Non-toxic contrast agent to enhance MRI scanning sensitivity

Early detection of diseases is a very powerful way of saving lives. For example if we catch cancer in the early stages, patients face a much better possibility for treatment and higher survival rate. In this regard, Magnetic Resonance Imaging (MRI) is an important technique for diagnostics.

MRI is a non-invasive method, based on the physical principles of Nuclear Magnetic Resonance (NMR), which exploits the signal coming from the nuclear magnetism of water protons in the body’s soft tissues. It provides insights to the body’s health state without exposing the patient to potentially dangerous ionizing radiations, as for other diagnostic techniques (e.g. CT, X-ray, PET).

Today MRI is routinely used in the healthcare sector for diagnostics purposes and treatment monitoring. Still there is an apparent need for higher reader sensitivity and enhanced contrast on images to ease diagnosis and reduce the number of false positives or false negatives. Furthermore, the use of machine learning for medical imaging classification and interpretation is gaining growing importance. Databases of labeled high quality/contrast images are needed to train the recognition algorithms and develop this new area.

Often gadolinium-based contrast agents are administered to the patients to enhance image quality. However, serious concerns are ascribed to the safety of such contrast agents for specific patient groups e.g. patients with advanced kidney diseases.

Hyperpolarized water as a non-toxic alternative

Now researchers from the HYPERMAG center at DTU Health Tech have come up with a safer alternative.

Postdocs Andrea Capozzi and Arthur Pinon say, “A work around could be to generate ex-situ water gifted with high contrast and inject it into the body prior to examination.”

The HYPERMAG center, where the two researchers conduct their scientific activity, is specialized in dissolution Dynamic Nuclear Polarization (dDNP), a technique that makes it possible to increase NMR sensitivity in the liquid state by generating injectable solutions that are ‘hyperpolarized’. In other words, the NMR signal is increased by 10,000-fold compared to normal.

Hyperpolarization of water is far from trivial. Mainly due to the paramagnetism of stable radicals used in the dDNP process to create the hyperpolarization. These stable radicals, once in the liquid state, cause severe “water contrast” loss, nullifying the efforts made to create the initial hyperpolarization.

A solution to this challenge is to develop methods where non-persistent radicals are used. The research team has recently been working with creating UV-induced thermally unstable radicals.

The two postdocs explain, “We irradiate a solution of water and pyruvic acid with UV-light to create non-persistent radicals. The latter suddenly recombine in biocompatible diamagnetic species right after dissolution of the hyperpolarized sample. With these labile radicals, we were able to hyperpolarize water molecules up to 70% and keep the “high contrast” intact because we got rid of the unwanted paramagnetism in the injectable solution. With our new approach we improved by 14 times the state-of-the-art. So now we have the tool, then the next step will be pre-clinical implementation.” 

Read the article in Chemistry Communication here.