Magnetic resonance imaging (MRI) provides excellent soft tissue contrast and enables structural, functional, and metabolic imaging of the human body. One primary clinical application of MRI is the neuroimaging of tumors, which demands both multi-parametric qualitative and quantitative information from MR scans. Although the role of the quantitative MRI (qMRI) is well accepted, it suffers from long acquisition times leading to patient discomfort, especially in geriatric and pediatric patients. Quantitative imaging is also critical to estimating temperature during MR scans of patients with implants and leads. The radiofrequency stimulus pulses of an MRI exam can couple to conductive implants, resulting in eddy current propagation and consequential heating. The heating can lead to third-degree burn lesions along the surfaces of titanium joints, deep brain stimulation (DBS), and pacemaker leads. Such challenges raise safety concerns in MRI, requiring fast and accurate temperature estimations to ensure patients’ safety. This thesis aims to tackle the abovementioned challenges in MRI, specifically focusing on developing novel quantitative imaging approaches using magnetic resonance fingerprinting (MRF) methods and applications. MRF is a framework that allows measuring multiple tissue properties in a single acquisition. In the first chapter, we extend the current implementation of MRF and introduce tailored MRF (TMRF), an imaging method offering qualitative and quantitative information simultaneously, with promising results in differentiating healthy and pathological tissues. This method increases scanner efficiency and decreases acquisition time for neuroimaging while simultaneously providing qualitative and quantitative imaging measures. We demonstrate these advances in in vitro phantoms healthy volunteers- and pediatric patient- populations. In the second chapter, we address the issue of MRI safety for patients with conductive implants like deep brain stimulation (DBS) leads by using MRF-based thermometry (MRFT) to accurately predict and monitor temperature near these implants during MRI scans, enhancing safety and efficacy for image-guided procedures and imaging patients with such implants. Successful approaches will be incorporated into an imaging protocol to increase safety and effectiveness for image-guided lead placement and imaging patients with implanted leads. To validate MRFT in vivo in patients, we conducted a patient study using MRFT to evaluate the accuracy of MRFT in vivo near DBS lead. In the third section, we implement an open-source MRF package (OMEGA) for a multi-site, multi-field strength MRF repeatability study, demonstrating its accuracy and repeatability of MRF across various conditions.

A eletrocirurgia é uma técnica cirúrgica que utiliza o bisturi elétrico para a realização do corte, dessecação e coagulação do tecido orgânico, diminuindo dessa forma os riscos de hemorragia. O bisturi elétrico usa o processo da faiscância para a realização do trabalho. Esse processo provoca, entre outras coisas, o aquecimento da água intracelular e, consequentemente, o rompimento da célula do tecido. Embora se saiba a quantidade de energia entregue pelo bisturi elétrico, pouco se sabe sobre as parcelas de energia envolvidas nos vários fenômenos do processo eletrocirúrgico, principalmente no corte, onde as células sofrem ablação por vaporização. Com base neste problema, foi desenvolvida esta pesquisa, que teve o objetivo de determinar a energia necessária para o corte eletrocirúrgico, através dos parâmetros elétricos envolvidos e da energia utilizada para a vaporização da água do tecido orgânico. O método desenvolvido foi testado em três experimentos, com várias séries de cortes específicos em cada. Demonstrou-se que da energia total que é entregue pelo bisturi, menos de 10% é utilizada para o corte, ou especificamente, para a vaporização da água do tecido. O restante da energia acaba sendo utilizada em outros processos que começarão a ser analisados em outros trabalhos. / Electrosurgery is a surgical technique that uses an electrosurgical device for cutting, drying (desiccation), and coagulation of organic tissue, thereby reducing the risk of bleeding. Electrosurgical device uses sparking phenomena for this purpose. This process causes heating of intracellular water and, consequently, the rupture of the cell in the organic tissue. Although the amount of energy delivered by the electrosurgical device is easy to know, little is known about the exactly amount of energy involved in the various phenomena of electrosurgical procedure, especially in cutting, where cells suffer ablation by vaporization Based on this was developed this research, which objective is to determine the energy required for the electrosurgical cutting through the electrical parameters involved and the energy used for the vaporization of water of organic tissue. The method developed was corted in three experiments, with a series of specific tests in each. It has been show that only about 10% of total energy is used for cutting, or specifically, for the vaporization of water of organic tissue. The rest of the energy is used in other processes that need more investigation to be understood.

A eletrocirurgia é uma técnica cirúrgica que utiliza o bisturi elétrico para a realização do corte, dessecação e coagulação do tecido orgânico, diminuindo dessa forma os riscos de hemorragia. O bisturi elétrico usa o processo da faiscância para a realização do trabalho. Esse processo provoca, entre outras coisas, o aquecimento da água intracelular e, consequentemente, o rompimento da célula do tecido. Embora se saiba a quantidade de energia entregue pelo bisturi elétrico, pouco se sabe sobre as parcelas de energia envolvidas nos vários fenômenos do processo eletrocirúrgico, principalmente no corte, onde as células sofrem ablação por vaporização. Com base neste problema, foi desenvolvida esta pesquisa, que teve o objetivo de determinar a energia necessária para o corte eletrocirúrgico, através dos parâmetros elétricos envolvidos e da energia utilizada para a vaporização da água do tecido orgânico. O método desenvolvido foi testado em três experimentos, com várias séries de cortes específicos em cada. Demonstrou-se que da energia total que é entregue pelo bisturi, menos de 10% é utilizada para o corte, ou especificamente, para a vaporização da água do tecido. O restante da energia acaba sendo utilizada em outros processos que começarão a ser analisados em outros trabalhos. / Electrosurgery is a surgical technique that uses an electrosurgical device for cutting, drying (desiccation), and coagulation of organic tissue, thereby reducing the risk of bleeding. Electrosurgical device uses sparking phenomena for this purpose. This process causes heating of intracellular water and, consequently, the rupture of the cell in the organic tissue. Although the amount of energy delivered by the electrosurgical device is easy to know, little is known about the exactly amount of energy involved in the various phenomena of electrosurgical procedure, especially in cutting, where cells suffer ablation by vaporization Based on this was developed this research, which objective is to determine the energy required for the electrosurgical cutting through the electrical parameters involved and the energy used for the vaporization of water of organic tissue. The method developed was corted in three experiments, with a series of specific tests in each. It has been show that only about 10% of total energy is used for cutting, or specifically, for the vaporization of water of organic tissue. The rest of the energy is used in other processes that need more investigation to be understood.