A mathematical model of myocardial perfusion based on the lattice Boltzmann method (LBM) is proposed and its applicability is investigated in both healthy and diseased cases. The myocardium is conceptualized as a porous material in which the transport and mass transfer of a contrast agent in blood flow is studied. The results of myocardial perfusion obtained using LBM in 1D and 2D are confronted with previously reported results in the literature and the results obtained using the mixed-hybrid finite element method. Since LBM is not suitable for simulating flow in heterogeneous porous media, a simplified and computationally efficient 1D-analog approach to 2D diseased case is proposed and its applicability discussed.

• MeSH
• analýza metodou konečných prvků * MeSH
• kontrastní látky MeSH
• koronární cirkulace fyziologie   MeSH
• lidé MeSH
• modely kardiovaskulární * MeSH
• počítačová simulace MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH

Cíl: Zhodnotit kvalitativně použitelnost matematického modelu proudění prozobrazení toku v bifurkaci aorty ošetřené stenty. Metodika: Bylo provedeno devět vyšetření bifurkace aorty sekvencí 4D Flow.Vyšetřeni byli pacienti bez stentů, pacienti se stentem v jedné a pacienti sestenty v obou větvích bifurkace. Ze získaných dat o průtoku byla připravenavizualizace rychlostního pole. Na základě segmentace bifurkace aorty anaměřených dat o průtoku byla provedena simulace proudění, včetně oblastí, kdenebylo možné průtok naměřit kvůli artefaktům. Měřené a simulované rychlostnípole bylo porovnáno vizuálně. Výsledky: U pacientů bez stentů simulovaný tok přispěl k odstranění malýchnepřesností v měřeném poli. U pacientů se stenty byla simulovaná datakonzistentnější než měřená a poskytovala navíc obrázek i o situaci vestentech. Diskuse: Simulované rychlostní pole musí být z podstaty konzistentní sfyzikálními zákony, čímž umožňuje korekci měřených dat v místech, kde měřeníselhává. V závislosti na přesnosti segmentace cév může simulace i poskytnout novou diagnostickou informaci. Získané výsledky jsou ovšem pouzekvalitativní a bude je třeba ověřit kvantitativně. Závěr: Matematický model proudění může pomoci kvantitativně zhodnotit průtok vmístech cévy ošetřených stenty, kde přímé měření proudění krve magnetickourezonancí selhává.

Aim: The aim of the article is to qualitatively assess the usability of a mathematical flow model for visualizing the flow in aortic bifurcation treated with stents. Methodology: Nine examinations of aortic bifurcations were conducted using a 4D Flow sequence. Patients without stents, patients with a stent in one branch, and patients with stents in both branches of the aortic bifurcation were examined. 4D Flow data were used to prepare a visualization of the velocity field. Flow simulations were performed based on the segmented bifurcation and measured flow data, including areas where flow measurements were affected by artifacts. Measured and simulated velocity fields were visually compared. Results: For patients without stents, the simulated flow contributed to eliminating small inaccuracies in the measured field. In patients with stents, the simulated data were more consistent than the measured data and provided additional insight into the situation within the stents. Discussion: Simulated velocity fields must inherently adhere to the laws of physics, allowing for the correction of measured data in regions where measurements are compromised. Depending on the accuracy of the segmentation, it may also offer new diagnostic information. However, the obtained results are solely qualitative and will need quantitative validation. Conclusion: The mathematical flow model can aid in quantitative assessment of flow in the vascular locations treated with stents where the direct MR measurement of blood flow fails.

OBJECTIVE: The accuracy of phase-contrast magnetic resonance imaging (PC-MRI) measurement is investigated using a computational fluid dynamics (CFD) model with the objective to determine the magnitude of the flow underestimation due to turbulence behind a narrowed valve in a phantom experiment. MATERIALS AND METHODS: An acrylic stationary flow phantom is used with three insertable plates mimicking aortic valvular stenoses of varying degrees. Positive and negative horizontal fluxes are measured at equidistant slices using standard PC-MRI sequences by 1.5T and 3T systems. The CFD model is based on the 3D lattice Boltzmann method (LBM). The experimental and simulated data are compared using the Bland-Altman-derived limits of agreement. Based on the LBM results, the turbulence is quantified and confronted with the level of flow underestimation. RESULTS: LBM gives comparable results to PC-MRI for valves up to moderate stenosis on both field strengths. The flow magnitude through a severely stenotic valve was underestimated due to signal void in the regions of turbulent flow behind the valve, consistently with the level of quantified turbulence intensity. DISCUSSION: Flow measured by PC-MRI is affected by noise and turbulence. LBM can simulate turbulent flow efficiently and accurately, it has therefore the potential to improve clinical interpretation of PC-MRI.

• MeSH
• aortální chlopeň * MeSH
• aortální stenóza * MeSH
• fantomy radiodiagnostické MeSH
• lidé MeSH
• magnetická rezonanční tomografie MeSH
• rychlost toku krve MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH

This study presents a combined experimental and numerical investigation of fiber transport and deposition in a realistic model of the female respiratory tract, extending to the seventh generation of branching. Numerical simulations were performed using the Euler-Lagrange Euler-Rotation (ELER) method, an efficient alternative to conventional Finite Volume Methods that benefits from explicit formulation and vast scalability, enabling fast parallelization on high-performance clusters. The ELER method was coupled with the Lattice Boltzmann Method (LBM) to simulate fiber dynamics under a realistic inspiratory flow profile. Experimental validation was conducted using an identical physical airway replica. The results demonstrated good agreement between simulations and experiments in the upper airways and trachea, with some discrepancies in the bifurcations, likely owing to the challenges of modeling complex turbulent flow with ELER. This method is more accurate than corresponding effective diameter simulations. Deposition patterns were analyzed as a function of fiber dimensions, revealing higher accuracy of the ELER method for smaller particles and confirming the tendency of higher aspect ratio fibers to penetrate deeper into the lungs. The orientation-dependent deposition mechanism was deployed, underscoring the importance of solving the actual orientations of the fibers. While advancing our understanding of fiber transport in female airways, the findings also reveal limitations in current numerical techniques, particularly in bifurcations. This study emphasizes the distinct behavior of fibrous versus spherical particles, with fibers exhibiting a greater propensity to reach deeper lung regions, which has significant implications for inhalation toxicology and drug delivery.

• MeSH
• aplikace inhalační MeSH
• biologické modely * MeSH
• dýchací soustava * MeSH
• lidé MeSH
• plíce MeSH
• počítačová simulace MeSH
• trachea * fyziologie   MeSH
• Check Tag
• lidé MeSH
• ženské pohlaví MeSH
• Publikační typ
• časopisecké články MeSH

• MeSH
• fyzikální jevy MeSH
• magnetická rezonanční tomografie MeSH

• Konspekt
• Patologie. Klinická medicína
• NLK Obory
• radiologie, nukleární medicína a zobrazovací metody
• NLK Publikační typ
• kolektivní monografie