Research On Acoustic Field Detection Of Focused Ultrasound Combined With Infrared Thermal Imaging

In the research of HIFU with array,the acoustic field distribution characteristics,such as the location and dimension of the focus,focal region size and side lobe level,are the key factors that affect its safety and performance.When we evaluate performance in the practical measurements,existing methods used to measure focusing transducer's acoustic field must have to execute three-dimensional scan to get the right position of the focus,then do further scanning and calculating to achieve the accurate parameters of acoustic field.Consequently,the current standard with hydrophone method is a high time-consuming method,and this method cannot describe some key phased characteristics as deflection characteristic of transducer or transducer arrays for a great diversity of those transducer or transducer array.A new method is proposed to measure HIFU ultrasound field recently with the help of infrared thermal imaging technique,by measuring thermal effect on the surface of ultrasound absorber.Based on this thought,this thesis has proposed a method combined with infrared thermal imaging to detect the acoustic field characteristics of focused ultrasound.Taking advantage of such features as handy-acquisition image,fast-imaging and wide-range temperature of infrared thermal imaging,this method uses infrared images to locate the right location of the focus during the measurement of standard hydrophone method.Using infrared camera to scan once along the acoustic axis,the temperature distribution of those preset plane in acoustic field can be acquired,then switch to hydrophone mode to measure the accurate parameters with the help of location information from infrared images,shortening the measurement time of the traditional hydrophone measurement method effectively.A measurement system is conceived to verify the feasibility of the detection method proposed in this paper,which is designed with two measurement mode: infrared mode and hydrophone mode,and they can be easily switched at any time.The key point of the sound field measurement combined with infrared thermal imaging is the design of ultrasonic absorber.The influence of acoustic and thermal parameters of ultrasonic absorber is simulated and analyzed.The sound field measurement of the small animal HIFU system was carried out with the method described as acoustic field detection combined with infrared thermal imaging in this paper.The results and measurement time of infrared thermography and hydrophone were compared and analyzed.The analysis of calculation and experimental results show that the proposed method can effectively improve the measurement efficiency of the standard hydrophone measurement method and characterize the sound field from the thermal aspect,which is of great significance for the standardization of the focused ultrasonic sound field measurement technology.