Experimental Study On Temperature Rise And Calculus Fragmentation By Ultrasonic Cavitation Induced By HIFU In Kidney Tissue-mimicking Phantom

Kidney stones may cause kidney blockage, infection and kidney failure.The focus of the thesis is the high intensity focused ultrasonic (HIFU) effectson stone fragmentation, as well as its thermal effect on tissue-mimickingphantom. An ultrasonic experimental system is set up with a mobile platformof5degrees of freedom. Kidney-mimicking phantom and groups of stonephantoms with similar mechanical and acoustic properties of theircounterparts in human bodies have been used for tests. High-speedphotography is used to record the process of cavitation bubbles’ activities on atissue-mimicking phantom basis. Meanwhile, a group of thermocouples arelaid to acquire the temperature distributions in the tissue-mimicking phantom,with1Hz frequency. Lastly,3D scanners is used to construct digital,three-dimensional models of stone phantom’s damage crators, and analyticalbalances is used to acquire stones’ mass losses. The main results are describedas following:1) Cavitation bubbles’ activities are different between in water and intissue-mimicking phantom. Tissue-mimicking phantom has damaged spots after acertain period of ultrasonic treatment.2) Focusing area has the maximum temperature rise within the HIFU acousticfield. Continuous Wave treatment results in a distinctive raise in temperature, whilePulse Wave treatment results in a slight raise in temperature.3) Increased ultrasonic intensity or treatment period may cause increase in thedepth and width of stone’s damage crators. Stones in agar gel have less loss (about50%) in mass than in water. This indicates that cavitation effect takes up apercentage about50%of the total ultrasonic effect on stone fragmentation.