Model-Based Treatment Planning for Focused Ultrasound Surgery

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Cancer is one of the most prevalent diseases in the UK. Each year it accounts for nearly 1 in 3 of all deaths. For patients with late-stage cancer, the cancer cells often spread to other parts of the body. This process is called metastasis, and the secondary tumours that form are called metastases. One of the most common sites for metastases to develop is bones. Around 2 in 3 patients with late-stage breast and prostate cancer, and 1 in 3 with late-stage lung, thyroid, and kidney cancer will develop bone metastases. This can cause debilitating pain, which has a significant impact on patients' quality of life. The most common treatment for reducing pain from bone metastases is external beam radiation therapy. This is aimed at relieving symptoms and controlling the growth of the cancer to improve quality of life, rather than trying to cure the patient (this is known as palliative care). However, as many as 1 in 3 patients treated with radiation therapy do not experience adequate pain relief, and the treatment cannot be repeated due to the toxicity of radiation to healthy tissue inside the body. A very promising alternative therapy for pain palliation is focused ultrasound surgery, also known as high-intensity focused ultrasound or HIFU. This technique works by sending a tightly focused beam of ultrasound into the tissue. At the focus, the ultrasound energy is sufficient to heat the tissue and cause cell death in a very localised region, while the surrounding tissue is not harmed. This is akin to focusing sunlight through a magnifying glass, where only in the focus is the energy high enough to singe an object. Focused ultrasound surgery can be used to alleviate the pain from bone metastases by treating the layer of nerves and connective tissue that surrounds the bone. The major challenge is to ensure the focus is accurately placed at the desired target within the body. This is difficult because bones and other organs can significantly distort the path of the ultrasound beam. The aim of this fellowship is to develop, validate, and apply new computer models to simulate how sound waves travel inside the human body. These models will be based on innovative advances in theoretical acoustics and numerical methods, and will use state-of-the-art computing facilities that have only recently become available. The computer models will allow the position of the focus and the heating of bones during focused ultrasound surgery to be accurately predicted for the first time. This will allow physicians to carefully plan and optimise the treatment parameters to eliminate the pain arising from bone metastases. This is expected to increase the effectiveness of focused ultrasound surgery, reduce the time it takes to treat patients, and extend the range and location of cancers that are eligible for treatment. As part of the fellowship, the models will be rigorously validated using patient data from previous clinical treatments, along with carefully planned laboratory experiments using phantom materials designed to mimic human tissue.