OAR@UM Collection:

Computational assessment of the deposited power and the temperature increase around two coupled implanted leads inside a 1.5 T MRI scanner

Mon, 01 Jan 2024 00:00:00 GMT

Title: Computational assessment of the deposited power and the temperature increase around two coupled implanted leads inside a 1.5 T MRI scanner Authors: Tsanidis, George; Samaras, Theodoros Abstract: A specific method for the estimation of the induced power at the tip by an active implantable medical device (AIMD) during an MRI scan is not defined in ISO/TS 10974:2018 for the cases of devices with multiple leads or the presence of abandoned and retained leads, where coupling between two leads could take place. Therefore, the aim of this work is to evaluate a numerical method, similar to Tier 3 of ISO/TS 10974:2018, for the estimation of the deposited power at the tips of two coupled implanted leads. Specifically, the proposed methodology applies the same parameters as the standard Tier 3 process. However, these parameters are calculated for each implant in the presence of its neighbors in order to include the coupling between them. Numerical electromagnetic simulations were performed, in which a pair of generic implant leads was excited and placed at various positions relative to each other. The deposited power at the tips of the pair was analyzed based on the standard Tier 3 approach, and the results show that this could overestimate the induced power by more than 6 dB. Therefore, a modified Tier 3 numerical method for the estimation of the deposited power at their tips is proposed, which can produce a reliable calculation. This method was confirmed by evaluating various configurations of the two leads excited by orthogonal electrical fields, and also its uncertainty budget was developed. Finally, the method was repeated for different properties of the generic implants and the surrounding tissue, as well as for a pair of realistic implants and in vivo implantation trajectories.

Atmospheric new particle formation identifier using longitudinal global particle number size distribution data

Mon, 01 Jan 2024 00:00:00 GMT

Title: Atmospheric new particle formation identifier using longitudinal global particle number size distribution data Authors: Kecorius, Simonas; Madueño, Leizel; Lovric, Mario; Racic, Nikolina; Schwarz, Maximilian; Cyrys, Josef; Casquero-Vera, Juan Andrés; Alados-Arboledas, Lucas; Conil, Sébastien; Sciare, Jean; Ondracek, Jakub; Gannet Hallar, Anna; Gómez-Moreno, Francisco J.; Ellul, Raymond; Kristensson, Adam; Sorribas, Mar; Kalivitis, Nikolaos; Mihalopoulos, Nikolaos; Peters, Annette; Gini, Maria; Konstantinos, Konstantinos; Vratolis, Stergios; Jeongeun, Kim; Birmili, Wolfram; Bergmans, Benjamin; Nikolova, Nina; Dinoi, Adelaide; Contini, Daniele; Marinoni, Angela; Alastuey, Andres; Petäjä, Tuukka; Rodriguez, Sergio; Picard, David; Brem, Benjamin; Priestman, Max; Green, David C.; Beddows, David C. S.; Harrison, Roy M.; O’Dowd, Colin; Ceburnis, Darius; Hyvärinen, Antti; Henzing, Bas; Crumeyrolle, Suzanne; Putaud, Jean-Philippe; Laj, Paolo; Weinhold, Kay; Plauškaitė, Kristina; Byčenkienė, Steigvilė Abstract: Atmospheric new particle formation (NPF) is a naturally occurring phenomenon, during which high concentrations of sub-10 nm particles are created through gas to particle conversion. The NPF is observed in multiple environments around the world. Although it has observable influence onto annual total and ultrafine particle number concentrations (PNC and UFP, respectively), only limited epidemiological studies have investigated whether these particles are associated with adverse health effects. One plausible reason for this limitation may be related to the absence of NPF identifiers available in UFP and PNC data sets. Until recently, the regional NPF events were usually identified manually from particle number size distribution contour plots. Identification of NPF across multi-annual and multiple station data sets remained a tedious task. In this work, we introduce a regional NPF identifier, created using an automated, machine learning based algorithm. The regional NPF event tag was created for 65 measurement sites globally, covering the period from 1996 to 2023. The discussed data set can be used in future studies related to regional NPF.

