Analysis And Measurement Experimental Research On Phased-Array Focused Ultrasonic Field

High intensity focused ultrasound (HIFU) has received widespread attention in medical ultrasonic filed as a noninvasive and effective treatment method in tumors. The main focusing methods used at present are self-focusing method, lens-focused method and ultrasound phased arrays. Different from the first two type focusing methods, phased-array focused ultrasonic system use several small elements to inlay in Focusing probe. The system get focused beam by controlling excitation signal phase of every element. Because the agility and controllability of system, it is widely researched and applied in focused ultrasound. Distributions and acoustic parameters of HIFU Field are not only the key part of the system, but also an important index to safety and validity of a HIFU therapy facility. The capability and effect of HIFU have a tight relationship with the acoustic field distributions. So the measurement of HIFU acoustic field is the significant part of focusing ultrasonic transducer researching. Our laboratory's phased-array HIFU equipment with a concave spherical surface can focus in many modes by the controlling algorithm. Meanwhile we have done some experiments in vitro and get good results. This paper mainly discussed and researched the acoustic filed of this transducer at theory analysis and experimental measurement aspects , meanwhile calculated the acoustic parameters.Firstly, the theory acoustic field distributions of this phased-array HIFU were simulated by pseudoinverse matrix algorithm with MATLAB tool. The side lobe size and position were analyzed when the focus was controlled in beam axis direction and focal plane and when opening different numbers of the array rings.Secondly, this paper described an acoustic filed measurement system based on LabVIEW platform, which is used to measure the acoustic pressure field distributions of the phased-array focused ultrasound transducer with a probe hydrophone scanning the acoustic field. The system can acquire acoustic pressure waveforms and Peak-Peak values distribution, signal analysis, distribution showing in graph and parameters calculation, etc.This paper exploring studied the measurement method of phased-array HIFU acoustic field and the experiment results were satisfied. Finally, we compared with the experimental and theoretical results. The experiment demonstrated feasibility and validity of the measurement system. The research on phased-array HIFU acoustic field measurement has a very important significance in the implementation and construction of therapy plans and analysis of real acoustic field.