Abstract
High-intensity focused ultrasound (HIFU) is a non-invasive technique and widely used in medical and dental treatment for reaching and affecting deep seated tissues within the body, such as the removal of fat tissues under the skin, destruction of malignant tumour cells or target volume for the purpose of tissue debulking. This study aims to explore the damage characteristics of elastic material (regarded as soft tissue) by HIFU separated by a thin membrane all immersed in a water medium, in which the latter is used to mimic the human skin in medical treatments. Measurements of acoustic pressure along the vertical central line of HIFU transducer with and without this membrane were conducted and effects of membrane on the focal region were investigated. Results showed that the existence of the membrane serves primarily to reflect partial energy of incident ultrasound wave, and has no effect on phases of wave propagating in water. Next, Polydimethylsiloxane (PDMS) was selected as the elastic material for the experiments. The process of PDMS damage through the membrane by HIFU were recorded and the distribution of temperature around and within the ‘destroyed’ PDMS block was captured by an infrared camera. The very high temperature measured within the PDMS leading to the formations of cavity and crack within the PDMS block, can be attributed to the accumulation of the energy from the ultrasound source. Finally, the effects of PDMS with different elasticity on their damage characteristics are discussed.
Highlights
High-intensity focused ultrasound (HIFU) is widely used in medical treatments for therapeutic purposes.[1,2,3,4] Differing from common ultrasound that creates weak planar ultrasound waves, HIFU has a much higher power output or intensity at the focal point
This study has been focused on the damage characteristics of Polydimethylsiloxane (PDMS, an elastic material) through a thin membrane by HIFU on the burst mode
Some conclusions can be drawn: (1) Existence of the thin membrane above the HIFU transducer would not change the focal position of the transducer though there is a small reduction on the magnitude of acoustic pressure since only partial energy propagating from HIFU transducer is reflected by the membrane
Summary
High-intensity focused ultrasound (HIFU) is widely used in medical treatments for therapeutic purposes.[1,2,3,4] Differing from common ultrasound that creates weak planar ultrasound waves, HIFU has a much higher power output or intensity at the focal point. The ability to cause cell death in a volume of tissue distant from the ultrasound source makes HIFU an attractive option as a non-invasive surgical tool capable of selectively damaging deep seated tissues within the body.[5] When a HIFU transducer is placed in a water tank, the ultrasound wave produced in a focused manner can potentially cause the generation of cavitation bubbles in the fluid These bubbles, exhibiting complicated dynamic behaviours with other materials or tissues nearby,[6,7,8,9] can oscillate, expand and collapse with high speed jet in a few microseconds under the combined action of the fluid field and boundaries.[10,11,12,13,14,15,16] This high speed jet could be used beneficially, such
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