Follow the flow
The brain’s venous system has long been difficult to study. But a Berkeley-led team has developed an innovative MRI technique that may expand our understanding of this critical system and improve disease diagnosis.
Their method, Displacement Spectrum (DiSpect) MRI, maps blood flows “in reverse” to reveal the source of blood in the brain’s veins. Like some MRI methods, DiSpect uses the water in blood as a tracing agent to map blood flow in the brain. The water’s hydrogen atoms possess a quantum mechanical property called spin, and these can be magnetized when exposed to a magnetic field, like an MRI scanner. But what makes DiSpect unique is its ability to track the “memory” of these nuclear spins, allowing it to map blood flow back to its source.
“We can tag information onto spins in the blood, knowing that they store that information for three, four, five seconds, or so,” said Michael Lustig, professor of electrical engineering and computer sciences. “In that time, the tagged blood will have traveled, draining from the brain’s capillaries and smaller veins into larger veins. And when we image it at the larger veins, we can decode the information to determine where it came from.”
DiSpect may prove useful in shedding light on basic neuroscience questions tied to neurovascular coupling, the mechanism by which blood flow changes in response to neuronal activity, said electrical engineering and computer sciences professor Chunlei Liu.
The method could also be used to develop more effective strategies for treating vascular and neurological conditions, such as arteriovenous malformations, which are bundles of abnormally formed blood vessels. Currently, clinicians must spend hours inserting a catheter and contrast into each tiny artery to identify which one is feeding the malformation.
“DiSpect could provide a no-contrast, non-invasive and less risky detection method,” said postdoctoral researcher Ekin Karasan. “Starting at the veins that are draining this malformation, we could use reverse imaging to identify which artery the blood is coming from — [and] then figure out whether intervention is required.”
Learn more: New MRI method offers deeper insight into brain physiology; MR perfusion source mapping depicts venous territories and reveals perfusion modulation during neural activation (Nature Communications)