Principle of high intensity focused ultrasound

The current preferred method for curing tumors is still surgical resection. Advances in science and technology have led to the development of open surgery to a smaller trauma. Various interventional is minimally invasive treatment methods, including percutaneous radio frequency ablation and microwave coagulation,which have been widely used in the clinical practice. For decades, people have been expecting to achieve the non-invasive tumor ablation. As early as 1942, Lynn proposed the concept of high intensity focused ultrasound HIFU ceramic transducer. in 1958, which is used HIFU technology. In the experimental study of craniotomy for Parkinson's disease, it was found that the ultrasonic beam can produce a better focal region at the selected depth of the body to destroy the target tissue without damaging the adjacent tissue. In 1956, Burov first proposed the treatment of transient high-intensity ultrasound for a long time. Low intensity ultrasound irradiation is better in the late 1990s, Wang Zhisheng used HIFU for anti-early pregnancy, and was the first to use this technology for clinical treatment of liver cancer, breast cancer and other diseases.

The basic principle of HIFU:

Thermal effects: The currently recognized primary cause of killing or damaging cells is the local high temperature effect produced by HIFU. The critical temperature for inactivating tumor cells is 42.6 to 43. 0°C, while the normal cells are 45°C. Early thermotherapy is based on the histological hemorrhage defects of cancer and the different treatments of ultrasound and heat dissipation. The HIFU focused ultrasound beam not only has the same function, but also can reach the focus. The high sound intensity enables the sound energy to be quickly absorbed by the tissue and converted into heat energy. At a local instant, a high temperature of 70°C or higher is generated, and the tumor cells can be coagulated necrotic to achieve thermal ablation after the irradiation time is less than 1 s. HIFU ultherapy transducer found that 10 pig kidney and exfoliated renal cell carcinoma, HIFU can cause coagulative necrosis, dissolved necrosis, lytic necrosis and degeneration of tissue cells. Tissue necrosis has obvious pathological changes, and although the morphological changes are not obvious under light microscopy, the cells have lost their function and inhibited tumor growth. Mechanical effect refers to the high-frequency oscillation of the molecular structure of tissue cells subjected to ultrasound in the body. The mechanical effects of strong changes have mechanical effects,which cause cell lysis, functional changes, DNA macromolecular degradation and protein denaturation, and can cause intercellular viscosity coefficients, cell separation and shedding.