New, incredibly detailed videos capture how the brain jiggles inside the skull as blood and other fluids flow through the squidgy organ. In two new studies, published May 5 in the journals Brain Multiphysics and Magnetic Resonance in Medicine, scientists employed a brain-scanning technique often used to capture static, 2D images of organs to instead create 3D videos of the brain moving in real-time. The brain tissue can be seen pulsating in reaction to blood rushing through its blood vessels and cerebrospinal fluid (CSF), a clear liquid that carries nutrients and cushions the brain, flowing in and around hollow spaces in the organ. The new videos "amplify" this motion in the brain, exaggerating the movement so it can be easily analyzed. For this reason, the new technique is called "3D amplified magnetic resonance imaging," or 3D aMRI. "Really, it's a very small motion," typically between about 0.002 inches and 0.015 inches (50 to 400 micrometers) at most, in terms of how far the tissue deforms, said Mehmet Kurt, an assistant professor in the Department of Mechanical Engineering at the Stevens Institute of Technology in New Jersey, adjunct professor at the Icahn School of Medicine at Mount Sinai in New York and co-author on both studies. Making the movements appear about 25 times larger allowed the researchers to assess that motion in greater detail, tracking its direction and amplitude with precision. The new scanning technique could someday prove useful in the diagnosis and treatment of medical conditions in which fluids get blocked from flowing through the brain. One such condition is hydrocephalus, in which excess fluid builds up in the cavities of the brain, said Samantha Holdsworth, a senior lecturer at the University of Auckland in New Zealand, research director at Mātai, a New Zealand research center with a focus on medical imaging, and co-author on both studies. "We've got a lot of work to do to really prove its clinical application … but that's the nature of all new technology," she said. "We're just sort of at the beginnings of what can be achieved." Capturing the brain in motion To create the new scanning technique, the team started with basic MRI, which uses strong magnets to apply a magnetic field to the body. In response, the hydrogen nuclei within water molecules in the body all line up with this magnetic field. The scanner then releases a radio-frequency current that stimulates the hydrogen nuclei, causing them to pull out of alignment. When that radio-frequency current switches off, all of the nuclei snap back into position, but they do so at different rates depending on what kind of tissue surrounds them. Each nucleus releases a radio signal when it pops back into alignment, and the machine picks up this signal and uses it to create an image. By applying multiple magnetic fields to the body, MRI can also be used to create 3D images, which can be viewed from multiple angles, Live Science previously reported. Back in 2016, Holdsworth and her colleagues built upon this base MRI technology to create aMRI. In essence, the method involves stitching together a series of MRI images captured at consecutive points in time to create a short movie, while also amplifying the subtle movements captured in each frame, the team wrote in a 2016 report in Magnetic Resonance in Medicine. However, at first, aMRI could only be used to track motion within a single plane — for example, as viewed from the side or the top of the brain, but not from several angles at once, Holdsworth said. Now, they've extended the technique to capture three dimensions simultaneously. "A 2D version of this was incomplete, from a biomechanical perspective; it was an incomplete expression of what was happening," Kurt said. "It might be crucial from a diagnostic perspective" to be able to evaluate the motion from all angles, he said. Several other MRI techniques can also be used to track motion in the brain — namely, Displacement Encoding with Stimulated Echoes (DENSE) and phase-contrast MRI, Holdsworth said. However, "the advantage of the amplified MRI is that you can see the motion in relation to the underlying anatomy, which is this really exquisite anatomy," she said. While the other methods capture a somewhat fuzzier picture of the brain with poorer temporal resolution, 3D aMRI can produce real-time footage of the brain at an impressive spatial resolution of 0.00007 cubic inches (1.2 cubic millimeters). The researchers are now using their technique to study Chiari I malformation (CM-I), a condition in which part of the brain pushes down through the hole at the base of the skull where the spinal cord passes through. In collaboration with Mount Sinai, Kurt is also studying hydrocephalus in newborn babies, scanning their brains before and after corrective surgery. In addition, he is using a modified version of the scanning method, called aFlow, to study aneurysms, where the wall of an artery weakens and bulges out. Monitoring for distinct changes in blood flow may help doctors predict when an aneurysm might rupture, Kurt said. In New Zealand, Holdsworth is scanning the brains of patients with concussions, to see whether common patterns emerge in how fluid flows through their brains after injuries. Her group also plans to study whether aMRI could be used to indirectly measure pressure in the brain, because currently, the direct measurement requires drilling a small hole in the skull, Holdsworth said. Pressure in the brain can increase for many reasons, including traumatic injuries, tumors, infections and aneurysms; and in people with a condition called idiopathic intracranial hypertension, the exact cause of the pressure buildup is unknown, but it can trigger symptoms similar to those of a brain tumor, according to Cedars-Sinai. "There are so many questions to answer," Kurt said. "The opportunities are really endless." Source
