Modeling And Experimental Study Of Lesion Formation Induced By High Intensity Focused Ultrasound Along A Spiral Path In Continuous Scanning Mode

High intensity focused ultrasound(HIFU)has made rapid progress in the clinical application of tumor therapy.In this technology,the scanning mode of HIFU transducer has an important effect on the thermal lesion formation in the treatment.In this thesis,the theoretical simulation and experimental study were used to study the temperature distribution and lesion formation caused by HIFU in continuous scanning mode along a spiral path.Theoretically,the thermoacoustic coupling model based on the KZK equation and the Pennes biological heat transfer equation was used to predict acoustic field generated by HIFU,then the lesion formation model based on the thermal dose were employed to predict the temperature field distribution and lesion formation of HIFU treatment.In the experiment,the HIFU experiment with gel and ex vitro bovine liver samples was carried out.The grid spacing of the spiral path and scanning speed were set as the control variable to compare the lesion formation,and the shape of lesion and treatment efficiency were assessed as a function of grid spacing and scanning speed.The results show that the continuous scanning mode using the spiral path has the potential to efficiently produce uniform lesions to cover the target area completely.The complete coverage of the entire treated volume can be achieved as long as the spacing grid of the spiral pathway is small enough for heat to diffuse and deposit,and the treatment efficiency can be optimized by selecting an appropriate scanning speed.This study can provide guidance for further optimization of the treatment efficiency and safety of HIFU therapy.