hyperpolarizáció

Hyperpolarizáció is a phenomenon in physics and chemistry where the nuclear spins of certain atoms are aligned to a much greater degree than they would be in thermal equilibrium. This enhanced alignment leads to a significantly amplified NMR (Nuclear Magnetic Resonance) or MRI (Magnetic Resonance Imaging) signal.

The process typically involves preparing a sample in a non-equilibrium state where the population of spins in different energy levels is skewed. This can be achieved through various techniques, including optical pumping, spin exchange, or brute-force polarization. Optical pumping, for instance, uses lasers to transfer angular momentum to the nuclei, creating a population imbalance. Spin exchange involves transferring polarization from a highly polarized electron reservoir to the target nuclei.

The resulting hyperpolarized state is transient, meaning the spins gradually relax back to their thermal equilibrium distribution. However, during this period, the amplified signal allows for much faster data acquisition or the detection of signals from much lower concentrations of the substance.

Hyperpolarization has found significant applications in medical imaging, particularly in MRI. It enables real-time imaging of metabolic processes in vivo, offering insights into diseases like cancer and cardiovascular conditions. It is also used in fundamental scientific research to study molecular dynamics and structure with enhanced sensitivity.