Microtags Make MRI ’See’ in Color

Scientists from the National Institute of Standards and Technology (NIST) and the National Institutes of Health (NIH) have developed customized microscopic magnets called microtags that might one day be injected into the body and make magnetic resonance imaging (MRI) colorful. The new magnets can also function as “smart tags”, identifying specific cells and tissues and will likely enhance sensitivity and the amount of information which could be obtained from MRI images, improving diagnostic abilities.




Microscopic magnets designed and tested in a joint NIST/NIH project might one day be injected into the body to add color and “smart tag” capabilities to magnetic resonance imaging used in medical diagnosis and research (Credit: G. Zabow, NIST/NIH).
Microscopic magnets designed
and tested in a joint NIST/NIH project
might one day be injected into the body to
add color and “smart tag” capabilities
to magnetic resonance imaging used
in medical diagnosis and
research (Credit: G. Zabow, NIST/NIH).

Gary Zabow designed and fabricated the microtags at NIST and together with colleagues at the National Institute of Neurological Disorders and Stroke, part of NIH, tested them on MRI machines. The tags are similar in concept to the tags used for identifying and tracking objects in nationwide box shipments and products in supermarkets.

Currently, to enhance an MRI image and differentiate between tissues chemical solutions are used. The micro magnets developed by the NIST/NIH scientists differ in their shapes and therefore produce different RF (radio frequency) waves. The varying RF signals could be interpreted as different colors. Ideally, different RF signals would originate from different tissues. This would make differentiating between cancerous and normal cells possible to in an MRI image.

The micromagnets are constructed from two round magnetic discs which have a small open gap between them. The customized field is created per tag by altering the materials they are made from or changing their geometry by playing with the discs’ properties. In the sample, water creates a flow through the discs and the protons act like rotating bar magnets within the waters’ hydrogen atoms, thus creating predictable RF signals. The stronger the magnetic field, the faster the rotation that’s translated to a signal by the MRI.

The signals the microtags create are much stronger than those of moving water molecules due to their shape and material composition. They increase local MRI sensitivity dramatically, which in a future clinical setting could lead to practical benefits such as faster imaging and images that contain richer information. Changes in magnet geometry result in large shifts in the frequency signals, thus making it easier for the MRI to pick up the changes. This will potentially work better than the conventional use of MRI contrasting agents, which are chemicals inserted into the body. Also, the microtags have the potential of being detected on an individual basis. 

This image shows light scattering from grids of magnets on a wafer where they were made using conventional microfabrication techniques (Credit: G. Zabow, NIST/NIH) 
This image shows light scattering
from grids of magnets on a
wafer where they were made using
conventional microfabrication
techniques (Credit: G. Zabow, NIST/NIH)

The microtags will probably be manufactured by conventional microfabrication methods, but perhaps with time it will be possible to create them using more sophisticated techniques such as advanced lithography. This could enable making the tags on the nanometer scale while still retaining their magnetic properties.

The tags are still not ready for use on patients during an MRI scan and need to undergo further testing. So far, the metals used for creating them have been toxic and researchers need to find a magnetic material that can be inserted into the body safely. Only very low concentrations of magnetic material are needed, therefore, once perfected microtags might become a safe option for high resolution MRI mapping. 

TFOT has recently covered other developments in the MRI imaging field. One such story also comes from the National Institute of Standards and Technology in Boulder, Colorado, telling of tiny magnetic sensors that may help shrink the MRI machine. Another related TFOT article is about research conducted at the National High Magnetic Field Laboratory’s Applied Superconductivity Center. Scientists there have discovered surprising magnetic properties in new superconductors, which could help create improved MRI devices.

The press release from NIST can be found at the NIST website.