Researchers from Caltech are utilizing cutting-edge MRI techniques to better understand what happens in tissues at scales as small as a single micrometer—about 500 times smaller than what is currently possible.
The researchers developed a method to correlate magnetic field patterns in tissue—which occur on the micrometer scale—with the larger, millimeter-scale features of MRI images, allowing doctors to interpret MRI pictures and better diagnose various conditions.
“When you look at a splotchy MRI picture, you may want to know what’s happening in a certain dark spot,” Mikhail Shapiro, an assistant professor of chemical engineering, said in a statement. “Right now, it is hard to say what’s going on at scales smaller than about half a millimeter.”
Different tissues in the body react to magnetic fields in different ways, generating images of human anatomy. However, the resolution of the images limits doctors to examining details of organs as small as a half millimeter in size, but not much smaller.
The researchers optically probed magnetic fields in mammalian cells and tissues with submicron resolution and nanotesla sensitivity using nitrogen-vacancy diamond magnetometry. They then combined the measurements with simulations of nuclear spin procession to predict the corresponding MRI contrast.
“We demonstrate the utility of this technology in an in vitro model of macrophage iron uptake and histological samples from a mouse model of hepatic iron overload,” the study states. “In addition, we follow magnetic particle endocytosis in live cells. This approach bridges a fundamental gap between an MRI voxel and its microscopic constituents.”
According to the study, nitrogen-vacancy magnetometry is a relatively new technique that allows the imaging of magnetic fields with optical resolution using the electronic properties of fluorescent NV quantum defects in diamond.
With a closer examination of a smaller location inside the body, medical researchers can visualize the locations of inflamed tissues in a patient’s body by using an MRI to take images of immune cells called macrophages that have been labeled with magnetic iron particles. Macrophages take up iron particles injected into the bloodstream and migrate toward inflamed sites. The MRI signal is affected by the presence of iron particles, allowing the images to reveal the location of unhealthy tissue.
However, the exact level of MRI contrast depends on precisely how the cells take up and store the iron particles on the micrometer scale, which cannot be seen directly in the MRI images.
The new technique could provide a better understanding of how different iron distributions affects MRI contrast, as well as a better idea of the scope of inflammation.
The study was published in Nature Communications.
