Conventional MRI uses the small thermal-equilibrium polarization of protons in a strong magnetic field as the signal source. This technique relies on the abundance of water in biological environments. However, imaging organs with low water concentration presents a unique challenge to MRI technology. Very recently, with a new technique, called hyperpolarization, developed by the Physics Department at Princeton, it is possible to produce non-equilibrium magnetization by optical pumping. Optical pumping is an effective method to produce polarized 3He and other noble gases. In this scheme, laser light provides angular momentum that is first transferred into the electron of an atom and subsequently into the nucleus of noble gas. This process produces non-equilibrium magnetization in which the NMR signal intensity is enhanced by a factor of about 105. The overall goal of our project is to develop novel magnetic resonance imaging (MRI) schemes which utilize hyperpolarized noble gases (3He and 129Xe). This allows physicians to image organs in situations where conventional nuclear magnetic resonance signals suffer from low proton density, i.e. low signal . We have setup an optical system that is equipped with a diode array laser, necessary optics, and other accessories to produce high power circularity polarized light. Our set up has been successfully used to polarize 3He through spin-exchange process. We plan to use this setup to image human lung and use in other clinical applications.
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