after averaging across all folds. For the best-performing architecture, an average Dice score of 81.6% was reached for an F1-score of 95.6%. With an almost perfect precision of 98%, meningiomas smaller than 3 ml were occasionally missed hence reaching an overall recall of 93%.Conclusion: Leveraging global context from a 3D MRI volume provided the best performances, even if the native volume resolution could not be processed directly due to current GPU memory limitations. Overall, near-perfect detection was achieved for meningiomas larger than 3 ml, which is relevant for clinical use. In the future, the use of multi-scale designs and refinement networks should be further investigated. A larger number of cases with meningiomas below 3 ml might also be needed to improve the performance for the smallest tumors.

scholarly journals The Impact of Cardiac Motion on Aortic Valve Flow Used in Computational Simulations of the Thoracic Aorta

2016 ◽  
Vol 138 (9) ◽  
Author(s):  
David C. Wendell ◽  
Margaret M. Samyn ◽  
Joseph R. Cava ◽  
Mary M. Krolikowski ◽  
John F. LaDisa
Keyword(s):  
Blood Flow ◽  
Aortic Valve ◽  
Coarctation Of The Aorta ◽  
Outer Wall ◽  
Cardiac Motion ◽  
Patient Specific ◽  
Flow Measurements ◽  
Computational Fluid Dynamics Cfd ◽  
Blood Flow Measurements ◽  
The Impact

Advancements in image-based computational modeling are producing increasingly more realistic representations of vasculature and hemodynamics, but so far have not compensated for cardiac motion when imposing inflow boundary conditions. The effect of cardiac motion on aortic flow is important when assessing sequelae in this region including coarctation of the aorta (CoA) or regurgitant fraction. The objective of this investigation was to develop a method to assess and correct for the influence of cardiac motion on blood flow measurements through the aortic valve (AoV) and to determine its impact on patient-specific local hemodynamics quantified by computational fluid dynamics (CFD). A motion-compensated inflow waveform was imposed into the CFD model of a patient with repaired CoA that accounted for the distance traveled by the basal plane during the cardiac cycle. Time-averaged wall shear stress (TAWSS) and turbulent kinetic energy (TKE) values were compared with CFD results of the same patient using the original waveform. Cardiac motion resulted in underestimation of flow during systole and overestimation during diastole. Influences of inflow waveforms on TAWSS were greatest along the outer wall of the ascending aorta (AscAo) (∼30 dyn/cm2). Differences in TAWSS were more pronounced than those from the model creation or mesh dependence aspects of CFD. TKE was slightly higher for the motion-compensated waveform throughout the aortic arch. These results suggest that accounting for cardiac motion when quantifying blood flow through the AoV can lead to different conclusions for hemodynamic indices, which may be important if these results are ultimately used to predict patient outcomes.

scholarly journals A proof-of-concept study of the in-vivo validation of a computational fluid dynamics model of personalized radioembolization

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Raúl Antón ◽  
Javier Antoñana ◽  
Jorge Aramburu ◽  
Ana Ezponda ◽  
Elena Prieto ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Three Dimensional ◽  
Patient Specific ◽  
Percentage Points ◽  
Pet Ct ◽  
Voxel Dosimetry ◽  
Computational Fluid Dynamics Cfd ◽  
Intraarterial Therapy

AbstractRadioembolization (RE) with yttrium-90 (90Y) microspheres, a transcatheter intraarterial therapy for patients with liver cancer, can be modeled computationally. The purpose of this work was to correlate the results obtained with this methodology using in vivo data, so that this computational tool could be used for the optimization of the RE procedure. The hepatic artery three-dimensional (3D) hemodynamics and microsphere distribution during RE were modeled for six 90Y-loaded microsphere infusions in three patients with hepatocellular carcinoma using a commercially available computational fluid dynamics (CFD) software package. The model was built based on in vivo data acquired during the pretreatment stage. The results of the simulations were compared with the in vivo distribution assessed by 90Y PET/CT. Specifically, the microsphere distribution predicted was compared with the actual 90Y activity per liver segment with a commercially available 3D-voxel dosimetry software (PLANET Dose, DOSIsoft). The average difference between the CFD-based and the PET/CT-based activity distribution was 2.36 percentage points for Patient 1, 3.51 percentage points for Patient 2 and 2.02 percentage points for Patient 3. These results suggest that CFD simulations may help to predict 90Y-microsphere distribution after RE and could be used to optimize the RE procedure on a patient-specific basis.

scholarly journals Simulated Prosthesis Overlay for Patient-Specific Planning of Transcatheter Aortic Valve Implantation Procedures

2015 ◽  
Vol 10 (5) ◽  
pp. 314-322 ◽  
Author(s):  
Simon H. Sündermann ◽  
Michael Gessat ◽  
Willibald Maier ◽  
Jörg Kempfert ◽  
Thomas Frauenfelder ◽  
...  
Keyword(s):  
Aortic Valve ◽  
Transcatheter Aortic Valve Implantation ◽  
Pacemaker Implantation ◽  
Three Dimensional ◽  
Patient Data ◽  
Equal Size ◽  
Patient Specific ◽  
Transcatheter Aortic Valve ◽  
Aortic Valve Implantation ◽  
Valve Implantation

Objective We tested the hypothesis that simulated three-dimensional prosthesis overlay procedure planning may support valve selection in transcatheter aortic valve implantation (TAVI) procedures. Methods Preoperative multidimensional computed tomography (MDCT) data sets from 81 consecutive TAVI patients were included in the study. A planning tool was developed, which semiautomatically creates a three-dimensional model of the aortic root from these data. Three-dimensional templates of the commonly used TAVI implants are spatially registered with the patient data and presented as graphic overlay. Fourteen physicians used the tool to perform retrospective planning of TAVI procedures. Results of prosthesis sizing were compared with the prosthesis size used in the actually performed procedure, and the patients were accordingly divided into three groups: those with equal size (concordance with retrospective planning), oversizing (retrospective planning of a smaller prosthesis), and undersizing (retrospective planning of a larger prosthesis). Results In the oversizing group, 85% of the patients had new pacemaker implantation. In the undersizing group, in 66%, at least mild paravalvular leakage was observed (greater than grade 1 in one third of the cases). In 46% of the patients in the equal-size group, neither of these complications was observed. Conclusions Three-dimensional prosthesis overlay in MDCT-derived patient data for patient-specific planning of TAVI procedures is feasible. It may improve valve selection compared with two-dimensional MDCT planning and thus yield better outcomes.

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