Rare Earth Elements in Medicine

I had the good fortune of being invited by the Canadian Institute of Mining and Metallurgy to organize and moderate a Rare earth panel at its annual Conference, this year convened in Edmonton May 6th-9th). The theme of the conference was ‘From Prospect to Product’. The CIM is also committed to engaging student participation in its programs.

I had the good fortune to be introduced to Josh Rosen of the University of Waterloo’s Department of Chemical Engineering some months earlier. So I took the liberty of inviting Josh to sit on the panel, asking that he enlighten the audience on where Rare Earths/Rare Metals are used in medicine. As an added bonus, I invited Josh to summarize two examples for RareMetalApps, and he share’s his thoughts below…

“Rare earth elements (REEs) have many applications in modern industries ranging from electronics and energy to medicine. Their unique properties such as radiation emission or magnetism allow REEs to be used in many different therapeutic and diagnostic applications in modern medicine. Currently there are a few major applications of REEs in medicine but many more of them are on the horizon. In this blog post, I will examine a few of the current major applications of REEs and offer some thoughts on how emerging advancements such as nanotechnology might be used to enhance them in the future.

Magnetic Resonance Imaging (MRI) Contrast Agents
MRI is a medical imaging technique that uses strong magnetic fields to image soft tissues in the body without using any form of radiation. However, sometimes physicians wish to obtain greater contrast on an image in order to more accurately distinguish an abnormality such as a tumour, or perhaps to map out the blood vessels in a particular area of the body (magnetic resonance angiography). In these cases, a material called a contrast agent is often administered to the patient.
MRI of a brain without (left) and with (right) a contrast agent showing the effects of a stroke.

Contrast agents for MRI are typically magnetic materials that cause a change in the magnetic behavior of the tissues in which they accumulate. Since it is the “magnetic behavior” of the tissue, which produces contrast on an MRI image, a change in these magnetic properties will produce a corresponding change in contrast. Many of the frequently used contrast agents for MRI are based on the REE gadolinium (Gd), which is paramagnetic. Currently, there are many different types of Gd based contrast agents approved for use by the FDA. They all utilize different chemical entities to stabilize (or chelate) the Gd ions and thus have different patterns of distribution throughout the body, making them suitable for different applications.

One trend that may emerge in future MRI contrast agents is that we will be able to exert greater control over where they distribute in the body and how long they reside in the body. For example, using various techniques from the field of nanotechnology, researchers are working to develop contrast agents that are capable of specifically recognizing tumours, making them even easier to spot on an MRI image, which allows for earlier diagnosis and treatment. Furthermore by controlling how rapidly the contrast agent is cleared from the blood, researchers can develop better materials for examining blood vessels, allowing physicians to acquire even higher resolution images.

Radiotherapy Treatment of Liver Cancer
In addition to diagnostic applications REEs can also be used in many types of medical treatments. One currently approved therapeutic application of REEs is the use of Yttrium-90 (Y-90) microspheres for the treatment of liver cancers. Y-90 is an emitter of beta radiation, which is capable of damaging and killing living cells. In its current application, Y-90 is encapsulated in microspheres (particles with size of 20-30 mm, one mm is a millionth of a meter) that are then directly injected into the blood vessels feeding a tumour using a catheter. Their larger size causes the microspheres to become lodged in these blood vessels where they can deliver a strong dose of radiation to the cancer and work to cut off its blood supply. This treatment is referred to as radioembolization (radio = radiation, embolization = cutting off the blood supply). Since beta radiation only travels a few millimeters inside the body, radiation damage to the surrounding healthy liver tissue is generally minimized.

Currently, Y-90 radiotherapy is generally restricted to liver tumours and it requires a significant amount of pre-planning by the physician. It is very important that the physician use multiple medical imaging techniques in order to map out the structures of the blood vessels to ensure that the radioactive spheres will be deposited into the liver tumour, and not into healthy liver tissues or into areas where they can bypass the liver and travel to other parts of the body (e.g. the lungs).
In the future, Y-90 may be able to be used to treat other types of cancer. For example, using similar techniques to those described above for Gd, Y-90 can be encapsulated into smaller nanoparticles and directed to other sites in the body through various targeting methods. This can help physicians and researchers to gain greater control over the tissue distribution and circulation properties of these materials. Furthermore, Y-90 can be combined inside of a delivery system with other treatments such as chemotherapeutics in order to deliver multiple therapeutic agents to a tumour simultaneously.

These are just two of the ways in which REEs are being used in medicine today. There are many more applications such as MRI magnets, medical lasers, surgical implants, and fluorescent materials for sensors and diagnostics. As advances in areas such as nanotechnology continue to be made, new areas of application for REEs in medicine are sure to open up which will allow their unique properties to be applied to the diagnosis and treatment of even more medical conditions.”

Need I say anymore about the talent that the next generation brings to addressing today’s challenges? Not really – Josh and many of his classmates have surely demonstrated that they can speak for themselves.