EPOCHS paper V. The dependence of galaxy formation on galaxy structure at 𝓏 < 7 from 𝘑𝘞𝘚𝘛 observations

Mon, 01 Jan 2024 00:00:00 GMT

Title: EPOCHS paper V. The dependence of galaxy formation on galaxy structure at 𝓏 < 7 from 𝘑𝘞𝘚𝘛 observations Authors: Conselice, Christopher J.; Basham, Justin T. F.; Bettaney, Daniel O.; Ferreira, Leonardo; Adams, Nathan; Harvey, Thomas; Ormerod, Katherine; Caruana, Joseph; Bluck, Asa F. L.; Li, Qiong; Roper, William J.; Trussler, James; Irodotou, Dimitrios; Austin, Duncan Abstract: We measure the broad impact of galaxy structure on galaxy formation by examining the ongoing star formation and integrated star formation history as revealed through the stellar masses of galaxies at z < 7 based on JWST CEERS data from the Extended Groth Strip (EGS). Using the morphological catalog of 3965 visually classified JWST galaxies from Ferreira et al. (2023), we investigate the evolution of stars, and when they form, as a function of morphological type as well as galaxies classified as passive and starburst through spectral energy distributions. Although disc galaxies dominate the structures of galaxies at z < 7, we find that these discs are in general either ‘passive’, or on the main sequence of star formation, and do not contain a large population of starburst galaxies. We also find no significant correlation between morphological type and the star formation rate or colours of galaxies at z < 7. In fact, we find that the morphologically classified ‘spheroids’ tend to be blue and are not found to be predominately passive systems at z > 1.5. We also find that the stellar mass function for disc galaxies does not evolve significantly during this time, whereas other galaxy types, such as the peculiar population, evolve dramatically, declining at lower redshifts. This indicates that massive peculiars are more common at higher redshifts. We further find that up to z ∼ 7, the specific star formation rate (sSFR) does not vary with visual morphology, but strongly depends on stellar mass and internal galaxy mass density. This demonstrates that at early epochs galaxy assembly is a mass-driven, rather than a morphologically driven process. Quenching of star formation is therefore a mass-dominated process throughout the universe’s history, likely due to the presence of supermassive black holes.

Computational investigation of the factors that affect tangential electric fields along cardiac lead paths inside MRI birdcage coils

Mon, 01 Jan 2024 00:00:00 GMT

Title: Computational investigation of the factors that affect tangential electric fields along cardiac lead paths inside MRI birdcage coils Authors: Tsanidis, George; Samaras, Theodoros Abstract: The medical imaging of a patient with a cardiac implantable electronic device (CIED) inside a magnetic resonance imaging (MRI) scanner carries the risk of tissue heating at the tip of the implant lead. In this work, we numerically assessed the impact of various factors, namely the resonant frequency, the imaging position, the implant position inside the human body and the coil configuration, on the induced tangential electric field along 10,080 cardiac lead paths at 1140 different scanning scenarios. During this comparative process, a function was considered based on the induced electrical potential at the tip of the lead. The input power of each coil was adjusted to generate constant B1+RMS at the iso-center or to limit the global SAR to the values provided in the safety guidelines IEC 60601-33. The values of the function were higher for higher static field and longer coil lengths when assessing the cases of a constrained B1+RMS, and the trend was reversed considering the limiting SAR values. Moreover, the electric field was higher as the imaging landmark approached the thorax and the neck. It was also shown that both the choice regarding the insertion vein of the lead and the positioning of the implantable pulse generator (IPG) affected the induced tangential electric field along the paths. In particular, when the CIED lead was inserted into the left axillary vein instead of entering into the right subclavian vein, the electrical potential at the tip could be on average lower by 1.6 dB and 2.1 dB at 1.5 T and 3 T, respectively.