Research on Focused Ultrasonic Transducer in HIFU Technology

High-intensity focused ultrasound (HIFU) technology is originated in the 1940s. It is a certain way to make the ultrasound accumulate on the lesion tissue after passing through the body surface. After the interaction between the cells and the ultrasound in the lesion tissue. Producing irreversible coagulative necrosis for therapeutic purposes. This technology has attracted the attention and many scholars, doctors and patients at home and abroad for its non-invasive, harmless, safe and effective advantages. At present, HIFU technology has been widely used and promoted in the fields of urology, oncology, neurosurgery, gynecology, ophthalmology and other medical fields.

The core component of HIFU piezo ceramics technology is an ultrasonic focusing transducer, whose task is to convert electrical signals into ultrasonic signals, in a certain way, the ultrasonic energy is highly concentrated in the lesions, forming a high focused ultrasound energy to eliminate the lesions. HIFU technology is applied to living organisms. High-intensity ultrasound energy is used to eliminate the lesions during the treatment, but it is more important to ensure the safety of the treated objects. Therefore, the precise focusing of ultrasonic energy is the focusing characteristics of the ultrasonic transducer. It is key to HIFU technical treatment. Commonly ultrasonic transducers are generally made of piezoelectric ceramics, piezoelectric composite materials, etc. These materials have piezoelectric effect and inverse piezoelectric effect, which can realize the conversion of acoustic energy and electric energy, and functions of ultrasonic transducers.it is analogous to the principle of optical focusing, there are three ways to achieve ultrasonic focusing piezo,it is concave spherical self-focusing, mirror focusing, and acoustic lens focusing.

All three ultrasonic transducers can achieve the focusing of ultrasonic energy under certain conditions. Concave spherical self-focusing is active acoustic focusing, acoustic lens focusing is an auxiliary acoustic focusing, and reflective focusing is passive. In recent years, researchers have put together a number of small piezoelectric ceramic sheets, which combine electronic focusing with acoustic focusing to achieve ultrasound focusing through electronic phase modulation. This type of focusing is called electronic phased focusing. In the HIFU ultrasound piezo ceramic technology,it is concave spherical self-focusing, acoustic lens focusing and electronic phased array are used for focusing.The advantage of the concave spherical self-focusing transducer is that it can be adjusted according to the different depths of the lesion. It is usually a mechanical scanning method when is working. It is a simple and often used for focusing transducer.The acoustic lens focusing system can achieve focal length which changes according to clinical requirements, and has advantages in the case of small sound source size requirements and superficial lesions. Phased array focus transducers use electronic transducers to achieve ultrasound focusing by using ultrasonic transducer array probes. The advantages of Ultrasound HIFU piezo are that is no mechanical movement and fast scanning speed, it is high accuracy. depending on the size and position of the tumor. Setting the focus mode has strong practical value in clinical treatment; the disadvantage is that the electronic control circuit is large and complex, which limits its development and application to a certain extent.