Prolonging and Boosting NMR Signals with Long-lived States and Catalytic Polarization Transfer
Nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI) are powerful and versatile tools that are being broadly and intensively used. Their application ranges from molecular structure determination to medical imaging diagnosis. Though NMR and MRI have great advantages such as high chemical environment sensitivity and non-invasive imaging ability with deep penetration, current magnetic resonance (MR) methodologies have fundamental limitations: they mainly use proton as signal source and provide primarily structural information. There are great challenges using MR to obtain metabolic information: for the life supporting elements carbon and nitrogen, their MR non-silent isotopes are in extremely low concentration and the signal they yield is extremely weak under thermal conditions. In addition, their short-lived signal gives us very limited time window to perform complicated experiments. Thus, it is of great significance to obtain long-lived and enhanced NMR and MRI signals for 13C and 15N. Doing so would not only augment information for in vitro chemical analysis, but also make it possible for metabolism monitoring, disease early diagnosis and treatment assessment.
This dissertation will first show how we can make the signals long-lived using molecules with specific structures and sophisticated NMR pulses. Then, based on the concept of the long-lived state, it will demonstrate how we can obtain both enhanced and long-lived signals for 13C and 15N spin-pairs with the development of a novel hyperpolarization technique. This technique is robust, cost-efficient and straight-forward to operate comparing to other existing hyperpolarization methods. Though extra endeavor is needed to develop this hyperpolarization technique towards in vivo applications, numerical simulations and experimental results readily show that it can be improved and applied for in vitro chemistry analysis.
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