Scientists at the University of Nottingham have taken a major step towards providing a much clearer picture of lung disease thanks to new scanning technology developed at its Sir Peter Mansfield Imaging Center. The new process makes the spaces inside lungs show up on a magnetic resonance imaging (MRI) scan using specially treated krypton gas as an inhalable contrast agent. Researchers hope the new process will eventually allow doctors to virtually see inside the lungs of patients.
Traditional magnetic resonance imaging uses hydrogen protons in the body as molecular targets to give a picture of tissue, but this does not give a detailed picture of the lungs because they are full of air. Recent technological developments have led to a novel imaging methodology called Inhaled Hyper-polarized Gas MRI, a process that uses lasers to ‘hyper-polarize’ a noble (inert) gas that aligns (polarizes) the nuclei of the gas so it shows up on an MRI scan.
The work will make 3D imaging using “atomic spies” like helium, xenon or krypton possible in a single breath hold by the patient. Nottingham has pioneered hyper-polarized krypton MRI and is currently advancing this technology towards the clinical approval processes.
Hyper-polarized MRI researchers have been trying to overcome a problem with these noble gases retaining their hyper-polarized state for long enough for the gas to be inhaled, held in the lungs and scanned. Now in a paper published in the Proceedings of the National Academy of Sciences, the Nottingham team has developed a new technique to generate hyper-polarized krypton gas at high purity, a step that will significantly facilitate the use of this new contrast agent for pulmonary MRI.
“It is particularly demanding to retain the hyper-polarized state of krypton during preparation of this contrast agent,” says Thomas Meersmann, chair in translational imaging at the Sir Peter Mansfield Imaging Center. “We have solved a problem by using a process that is usually associated with clean energy related sciences. It’s called catalytic hydrogen combustion. To hyper-polarize the krypton-83 gas we diluted it in molecular hydrogen gas for the laser pumping process. After successful laser treatment the hydrogen gas is mixed with molecular oxygen and literally exploded away in a safe and controlled fashion through a catalyzed combustion reaction.”
The hyper-polarized state of krypton-83 survives this combustion event. Water vapor, the sole product of the clean hydrogen reaction, is removed through condensation, leaving behind the purified laser-polarized krypton-83 gas diluted only by small remaining quantities of harmless water vapor. This development, Meersmann says, significantly improves the potential usefulness of laser-pumped krypton-83 as MRI contrast agent for clinical applications.
This new technique can also be used to hyper-polarize another useful noble gas, xenon-129, and may lead to a cheaper and easier production of this contrast agent. As part of a recent Medical Research Council funding award, hyper-polarized krypton-83 is currently being developed for whole body MRI at high magnetic field strength in the Sir Peter Mansfield Imaging Center’s large 7 Tesla scanner. Studies will be carried out first on healthy volunteers before progressing to patient trials at a later phase.