The Technology

Tissue Destruction

Thermal Ablation

Thermal ablation uses high-intensity ultrasound energy to raise tissue temperatures to above 55°C, causing localised cell death while sparing nearby healthy tissue. Magnetic resonance imaging (MRI) or ultrasound guide the procedure, and MRI thermometry can provide real-time treatment monitoring and thermal dose control. 

In the UK, this approach is used to treat tumours in the uterus and prostate, as well as neurological disorders such as essential tremor and Parkinson’s disease.  

Click here to hear Professor Wady Gedroyc explain how thermal ablation is used to treat essential tremor at St Mary’s Hospital, Imperial College London.

Histotripsy

Histotripsy is a nonthermal method that uses tiny bubbles to mechanically destroy tissue with a high degree of precision. Short, high-intensity pulses generate cavities or microbubbles in the targeted tissue, and as these bubbles collapse, they produce shockwaves that mechanically disrupt cell membranes, effectively liquefying the tissue. This method minimises damage to surrounding structures and can be monitored in real time with ultrasound imaging. 

Histotripsy is under investigation globally for treating cardiovascular diseases and various cancers, including those in the liver, kidney, and soft tissues.  

Histotripsy is currently being used to treat liver cancer at Addenbrookes Hospital in Cambridge. Find out more here. 

Sonodynamic Therapy

Sonodynamic therapy uses focused ultrasound to activate sound-sensitive chemical agents (sonosensitisers) that accumulate in tumours. When exposed to ultrasound energy, these agents generate toxic free radicals that induce cell death. 

This method allows for deep tissue targeting and reduced damage to healthy tissue. It is currently under clinical investigation for brain tumours. 

Enhanced Drug Delivery

Blood-Brain Barrier Opening

The blood-brain barrier (BBB) is a tightly linked group of cells that protect the brain but prevent therapies from accessing it. Focused ultrasound, combined with intravenously injected microbubbles (MB-FUS), can temporarily and safely open the BBB. This enables larger molecules, immune cells, and gene carriers, to reach the brain for several hours post-treatment.  

This technique is under clinical evaluation for conditions like Alzheimer’s disease, and brain tumours, offering targeted therapeutic access previously blocked by the BBB. 

Localised Release of Therapies

Focused ultrasound can release therapeutics from encapsulated carriers like liposomes, microbubbles, and nanobubbles at targeted sites. These carriers circulate in the body but only release their contents when triggered by localised ultrasound, ensuring precise drug delivery with minimal systemic toxicity. This approach is being explored for cancer and neurological diseases. Real-time imaging tracks delivery, and ultrasound’s mechanical and thermal effects can further boost drug absorption in target tissues. 

Find out how Dr Eleanor Stride is investigating the use of microbubbles to deliver cancer treatment at the University of Oxford’s Institute of Biomedical Engineering. See the profile.

Neuromodulation

Modulation of Neural Activity and Nerve Fibres

Neuromodulation with focused ultrasound allows non-invasive stimulation or suppression of neural activity. Low-intensity ultrasound can reversibly alter brain or nerve function without causing tissue damage. This technique shows promise for treating neurological and psychiatric conditions like depression, epilepsy, obsessive-compulsive disorder (OCD), addiction, and chronic pain.  

Learn more about how brain stimulation is being used to target the symptoms of Lewy body dementia at our Oxford Centre of Excellence. Read the article.

Immunomodulation

Focused ultrasound can modulate the immune response either by releasing antigens or altering immune cell behaviour. While not always sufficient alone, the technology is under active investigation as a combination therapy to boost anti-tumour immunity, particularly in difficult-to-treat cancers with dense stroma or immune-suppressive environments. One current interesting area being explored is using focused ultrasound as a method to remotely and non-invasively activate CAR-T cells through thermal or mechanical gene switches with a view to reducing systemic toxicity.  

The following information is available from the US based Focused Ultrasound Foundation website (links will open in a new tab).

• Mechanisms of Action (further information) 
• Focused Ultrasound Timeline
• State of the Field