Ultrasound technique monitors drug dose, delivery site in brain

A new ultrasound method called passive cavitation imaging (PCI) can create an image estimating the amount of a drug that has crossed the blood-brain barrier (BBB), according to new research conducted at Washington University in St. Louis.

The novel method monitors the behavior of microbubbles which help amplify the effects of ultrasound waves as the microscopic bubbles open a localized spot in the BBB for targeted drug delivery, according to Randy King, PhD, director of the program in ultrasound at the National Institute of Biomedical Imaging and Bioengineering (NIBIB).

“Researchers are developing non-invasive approaches using microbubbles and focused ultrasound waves to disrupt the blood-brain barrier (FUS-BBBD) briefly,” King said in a prepared statement. “As new techniques are established to permeate the BBB, we need complementary methods to monitor the delivery of treatments to ensure they are safely delivered to the site(s) of brain disease.”

King and colleagues labeled nanoparticles with a radioactive tracer, injecting them into the bloodstream of a mouse model following focused-ultrasound treatment in order to track the amount and location of the drug delivered. Using PET/CT imaging the scientists could measure and visualize the exact amount and location of the material in the brain.

Results showed a “pixel-by-pixel correlation between the PET and PCI images,” said Hong Chen, PhD, assistant professor of biomedical engineering and radiation oncology at Washington University in St. Louis.

The team noted bypassing PET/CT reduces radiation exposure to patients and can significantly reduce imaging costs compared to PCI, the researchers noted. 

“With our new technique, we can predict exactly where a drug will go and how much of it will be released when it gets there,” Chen explained. “It helps us to minimize a drug harming healthy parts of the brain and avoid ineffective treatments when not enough drug reaches the intended target.”

The study was first published in Scientific Reports.