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New nanoscale MRI machine breaks multiple world records

The Olympics are still a few weeks away, but researchers at Leiden University’s Institute of Physics are already smashing world records — if not Olympic ones — with a new nuclear magnetic resonance (NMR) microscope. In an effort to capture 3D images in atomic resolution, PhD students Jelmer T. Wagenaar and Arthur de Haan created the device to be 1,000 times more sensitive than similar microscopes and function at temperatures nearing absolute zero.

NMR is the principle behind MRI machines, which enable physicians to peer through our skin and examine our anatomy with minimal or no invasiveness. As electrically charged, atomic nuclei within our bodies spin around, they generate their own infinitesimal magnetic fields. When a patient places her arm in an MRI machine, the machine’s magnetic field causes the atoms’ nuclei to line up, while specific radio waves induce some of those nuclei to flip on their axes, until the radio signal is turned off and the nuclei return to their original state. The movement of these nuclei generates waves that depict the location of the atoms, allowing physicians to generate an image of the inside of the body.

“The higher the temperature, the more the atoms will move a little bit,” Wagenaar told Digital Trends. “It is like taking a photo — when somebody moves very fast, the photo gets a bit blurry. But the more that somebody sits still, the sharper the image. At zero Kelvin, the atoms do not move anymore, so the closer you work at zero Kelvin, the better it is to obtain sharp images.”

Leiden University researcher's NMR microscope, which consists of a thin wire and a small magnetic ball (here, colored purple). The ball causes a uniform magnetic field that induces the surrounding atomic nuclei to line up in the same direction. The researchers send radio waves through the sample, and cause some nuclei to flip in the opposite direction. By measuring the time until the nuclei flips back again, they can generate an image from the atoms' positions.

The Leiden University physicists’ NMR microscope consists of a thin wire and a small magnetic ball (here, colored purple). The ball causes a uniform magnetic field that induces the surrounding atomic nuclei to line up in the same direction. The researchers send radio waves through the sample, and cause some nuclei to flip in the opposite direction. By measuring the time until the nuclei flips back again, they can generate an image from the atoms’ positions.

Leiden Institute of Physics

At room temperature, only about 0.0001 percent of the nuclei’s spins will align, according to Wagenaar. “The rest behave random[ly],” he said. And since the microscopes can only detect aligned spins, this can only generate a vague image. “By decreasing the operating temperature to 42 miliKelvin, we achieved a three-order magnitude higher percentage of aligned spins.” In other words, the team’s device proved to be 1,000 more sensitive than current NMR microscopes. The team published its work in a study last week in the journal Physical Review Applied.

The work is far from over though, as the physicists have set their sights on medical applications. “The holy grail here is 3D imaging biological tissues with atomic resolution,” Wagenaar said. By capturing images in this sensitivity, Wagenaar thinks physicians can image proteins without damaging or disturbing the way they’re folded, which may offer new insights into diseases like Alzheimer’s and Parkinson’s at the molecular level.

“The development of a total new imaging technique takes a lot of time,” Wagenaar admitted, in a nod to the slow development of this type of technology from its conception in the 1990s until today. “The next couple of years our group is planning to obtain a nice image of a biological sample, and I hope that within a decade our technique can really contribute in understanding the misfolding of proteins on the atomic scale.”