3.10 Tesis magíster

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Browsing 3.10 Tesis magíster by browse.metadata.categoria "Tecnología"

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    A critical analysis of Shuryak’s Predictive Radiocarcinogenesis Model
    (2024) Heumann Schröder, Nicolás Matthias; Sánchez Nieto, Beatriz; Espinoza Bornscheuer, Ignacio Guillermo; Pontificia Universidad Católica de Chile. Instituto de Física
    Objective: To critically analyze, simplify and implement a predictive radiocarcinogenesis model to estimate the risk of secondary cancer after RT which can effectively compare different radiotherapy treatment plans with the aim of having an additional element of information during the decision-making process for the best RT plan.Methodology: A Python software was developed that was able to implement the model proposed by Shuryak et al. (2009). Simplifications and minor corrections were made which allowed for more compactness and more efficient run times. The model was then reparametrized with newer data from the Surveillance, Epidemiology, and End Results Program (SEER) database and several epidemiological studies using Bayesian Inference. Uncertainty propagation studies were then conducted to understand their propagation better. Finally, the model with its new parameters was applied to a selection of prostate plans to determine if it could construct a risk hierarchy.Results: The model was successfully reparametrized with newer data. Although some parameters show significant deviation from Shuryak’s original parameters, they are mostly on the same order of magnitude, and the differences arise likely due to differences in fitted data and the fitting process itself. Shuryak’s model successfully built a risk hierarchy between prostate plans, although it deviated from the more simplistic linear non-threshold BEIR VII model. It was also possible to simplify some complex mathematical equations, both in general and for particular cases, allowing for easier implementation and more efficient run times.Conclusions: Shuryak’s model was successfully reparametrized and implemented, showing potential to become clinically applicable. However, more comparisons between the model’s result and epidemiological data must be made to evaluate its accuracy better, and more concise and complete second primary cancer studies must be used before the model is reliable enough for clinical decision-making.
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    Chemical sensor based on nitrogen-vacancy centers in diamond
    (2020) Santibáñez Cisternas, Vicente Andrés; Maze Ríos, Jerónimo; Pontificia Universidad Católica de Chile. Instituto de Física
    During the last decade, the nitrogen-vancancy (NV) center in diamond has emerged as a solid platform for nanoscale quantum sensing, within which is electrometry and magnetometry. Owing to the NV center high sensitivity and the fact that the diamond withstands adverse environmental conditions, a chemical sensor based on NV centers is a promising candidate for measurements during mining processes. Here, we use a microfluidic confocal microscope and a shallow-implanted diamond with different implantation spots, which are circular areas of 35 um diameter, to perform longitudinal spin relaxometry in the presence of sodium sulfate in aqueous solution in order to determine the T1 relaxation time behaviour. We observed that by increasing sodium sulfate concentration, the longitudinal spin relaxation time decreases, being this effect more noticeable as the NV centers are closer to the diamond surface and, with respect to the 1/T1 parameter, it gives signs to exhibit a quadratic response with concentration. On the other hand, the T1 values are distributed along the implantation spot diameter, reaching minimum values around the spot center and maximum values at the edges, which is evidence that NV centers with different orientations coexist in the same implantation spot. These results lay the foundation for a possible second stage in our chemical sensor development in which, after certain set-up modifications, new pulse-sequence protocols could be tried.