Research On Ultrasonic Non-invasive Temperature Measurement At The Edge Of Thermal Ablation Of Ex-vivo Liver Based On Pyroelectric Effect

The treatment of liver tumors has always been the focus of medical research at home and abroad.As a new and minimally invasive method,thermal ablation can achieve the same local treatment effect as tumor resection surgery,so it is widely used in clinical treatment.However,in actual clinical surgery,there is no suitable method to monitor the temperature of the edge of the ablation area,and the operator cannot judge whether the temperature of the edge of the ablation area has reached the surgical requirements.As a result,the actual ablation range is often smaller than the size of the tumor and cannot completely kill the tumor.Cells affect the treatment effect.Therefore,it is of great significance to study a method for monitoring the temperature of the ablation zone.Ultrasonic temperature measurement methods are cheap and high in real-time,and have always been a research hotspot in medical non-invasive temperature measurement.This paper proposes a temperature measurement method that uses a pyroelectric sensor to measure the change in the acoustic attenuation coefficient of the tissue to be tested during the ablation process to obtain the temperature change at the edge of the ablation zone.This method will not be affected by ultrasonic scattering,refraction,etc.,and has higher temperature resolution and faster measurement speed than ultrasonic temperature measurement methods such as ultrasonic sound velocity method,nonlinear coefficient method,and scattering method.The specific content and results of this article are as follows:1 Established the "ultrasound-biological tissue-pyroelectric sensor" temperature measurement model,used COMSOL simulation software to perform multi-physics simulation on this temperature measurement model,and obtained the sound attenuation coefficient of the tissue during ablation and the output of the pyroelectric sensor The peak voltage is inversely proportional.Simultaneously,a simulation of the thermal ablation process of the liver was performed,and the law of the temperature change of the liver during ablation was obtained.Theoretically proved the feasibility of using pyroelectric sensors for ultrasonic temperature measurement.2.Designed and manufactured a pyroelectric sensor to measure the change of ultrasound power during ablation.The reliability of the sensor when measuring the ultrasonic power is tested:in the repeatability experiment,the error is within 2%,which proves a good stability;the sensitivity is 3.305 m V/W,which proves a good sensitivity.Experiments have proved that the ultrasonic power is proportional to the peak value of the output voltage of the sensor,which proves that the sensor can be used to measure the size of the ultrasonic power.3.Through the temperature measurement experiment on beef livers of different thicknesses after heating in a water bath,the "thickness-temperature-pyroelectric signal" function is obtained to estimate the temperature.The experiment proves that the estimated temperature is consistent with the temperature measured by the thermocouple.The error is within 2 ℃.4.Temperature measurement experiment of isolated liver ablation.First,use thermocouple to measure the temperature at a specific location during liver ablation to obtain the temperature change during ablation,and then use a pyroelectric sensor to measure the temperature of the ablation edge,and the error is within 4 ℃.It is proved that the temperature measurement method proposed in this paper can accurately measure the temperature of the edge of the thermal ablation zone.