Our laboratory is interested in developing new methodologies for magnetic resonance imaging and spectroscopy to increase sensitivity and contrast specificity. A strong emphasis is placed on understanding the physics of MRI hardware and contrast generation, as well its biomedical imaging applications.
Nuclear Spin Hyperpolarization Nuclear Spin hyperpolarization provides a mean to amplify the signals from nuclear spins that would otherwise go unnoticed. There are several ways to increase nuclear spin polarization. In the case of nobel gases this is most commonly achieved by spin-exchange optical pumping (SEOP), a process whereby circularly polarized (laser) light is used to optically pump and spin-polarize valence electrons of an alkali-metal vapor. Through the hyperfine interaction, spin polarization is then transferred from the electrons of the alkali metal to the nuclei of the nobel gas. Applications of spin-polarized Nobel gases range from physics, chemistry, material science, and biomedical imaging. Our lab is interested in the physics of SEOP as well as on its biomedical imaging applications. For additional information on spin exchange optical pumping techniques and its application you can read this review article.
Low and ultralow field MRI
MRI at ultralow field is a rapidly developing area of research that has the potential to revolutionize medical imaging. Unlike traditional MRI, which operates at high magnetic fields of several tesla, ultralow field MRI operates at magnetic fields of only a few millitesla. This has several advantages, including lower costs and reduced safety concerns. However, one of the challenges of ultralow field MRI is that it typically requires longer scan times and lower signal-to-noise ratios compared to high field MRI. This is because the signal from the spins is weaker at lower fields, and the contrast between different tissues is lower. One approach to addressing this challenge is to combine ultralow field MRI with nuclear spin hyperpolarization techniques.
In a recent cover article in ChemPhysChem, we demonstrated the direct detection of polarization transfer from highly polarized 129Xe gas spins to 1H spins through the nuclear Overhauser effect. By introducing hyperpolarized 129Xe gas into a solution, we were able to achieve a remarkable enhancement of 1H polarization levels, reaching up to more than 150-fold increase. While the reported enhancements may be slightly lower than those achieved under extreme Xe gas pressures at high magnetic field strengths, the real value lies in the repeatability and on-demand nature of this enhanced spectroscopy protocol.
Additionally, at magnetic field strengths where thermal nuclear spin polarization nearly blends with background noise levels, and various nuclei can be simultaneously detected in a single spectrum, one can directly witness the intricate details of the polarization transfer process.