Nanoscale MRI: Innovation in Medical Imaging

by Prasad Kanuparthi

How does a physician, attempting to diagnose a patient with a sensitive condition, peer into the patient’s inner physiological framework without damaging his already precarious state? Since the latter half of the 20th century, imaging techniques have offered non-surgical methods of examining various portions of the body. Of these scans, magnetic resonance imaging (MRI) is very useful when analyzing specific portions of a patient’s body. This technique provides information on the presence of any abnormalities or injuries that lay within the patient’s meshwork of tissue and bone. But how can we improve MRI further?

As the complexity and variability of ailments that people obtain has increased, so has the need to diagnose disease earlier. This has demanded an equal, if not greater, response from the biomedical community, which has in recent years, driven the production of many medical tools to better the condition of society. Of these tools, nanoscale MRI is a landmark advance that could prove to be a foundation for future medical imaging technology.

Through a cooperative research initiative, researchers at both the City College of New York in New York City and the University of Stuttgart in Stuttgart, Germany, designed this new process. As Dr. Carlos Meriles – head of this initiative – stated in an interview from 2013, “It’s bringing MRI to a level comparable to an atomic force microscope … standard MRI typically gets a resolution of 100 microns; nanoscale MRI would have a resolution 1,000 to 10,000 times better.”

This improvement, which increases the resolution from the width of a human hair to the diameter of red blood cells, could one day allow physicians to measure how the very molecules composing a tissue are behaving. By understanding whether abnormal proteins are being produced, if DNA contains mutations, or if cancerous cells are dividing rapidly, physicians would be able to visualize the molecular basis of human pathology. This could potentially allow them to diagnose the patient’s ailment on the actual biological basis and not just on symptoms of the ailment.

The nanoscale MRI operates on generally the same principles as conventional MRI, but applies a different model to image the target substance. Unlike conventional MRI, which uses large magnets, a large chamber, several coils and radio waves, nanoscale MRI uses a small diamond tip, called a cantilever, as an extremely sensitive scanner to pick up the changes in the relative energies of the molecules around the diamond tip. In essence, the nanoscale MRI uses principles from atomic force microscopy, a subset of electron microscopy, combined with that of the conventional MRI to obtain an innovative means of improving magnification, sensitivity and resolution. A scanner detects alterations in the way certain atoms spin and oscillate, a tendency known as resonance. These measured resonances are received by the scanner and transformed into a visible, highly resolved image.

Diamond is composed entirely of carbon atoms in its purest form. However, on the small tip used in the nanoscale MRI, sometimes a carbon atom “falls off” its place in the diamond structure and a nitrogen atom lodges itself in a spot adjacent to where the carbon atom fell off. This forms what is known as a nitrogen vacancy (NV). These NV’s act as extremely effective sensors on the atomic scale, detecting the resonances of the atoms that surround where the diamond tip with the NV’s is placed. By bombarding the atoms surrounding the diamond tip with light, a source of electromagnetic energy, the technique forces surrounding atoms to absorb the energy and spin in a new direction.

It turns out that these NV’s also have a spin and are affected by the changing states of the spins of the adjacent atoms on an unimaginably small scale. A scanner picks up how these NV’s are affected by the surrounding atoms’ fluctuating spin states and produces an image through mathematical modeling. This image can be continually generated over the surface that the diamond tip travels over.

If this tip travels over tissue, for example, or is adapted in the future such that it scans underneath skin at the tissue below, then a real-time image of the molecular mechanisms occurring on the cellular level in the patient may be obtained and used to create an accurate diagnosis. For example, a significant cause of cancerous growth in the body stems from mutations of various proteins, termed tumor suppressor proteins, which normally work to regulate the division and proliferation of cells. Perhaps, with development, the nanoscale MRI may one day be able to non-invasively screen a portion of a patient’s body to identify whether or not he possesses any uncontrolled cellular division or a mutation of a tumor suppressor protein. This analysis would contribute to early detection of possible oncogenic activity, which would translate to saving countless lives.

The limits on application of this novel medical technology are yet to be seen. In the same way this technology stemmed from conventional MRI and high-resolution microscopy, hopefully more novel technologies will emerge from this innovation, leading to newer and more effective biomedical applications.