Novel NMR / MRI Contrast Method for Imaging based on Antiphase Signals
In vivo magnetic resonance spectroscopy and magnetic resonance imaging (MRI) play a very important role in medicine. The sensitivity is one of the challenges in the MRI technique, as background signal typically masks the signal obtained from detection of small number of molecules of interest. The low sensitivity is usually addressed using the technique of hyperpolarization, which increases nuclear magnetic resonance (NMR) signals up to five orders of magnitude. This strategy is, however, limited for 1H, the most widely used NMR and MRI nucleus, as the vast number of protons in the body screen the small amount of the hyperpolarized ones.
The technology presents a simple approach using the difference in time evolution of the hyperpolarized 1H signal compared to the background signal, and chooses an optimal delay for detection of signal from small number of molecules of interest.
- The well-known NMR technique of Parahydrogen Induced Polarization (PHIP) is utilized that results in enhancement of absorption and emission signal by a factor of 105.
- The characteristic absorption and emission signal (i.e. the antiphase signal) largely cancel each other and are usually not considered as primary source of signals in MRI. Instead, their polarization is transferred to hetero nuclei, which result in loss of signals. The method used here is based on self-refocusing of the PHIP protons that leads to excellent contrast to thermally polarized protons even for low concentration of hyperpolarized substance.
- The contrast can be created in clinical MRI scanners. All MRI experiments were performed on standard 1.5 T human imaging system.
- The proof-of-concept is presented using the model system hexene.
- Subsequent to hyperpolarization and after 10 ms, the signal is dominated by the very intense hyperpolarized signal of two PHIP protons, although there is 700-fold excess in thermally polarized protons.
- The new method for producing contrast images can be used for all molecules that can be polarized using PHIP.
- Biologically relevant molecules, such as succinate (citric acid cycle) and barbiturate (pharmaceuticals) can be used as contrast agent using the newly developed method.
PCT application WO2011076228 filed on 21.12.2009.