Optical Hyperpolarization of Noble Gases for Medical Imaging
Magnetic resonance imaging (MRI) of human or animal lungs became possible with the application of hyperpolarized noble gases, such as 3He or 129Xe. This method allows obtaining information on lung morphology and functionality. Introduction of hyperpolarized noble gases provided as well a new tool for non-medical applications such as neutron filters or nuclear magnetic resonance (NMR) spectroscopy studies in porous materials. The high polarization of noble gases is possible using so-called optical pumping methods. In this chapter the two most common polarization techniques of noble gases (3He and 129Xe), spin exchange optical pumping (SEOP) and metastability exchange optical pumping (MEOP) are presented. Variations of these methods delivering higher 3He and 129Xe polarization including hybrid SEOP or MEOP in standard conditions and in elevated pressure and high magnetic fields are also reported. A short description of the equipment used for gas polarization is also provided.