Rivas-Nieto, A. (Alejandro)
- Publications
- item.page.relationships.isContributorAdvisorOfPublication
- item.page.relationships.isContributorOfPublication
8 results
Search Results
Now showing 1 - 8 of 8
- Mathematical modeling and numerical simulation of surfactant delivery within a physical model of the neonatal trachea for different aerosol characteristics(Taylor & Francis, 2017-03) Murgia-Esteve, X.(Xabier); Goikoetxea-Miranda, E. (Estibalitz); Rivas-Nieto, A. (Alejandro); Antón-Remírez, R. (Raúl)Surfactant aerosol delivery in conjunction with a noninvasive respiratory support holds the potential to treat neonatal respiratory distress syndrome in a safe manner. The objective of the present study was to gain knowledge in order to optimize the geometry of an intracorporeal inhalation catheter and improve surfactant aerosol delivery effectiveness in neonates. Initially, a mathematical model capable of predicting the aerosol flow generated by this inhalation catheter within a physical model of the neonatal trachea was implemented and validated. Subsequently, a numerical study was performed to analyze the effect of the aerosol liquid droplet size and mass flow rate on surfactant delivery and on the required aerosolization time period. Experimental validation of the mathematical model showed a close prediction of the air axial velocity at the distal end of the physical model, with an absolute error between 0.01 and 0.15 m/s. Furthermore, an admissible absolute error between 0.2 and 2 mm was attained in the prediction of the aerosol mean aerodynamic diameter and mass median aerodynamic diameter in this region. The numerical study highlighted the beneficial effects of generating an intracorporeal aerosol with a mass median aerodynamic diameter higher than 4 mm and a surfactant mass flow rate above 8.93 mg/s in order to obtain effective surfactant delivery in neonates with minimal airway manipulation.
- Computational particle–haemodynamics analysis of liver radioembolization pretreatment as an actual treatment surrogate(Willey, 2017-02) Aramburu-Montenegro, J. (Jorge); Sangro, B. (Bruno); Bilbao, J.I. (José I.); Ramos-González, J. (Juan Carlos); Rivas-Nieto, A. (Alejandro); Antón-Remírez, R. (Raúl)Liver radioembolization (RE) is a treatment option for patients with unresectable and chemorefractory primary and metastatic liver tumours. RE consists of intra-arterially administering via catheter radioactive microspheres that locally attack the tumours, sparing healthy tissue. Prior to RE, the standard practice is to conduct a treatment-mimicking pretreatment assessment via the infusion of Tc-99m-labelled macroaggregated albumin microparticles. The usefulness of this pretreatment has been debated in the literature, and thus, the aim of the present study is to shed light on this issue by numerically simulating the liver RE pretreatment and actual treatment particle-haemodynamics in a patient-specific hepatic artery under two different literature-based cancer scenarios and two different placements of a realistic end-hole microcatheter in the proper hepatic artery. The parameters that are analysed are the following: microagent quantity and size (accounting for RE pretreatment and treatment),...
- The role of angled-tip microcatheter and microsphere injection velocity in liver radioembolization: A computational particle–hemodynamics study.(Wiley, 2017-12) Aramburu-Montenegro, J. (Jorge); Sangro, B. (Bruno); Bilbao, J.I. (José I.); Ramos-González, J. (Juan Carlos); Rivas-Nieto, A. (Alejandro); Antón-Remírez, R. (Raúl)Liver radioembolization is a promising treatment option for combating liver tumors. It is performed by placing a microcatheter in the hepatic artery and administering radiation-emitting microspheres through the arterial bloodstream so that they get lodged in the tumoral bed. In avoiding nontarget radiation, the standard practice is to conduct a pretreatment, in which the microcatheter location and injection velocity are decided. However, between pretreatment and actual treatment, some of the parameters that influence the particle distribution in the liver can vary, resulting in radiation-induced complications. The present study aims to analyze the influence of a commercially available microcatheter with an angled tip and particle injection velocity in terms of segment-to-segment particle distribution. Specifically, 4 tip orientations and 2 injection velocities are combined to yield a set of 8 numerical simulations of the particle-hemodynamics in a patient-specific truncated hepatic artery. For each simulation, 4 cardiac pulses are simulated. Particles are injected during the first cycle, and the remaining pulses enable the majority of the injected particles to exit the computational domain. Results indicate that, in terms of injection velocity, particles are more spread out in the cross-sectional lumen areas as the injection velocity increases. The tip's orientation also plays a role because it influences the near-tip hemodynamics, therefore altering the particle travel through the hepatic artery. However, results suggest that particle distribution tries to match the blood flow split, therefore particle injection velocity and microcatheter tip orientation playing a minor role in segment-to-segment particle distribution.
- Experimental study of the influence of operational and geometric variables on the powders produced by close-coupled gas atomisation.(ELSEVIER, 2021-02) Urionabarrenetxea, E. (Ernesto); Martín-García, J.M. (José Manuel); Avello-Iturriagagoitia, A. (Alejo); Rivas-Nieto, A. (Alejandro)The effect of several operational and geometric variables on the particle size distribution of powders produced by close-coupled gas atomisation is analysed from a total of 66 experiments. Powders of three pure metals (copper, tin and iron) and two alloys (bronze Cu-15 wt% Sn and stainless steel SS 316 L) have been produced. Nitrogen, argon and helium were used as atomising gases. It is shown that the gas-to-metal ratio of volume flow rates (GMRV) is more relevant than the ratio of mass flow rates (GMR) in order to analyse the effect of atomisation variables on the particle size. Kishidaka's equation, originally proposed for water atomisation, is modified to predict the median particle size in gas atomisation. The accuracy of the new equation is compared with that of Lubanska, and Rao and Mehrotra. Kishidaka's modified empirical correlation is the most accurate in predicting the median particle size of the powders produced in this work. The morphology of the produced powders is studied by scanning electron microscopy (SEM) and it is observed that the melt superheat can play an important role in the aggregation of fine particles (< 10 mu m), which increases the fraction of large particles (> 100 mu m).
