Last May, MIT acquired its first 3 Tesla Siemens MRI machine for noninvasive imaging of the human brain, located in the Martinos Imaging Center at the McGovern Institute. This spring, a new, more powerful scanner moved in next to it, thanks to a gift from an anonymous donor. This scanner, a 9.4 Tesla Bruker magnet with a small (20 cm) bore, will be used for rodents and small primates, as well as live cell cultures and chemical preparations. It will help researchers make direct links between molecular and genetic techniques and live animal studies, and between animal studies and human studies.
"We're very grateful to our donor and to Bruker for helping bring this advanced imaging technology to all of MIT," said Robert Desimone, director of the McGovern Institute. "Now that the two MRI machines are just steps apart on our campus, we can move back and forth between human and animal studies much more easily. The 9.4T magnet will also be a new focal point for technology development on campus, including the development of new imaging agents."
Previously, researchers who wanted to work at this cutting-edge field strength had to carefully transport their experiments to the Charlestown campus of Massachusetts General Hospital (MGH) to conduct studies on a 9.4T machine there. Transportation was time-consuming and difficult, remembers Christopher Moore, a principal investigator in the McGovern Institute and assistant professor in the Department of Brain and Cognitive Sciences.
Getting the scanner to campus, and getting it up and running, has been a broad effort. Moore, working with Alan Jasanoff, an associate member of the McGovern Institute with appointments in nuclear science and engineering, biological engineering, and brain and cognitive sciences, did the groundwork in determining the specifications needed for making the machine maximally useful to the broader community while meeting the needs of each of their laboratories. In addition, many colleagues and collaborators at the Martinos Center at MGH helped train Moore and his laboratory in use of the 9.4T scanner, and provided invaluable help and advice in acquiring the scanner at MIT. Once the machine arrived, Steve Shannon and Christina Triantafyllou in the Martinos Imaging Center at the McGovern Institute, and other members of the Moore and Jasanoff laboratories, provided much of the expertise to put the machine on line. Moore will jointly oversee the MIT 9.4T scanner with Jasanoff.
After a trial period for the magnet throughout the summer, the scanner will be opened up to researchers in the community. "We hope it will facilitate a broad range of interdisplinary work in neurodegenerative diseases, systems neuroscience, developmental biology, cancer research, and new imaging technologies," Desimone says.
Tesla refers to the strength of the magnet, and the stronger the magnetic field, the finer the resolution of the image. The Martinos Imaging Center's 9.4T can resolve MRI signals down to 50 microns, smaller than the dot at the end of this sentence, and small enough to reveal differences among small clusters of neurons.
Researchers will mainly use the machine for live animal studies. For example, Moore will use it to investigate somatosensory processing in the primate brain. He has already demonstrated the magnet's power to pinpoint brain regions in New World monkeys never before known to be involved in tactile sensation. He was then able to determine that the analogous region of the human cortex also has this unsuspected function. Moore says this study exemplifies how animal studies can be used to gain new insights into the human brain. Moore is also preparing to use the powerful capability of this scanner to track blood in the brain, to test new hypotheses that vascular signals play a role in information processing.
For his animal studies, Jasanoff plans to focus on a classic paradigm of reward behavior in awake and behaving rats, examining patterns of neural activity across the entire brain. He is also collaborating with Susan Lindquist at the Whitehead Institute to do live imaging on mouse models for neurodegenerative diseases.
The scanner can also facilitate cellular, molecular and chemical studies, Jasanoff emphasized. For example, his laboratory is developing MRI contrast agents to apply to next-generation functional imaging, allowing him to observe neural functions with molecular specificity. He and his collaborators across MIT will use the 9.4T magnet to test properties of their newest imaging agents in cell and tissue culture. They have already developed an agent that detects calcium, which flows into cells as neurons fire, and are working on other indicator molecules for monitoring changes in neurotransmitters such as dopamine and serotonin, which are important for the control of motivation and emotion.
Jasanoff anticipates that researchers will integrate high-resolution MRI studies using the molecular imaging agents with a wealth of other imaging techniques, such as optical imaging in mouse models for human disease.
"New imaging tools are opening up the exploration of 'inner space' in the brain," Desimone said, "in much the same way that the telescope revolutionized our understanding of outer space."