IBM Research scientists, in collaboration with the Center for Probing the Nanoscale at Stanford University, have developed an MRI with a volume resolution 100 million times finer than conventional MRI, according to research published Jan. 13 in the Proceedings of the National Academy of Sciences.
The authors said that their findings signal a “significant step forward in tools for molecular biology and nanotechnology” by offering the ability to study complex 3D structures at the nanoscale.
By extending MRI to more fine resolution, the scientists have created a microscope that, with further development, may ultimately be powerful enough to unravel the structure and interactions of proteins, paving the way for personalized healthcare and targeted medicine. The achievement stands to impact the study of materials—from proteins to integrated circuits—for which a detailed understanding of atomic structure is essential.
“This technology stands to revolutionize the way we look at viruses, bacteria, proteins and other biological elements,” said IBM Fellow Mark Dean, vice president of strategy and operations for IBM Research.
The accomplishment was enabled by a technique, called MR force microscopy (MRFM), which relies on detecting ultrasmall magnetic forces. In addition to its high resolution, the researchers said that imaging technique has the further advantages that it is chemically specific, can “see” below surfaces and, unlike electron microscopy, is non-destructive to sensitive biological materials.
Now, the team said it has boosted the sensitivity of MRFM and combined it with an advanced 3D image reconstruction technique, which allowed them to demonstrate MRI on nanometer-scale biological objects. The technique was applied to a sample of tobacco mosaic virus and achieved resolution down to four nanometers.
“MRI is well known as a powerful tool for medical imaging, but its capability for microscopy has always been very limited,” said Dan Rugar, manager of nanoscale studies at IBM Research. “Our hope is that nano MRI will eventually allow us to directly image the internal structure of individual protein molecules and molecular complexes.”
The new device does not work like a conventional MRI scanner, which uses gradient and imaging coils. Instead, the researchers said they used MRFM to detect tiny magnetic forces as the sample sits on a microscopic cantilever—a tiny sliver of silicon shaped like a diving board. Laser interferometry tracks the motion of the cantilever, which vibrates slightly as magnetic spins in the hydrogen atoms of the sample interact with a nearby nanoscopic magnetic tip. The tip is scanned in three dimensions and the cantilever vibrations are analyzed to create a 3D image.