Hyperpolarized MRI
Magnetic Resonance Imaging (MRI) has been used for many years to acquire images of the soft tissue inside the body. Typically, MRI measures hydrogen (1H) nuclei, but it is possible to observe other nuclei, such as carbon-13 (13C) and nitrogen-15 (15N). These other nuclei are interesting, because they are involved in metabolic processes in the body. It is known that changes in metabolic processes often cause and/or precede diseases, so being able to observe these changes in the body is very important for early diagnosis and understanding diseases. Acquiring spectra or images inside the body using nuclei other than 1H is difficult. The low natural abundance of 13C and 15N and the poor polarisation of these nuclei in a magnetic field results in very little signal. In order to acquire the simplest spectra or images of these nuclei would require many, many hours.
;A new development in MRI, called Dynamic Nuclear Polarisation (DNP), has enabled acquisition of spectra and images from nuclei other than 1H in more reasonable times. The problem of low natural abundance can be overcome by replacing the 12C with 13C in a molecule of interest. The problem of poor polarisation is overcome by the DNP process. This involves placing the 13C-enriched molecule in a magnet and supplying the electrons surrounding the 13C with energy. The electrons transfer this energy to the 13C nuclei resulting in increased polarisation, or hyperpolarisation, of the 13C. When the 13C-enriched, hyperpolarised molecule is injected into the body, a 10,000-fold increase in signal is obtained. With this increase, spectra or images can be acquired in a matter of minutes enabling the ability to monitor metabolic processes in the body.
