Browsing by Subject "MRS"

Now showing 1 - 3 of 3
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    Development and Validation of a Multinuclear Magnetic Resonance Spectroscopy Toolkit for Bioartificial Pancreas Assessment
    (2016-06) Einstein, Samuel
    Type 1 diabetes is a devastating disease with increasing incidence and prevalence. Insulin therapy, while life-saving, does not prevent severe complications that substantially increase both morbidity and mortality. Whole pancreas and pancreatic islet transplantation are treatments for diabetes, but favorable long-term outcomes are inconsistent and the procedures are restricted to a small group of patients due to a variety of limitations. These impediments include the current demand for donor pancreata far exceeding supply, allotransplantation requiring a lifetime of immunosuppression, and premature graft failure. Macroencapsulated tissue-engineered grafts (TEGs) may mitigate or eliminate these limitations by allowing the use of alternative cell sources (such as porcine or stem-cell-derived islets), providing immunoisolation, and encourage graft survival through therapeutic interventions. TEGs possess great potential, but require significant development to fulfill their promise of a safe, effective, and definitive cure for type 1 diabetes. To enable and expedite TEG development, novel techniques to assess oxygen status (pO₂) and viability were developed, validated, and applied. Hypoxia is currently the most significant obstruction preventing widespread utilization of TEGs, rendering measurements of TEG pO₂ critically necessary. Fluorine-19 magnetic resonance spectroscopy (¹⁹F-MRS) was adapted for in vivo pO₂ measurement in TEGs and validated with a well-established technique. It was found that ¹⁹F-MRS can be a robust, accurate, and noninvasive technique to monitor TEG pO₂ for long durations post-implantation. This technique was applied to the murine model and demonstrated that TEGs implanted subcutaneously experience hypoxia unconducive to supporting islet viability and function. Therefore, a method for the delivery of supplemental oxygen (DSO) to increase in vivo pO₂ was developed and its efficacy was evaluated with ¹⁹F-MRS. It was found that DSO can successfully increase the pO₂ of macroencapsulated TEGs and enhance islet survival. While providing crucial information, measuring pO₂ does not necessarily correlate to islet viability, necessitating the development of additional techniques. Islet viability was first assessed by measuring pO₂ with ¹⁹F-MRS and calculating the oxygen consumption rate (OCR) using a mathematical model. Finally, to facilitate in vivo viability assessment and increase measurement accuracy, oxygen-17 MRS was developed to directly measure and noninvasively quantify the OCR of TEGs.
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    MRS fitting challenge data setup by ISMRM MRS study group
    (2021-04-16) Marjanska, Malgorzata; Deelchand, Dinesh K; Kreis, Roland; gosia@umn.edu; Marjanska, Malgorzata
    Fitting of the magnetic resonance spectroscopy (MRS) data plays an important role in the quantification of metabolite concentrations. A number of commercial and home-built packages are available and used by the MRS community to fit spectra. The question arose whether any one of these packages was superior to the others or whether they all perform similarly if appropriately used. Hence, in preparation for a workshop of the ISMRM MRS study group on MR Spectroscopy: from Current Best Practice to Latest Frontiers, which took place in August 2016, it was decided by the organizing committee, that this question should be tackled by a fitting challenge open to everybody, where a set of spectra would be evaluated. For this purpose, synthetic MRS data were generated for 28 datasets. Short-echo time PRESS spectra were simulated using ideal pulses for the common metabolites at mostly near-normal brain concentrations. A macromolecular contribution was also included. Modulations of signal-to-noise ratio (SNR), lineshape type and width, concentrations of γ-aminobutyric acid, glutathione and macromolecules, and inclusion of artifacts and lipid signals to mimic tumor spectra were included as challenges to be coped with.
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    Pak Mun Dam and its Impact on Local Residents of Ubon Ratchathani Province, Thailand: A Quantitative Analysis
    (2020-11) Chaiyamart, Pattaraphongpan
    Many dams have been built along the Mae Khong River, bringing up many issues, including that of sustainable livelihood. Pak Mun Dam is one of the most controversial dams in Thailand, and its issues have continued to today. While many studies on dams have been conducted, this is the first quantitative study, using the Structural Equation Model to understand the eight dimensions of well-being. The survey on which this dissertation is based collected 250 pieces of data for the impacted community and 250 pieces of data for the non-impacted community of the Khong Jiam district in the Ubon Ratchathani province of Thailand. The eight dimensions of well-being are based on concepts and theories about achieving sustainable livelihoods. Within these eight dimensions, there are 24 out of 40 items that have a lower mean for the impacted community, in comparison to the non-impacted community, which is statistically significant. Based on the sustainable livelihood framework model, institutions (in this case, the government) play the role of providing strategies to increase well-being assets directly in terms of overall well-being and through dimensions of well-being. In this model, the government’s interventions are public services, quality of job training, and the satisfaction level for the Pak Mun Dam solution. The empirical results of the first order factors show that there are seven factors that are statistically included as first order factors with twenty items. These twenty items represent the factors of economics, community, environment, politics, working conditions, culture, and family. Second order factors were included in the structural model as independent variables in order to predict the dependent variable of overall well-being. Economic well-being and social well-being are statistically significant factors for predicting overall well-being; they can also be mediators of the model. The results from the structural model show that there is full mediation within this model, which means that the government’s impact on overall well-being can only be explained through increasing economic and social well-being. The satisfaction level of Pak Mun Dam’s government solution would impact overall well-being through the mediation of economic well-. The government’s quality of job training and the provision of government services would impact overall well-being through social well-being. In addition to the benefit of standardized estimates of economic and social well-being, the institutions can use the twenty items to help specify factors and provide better policy to maintain sustainable livelihoods based on their precise information. The marginal rate of substitution (MRS) result also shows the relationship between economic well-being and social well-being: local community residents would give up more of their economic well-being to gain more social well-being. This shows that their social well-being is a very important factor for their livelihoods. The study is significant for six reasons. First, it is the first quantitative study of the well-being of local residents impacted by the dam; it also provides more complete information and deeper understanding about each dimension of well-being. Second, this study is the first study that combines more dimensions of well-being based on SLF into a single study. Third, it has furthered the work of existing studies with SEM to SLF to investigate the impact of the dam. Fourth, it informs policymakers so that they can provide more suitable policies to achieve sustainable livelihoods. Fifth, the study also adds the MRS concept to understand local residents’ decision-making process on well-being, and it can be used to create the well-being index and trade-off analysis for SLF projects. Last, testing the important of institute with specific needs of local residents would be more efficient for SLF project.