A team at Washington University in St. Louis, led by Dr. Hong Chen, has developed a new method to accurately measure the dose of drug delivered by focused ultrasound. This work, published recently in Scientific Reports, represents a huge step forward in safely and repeatedly delivering drugs across the blood-brain barrier.
In order to accurately quantify the amount of drug in a particular region, traditional methods rely on positron emission tomography (PET) imaging combined with radio labeled nanoparticles. The nanoparticles are administered to the patient at the same time as the drug of interest and act as markers, lighting up on the PET image and allowing researchers to measure where and how much of the drug was delivered. However, this procedure is expensive and involves exposing patients to radiation, and therefore isn’t ideal for repeated use.
Chen’s team explored whether an ultrasound technique called passive cavitation imaging (PCI) could be used instead. Drug delivery with focused ultrasound relies on the use of intravenously administered microbubbles – commonly used for contrast enhanced ultrasound imaging – to pump drugs from the blood stream into the surrounding tissue. The microbubbles respond to focused ultrasound beams by expanding and contracting as the pressure wave passes through the treatment area. This microbubble oscillation produces tiny sound waves that can be picked up by PCI and translated into a map of where and how many microbubbles are in the treated tissue. Chen’s team correlated PCI and PET imaging, and found that PCI was able to produce an accurate plot of drug dose throughout the targeted area. Termed "cavitation dose painting," this technique permits quantitative measurement of drug delivery without the need for expensive PET scans.
The National Institutes of Health has awarded Chen a $1.6 million grant to work on combining PCI with focused ultrasound and intranasal drug delivery.
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