Applications of clever pulse sequences to detect the xenon-129 biosensor with enhanced sensitivity and for a fast imaging technique

Hyperpolarized xenon associated with ligand derivatized cryptophane-A cages has been previously developed as a NMR based biosensor. Different characteristics of the xenon biosensor are explored and optimized. A flow-mode delivery apparatus to enhance the sensitivity of xenon in solution experiments is presented along with pulse sequences designed to work with the bubbling apparatus and chemical properties of the xenon biosensor to achieve maximum sensitivity.;To optimize the detection sensitivity of the xenon biosensor, xenon exchange between the caged and bulk dissolved xenon is developed as an effective signal amplifier. This approach, somewhat analogous to 'remote detection' described recently, uses the chemical exchange to repeatedly transfer spectroscopic information from caged to bulk xenon, effectively integrating the caged signal. After an optimized integration period, the signal is read out by observation of the bulk magnetization. The spectrum of the caged xenon is reconstructed through use of a variable evolution period before transfer and Fourier analysis of the bulk signal as a function of the evolution time.;HyperCEST utilizes the chemical exchange of xenon associated with the biosensor for imaging contrast. Temperature, saturation power, saturation delay, and concentration affect the achieved sensitivity for this experiment. Experiments exploring the parameter space are presented along with a model describing the system.;The multiple-modulation-multiple-echo (MMME) sequence, previously used for rapid measurement of diffusion, is extended to be a method for single shot imaging. Replacing the gradient switching during the application of RF pulses by a constant frequency-encoding gradient can shorten experiment time for ultrafast imaging. However, having the gradient on during the pulses gives rise to echo shape variations from off-resonance effects, which makes the image reconstruction difficult. In this study, we propose a simple method to deconvolve the echo shape variation from the true one-dimensional image. This technique in combination with half Fourier imaging can produce a single-shot image of sub-millimeter resolution in 5 milliseconds.