- Liver cancer arterial perfusion modelling and CFD boundary conditions methodology: a case study of the haemodynamics of a patient-specific hepatic artery in literature-based healthy and tumour-bearing liver scenarios(Willey, 2016-11) Aramburu-Montenegro, J. (Jorge); Sangro, B. (Bruno); Bilbao, J.I. (José I.); Ramos-González, J. (Juan Carlos); Rivas-Nieto, A. (Alejandro); Antón-Remírez, R. (Raúl)Some of the latest treatments for unresectable liver malignancies (primary or metastatic tumours), which include bland embolisation, chemoembolisation, and radioembolisation, among others, take advantage of the increased arterial blood supply to the tumours to locally attack them. A better understanding of the factors that influence this transport may help improve the therapeutic procedures by taking advantage of flow patterns or by designing catheters and infusion systems that result in the injected beads having increased access to the tumour vasculature. Computational analyses may help understand the haemodynamic patterns and embolic-microsphere transport through the hepatic arteries. In addition, physiological inflow and outflow boundary conditions are essential in order to reliably represent the blood flow through arteries. This study presents a liver cancer arterial perfusion model based on a literature review and derives boundary conditions for tumour-bearing liver-feeding hepatic arteries based on the arterial perfusion characteristics of normal and tumorous liver segment tissue masses and the hepatic artery branching configuration. Literature-based healthy and tumour-bearing realistic scenarios are created and haemodynamically analysed for the same patient-specific hepatic artery. As a result, this study provides boundary conditions for computational fluid dynamics simulations that will allow researchers to numerically study, for example, various intravascular devices used for liver disease intra-arterial treatments with different cancer scenarios.
- Modeling based on design of thermal management systems for vertical elevation applications powered by lithium-ion batteries(Elsevier, 2016-06) Martin-Martin, L. (Leire); Nieto, N. (Nerea); Gastelurrutia, J.(Jon); Gil, I. (Iñigo); Ramos-González, J. (Juan Carlos); Rivas-Nieto, A. (Alejandro)Environmental sustainability, more efficient use of energy, and active safety concepts are becoming important requirements for the actual elevation sector. In this context IK4-IKERLAN and ORONA have designed an auxiliary energy storage system (ESS) for a residential elevation application based on lithium-ion cells. Safety and specially lifetime are two of the main concerns surrounding this new technology, which is closely related to the cells operating behavior and temperature asymmetries in the complete ESS. Therefore, the temperature of the cells in battery packs (BPs) needs to be controlled in an efficient way. This paper describes the development of the thermal management system (TMS) designed for this application based on various Computational Fluid Dynamics (CFD) mathematical models. The accuracy of Transient model is validated by using a single module to compare the simulation temperature results with experimental measurements, with a maximum time-averaged temperature prediction error of 1.5 degrees C. The proposed design is validated as it fulfills the requirements for a wide operating window, with a maximum cell temperature of 39 degrees C and a thermal dispersion at system level below 3 degrees C for the worst tested case. A more realistic current profile is checked numerically in the worst ambient and operative conditions for different virtual design variants to propose improvements.
- Computational assessment of the effects of the catheter type on particle–hemodynamics during liver radioembolization(Elsevier, 2016-11) Aramburu-Montenegro, J. (Jorge); Sangro, B. (Bruno); Bilbao, J.I. (José I.); Ramos-González, J. (Juan Carlos); Rivas-Nieto, A. (Alejandro); Antón-Remírez, R. (Raúl)Radioembolization, which consist of the implantation of radioactive microspheres via intra-arterially placed microcatheter, is a safe and effective treatment for liver cancer. Nevertheless, radioembolizationrelated complications and side effects may arise, which are an active area of ongoing research. The catheter design has been claimed as an option in reducing these complications. In this paper, the influence of catheter type and location are investigated. The study was undertaken by numerically simulating the particle-hemodynamics in a patient-specific hepatic artery during liver radioembolization. The parameters modified were cancer scenario (30% liver involvement in the right lobe, 'scenario A', and in both lobes, 'scenario B'), catheter type (standard end-hole microcatheter, SMC, and antireflux catheter, ARC), and the location of the tip in the proper hepatic artery (in the straight part, 'inlet', and near the bifurcation, 'bifurcation'). Comparing ARC with SMC, the maximum and average (over segments) absolute difference in the percentage of particles that reached each segment were 19.62% and 9.06% when injecting near the inlet for scenario A; 3.54% and 1.07% injecting near the bifurcation for scenario A; and 18.31% and 11.85% injecting near the inlet for scenario B. It seems, therefore, that the location of the catheter tip in the artery is crucial in terms of particle distribution. Moreover, even though the near-tip blood flow was altered due to the presence of a catheter, the particle distribution matched the flow split if the distance between the injection point and the first bifurcation encountered enabled the alignment of particles with blood flow.
- On the importance of spiral-flow inflow boundary conditions when using idealized artery geometries in the analysis of liver radioembolization: A parametric study.(2020) Ortega, J. (Julio); Antón-Remírez, R. (Raúl); Ramos-González, J. (Juan Carlos); Rivas-Nieto, A. (Alejandro); Sanchez-Larraona, G. (Gorka); Sangro, B. (Bruno); Bilbao, J.I. (José I.); Aramburu-Montenegro, J. (Jorge)