Rajat Ghosh
Postdoctoral Scholar
Hyperpolarized MRI is able to image chemical processes in-vivo in real time. This remarkable feat is achieved by utilizing the techniques of dynamic nuclear polarization (DNP), and spin exchange optical pumping (SEOP) to increase the nuclear spin polarization by a factor of 106 over the Boltzmann polarization afforded in clinical and spectroscopic magnets. This significant increase in signal makes it possible to monitor many chemical reactions in-vivo in real time for early detection and progression of several diseases. One example of particular significance is the aberrant elevated conversion of Pyruvate to Lactate in cancer tissue.
However Hyperpolarized MRI is not routinely used in a clinical setting due to several drawbacks. The major “flaw” in the technology is that the nuclear spin signal enhancement is relatively short lived and the polarization enhancement typically decays to the Boltzmann polarization level due to longitudinal relaxation. This limits the time scale of the chemical processes investigated to reactions, and uptake which occur in a short time (10-30s) after injection. This is not sufficient to monitor many chemical processes, especially when the circulation time of the agent to reach the target organ on interest is appreciably long – as is the case in large animal models, and humans. Furthermore the limited polarization lifetime also reduces the image resolution. This is particularly important if the resultant chemical product is not significantly converted during the polarization lifetime.
My work attempts to overcome these hurdles by transferring the nuclear spin polarization to novel quantum states which are either immune, or relatively insensitive to the many longitudinal relaxation mechanisms. Specifically I extend the polarization lifetime by transferring the spin to Singlet-like states which are immune to relaxation from the typically dominant intra-molecular dipolar interaction. The work concerns investigating the interactions of molecules to both study the processes which affect the relaxation of the singlet state due to different relaxation mechanisms and to develop biologically compatible hyperpolarized singlet state biosensors and tracers.
Projects:
- Relaxation of Singlet State Nitrous Oxide
- Hyperpolarized Singlet State Nitrous Oxide
- Singlet State generation of 13C compounds