There is a new, non-invasive way to monitor blood flow in the brain. Scientists have created a soft, stretchable patch that can be easily worn, and uses ultrafast ultrasound to provide data on cerebral blood flow in three dimensions. This novel technology is a massive improvement on the current standard for monitoring brain blood flow, which is a transcranial Doppler ultrasound that requires a trained technician to perform. Since the current method needs a technician to continuously hold a probe against a patient's head, it is quite limited in its applications. Now, it will be possible to monitor cranial blood flow over the long term, and at different times of the day and night. The work has been reported in Nature.
"The continuous monitoring capability of the patch addresses a critical gap in current clinical practices," said co-first study author Sai Zhou, a graduate student in the lab of Professor Sheng Xu at the University of California San Diego Jacobs School of Engineering.
Zhou noted that cerebral blood flow is usually checked at specific times every day, which does not necessarily capture what might be happening the rest of the time, such as fluctuations. This new device could provide a warning about the onset of a stroke that may occur in the middle of the night, and the person can get help in time.
The new technology could also assist patients who may be having brain surgery, or recovering from it, added co-first study author Geonho Park, who is also a graduate student in the Xu lab.
The blood flow monitoring patch is only the size of a stamp, and is made from a stretchy silicone that has stretchable electronics embedded within it. There is a layer of tiny piezoelectric transducers that can receive and generate ultrasound waves, some of which are reflected from the brain. The system is capable of ultrafast ultrasound imaging, and captures thousands of images per second to produce robust data. There is also a layer of copper mesh that can minimize interference to enhance the signal, which is low because of the skull. Other layers contain stretchable electrodes.
The patch does have to be linked to a power source and computer with cables while it is being used. Images from the patch are processed after they are captured to produce 3D data on the sizes, positions, and angles of major arteries in the brain.
"The cerebral vasculature is a complex structure with multiple branching vessels. You need a device capable of capturing this three-dimensional information to get the whole picture and obtain more accurate measurements," explained co-first study author Xinyi Yang, who is also a graduate student in the Xu lab.
The investigators tested the patch on 36 healthy volunteers, and assessed its ability to detect blood flow velocity data in the brain's major arteries. During the tests, study volunteers performed various activities like breath-holding and reading, which can affect cranial blood flow. The data from the patch was found to align closely with the conventional measurement method - the handheld ultrasound probe.
The researchers are now planning to commercialize this technology with a company called Softsonics.
Sources: University of California San Diego, Nature