Vienneau, Emelina P.; Weeks, Abbie E.; Pan, Ying-Chun; Shema, Peggy M.; Morgan, Victoria L.; Byram, Brett C. (2026).听.听IEEE Transactions on Biomedical Engineering.听
Functional ultrasound imaging (fUSI)听is a technique that measures brain activity by tracking changes in blood flow. Until now, using it in adults without contrast agents (special dyes) has been very limited, because the skull blocks and distorts ultrasound signals. In this study, researchers demonstrate a听proof-of-concept听method for performing fUSI through the intact adult skull, called听transcranial fUSI (tfUSI).
To make this possible, they used several improvements to boost image quality, including specialized signal coding to enhance sensitivity, motion correction and head stabilization to reduce movement effects, and advanced filtering to separate blood flow signals from background tissue noise. They tested the method in 13 healthy adults by asking them to alternate between normal breathing and听breath holding, which temporarily changes brain blood flow. Using this setup, they measured听cerebral blood volume听(the amount of blood in the brain) and found that the ultrasound signals closely tracked both the breathing task and changes in oxygen levels in the blood.
They also observed a delayed increase in blood flow (called听vasodilation) after breath holding, which matches known physiological responses. Overall, the results show that tfUSI can successfully measure brain blood flow changes through the adult skull without contrast agents. This opens the door to future use of this technology for studying brain activity and function in a noninvasive way.
