International Brain Tumour Awareness Week
Saturday, 24th October to Saturday, 31st October 2020
Ultrasound-induced BBB disruption
In recent years, low-intensity focused ultrasound (FUS) has been proposed as a safe and reversible approach for opening the blood-brain barrier (BBB). There is a lot of interest in whether FUS can be used to improve the delivery of chemotherapy to brain tumours.
Initially, FUS alone was used to disrupt the BBB, but the large amount of energy required could lead to tissue damage. Current studies now inject pre-formed microbubbles through the bloodstream before FUS, as this reduces the amount of energy needed.
The injected microbubbles expand and contract (in a process called ‘cavitation’), which puts pressure on the blood vessels, forcing small openings to appear in the vessel walls. This temporarily opens the BBB in a non-invasive, safe and targeted manner, during which time a higher amount of drug can enter the brain. The BBB can stay open for up to four hours after treatment.
The procedure is usually guided by magnetic resonance imaging (MRI) to focus the ultrasound beams on the target with high accuracy. Disruption of the BBB can also be monitored with MRI, and positron emission tomography (PET) can be used to measure how much drug has been delivered to the brain.
This procedure has been shown to enhance the delivery of a large variety of therapies into the brain, from small molecular weight drugs, to monoclonal antibodies and cancer-targeting cells.
Two systems currently in clinical trials are the ExAblate® 4000 system (InSightec, Haifa, Israel) and the SonoCloud® device (CarThera, Paris, France).
CarThera video on YouTube.