Hyperpolarized ³He gas production and MR imaging of the lung

Optical polarization of ³He generates large nuclear spin magnetizations, allowing MR imaging of the gas spaces of human and animal lungs despite the low number density of spins in the gas. The atomic physics of optical pumping and spin exchange is explained; the hardware for polarizing, transporting, and imaging is detailed. Pulse sequences for optimum use of the nonrenewable magnetization require a different imaging strategy than traditional proton MRI. Examples are discussed for static lung images, diffusion images for characterization of the local alveolar structure, and high temporal resolution images.