Quality Test And Experimental Evaluation Of An Ultrasonography-guided Multi-channel Phased-array Focused Ultrasound System For Treatment Of Uterine Fibroids

Uterine fibroids are common benign tumors,which is induced by the proliferation of uterine smooth-muscle cells.This disease not only costs patients much but also has impacts on the quality of life.Gradually recognized by the clinicians,high-intensity focused ultrasound(HIFU)provides another noninvasive treatment option.Quality test and evaluation of ultrasound-guided focused ultrasound system should be performed before treatments.The following work is done for the quality test of the developed system.(1)Center frequency,delivered electric power and electro-to-acoustic efficiency of several transducers were measured;(2)For phased-array,phases and amplitudes of driving signals as well as resolution of pulse width were measured.Acoustic intensity distribution,focus location and size of focal zone for both geometric and steering foci were measured in comparison with theoretical values;focus and off-focus temperature elevations were measured as well.The results show that the electro-to-acoustic efficiency of the transducers is about 50%.The system has high resolution in generating phases with average deviations of-0.25°and 1.96°for terminals of the load and power amplifier respectively.The resolution of pulse width also satisfies the requirement since the average measured relative error is about3.9%.The phased array is capable of focusing as indicated by its focus deviation in orders of 0.1 mm and comparable focus size(0.8×0.8×11mm~3)with theoretical values(0.76×0.77×9.6 mm~3).In the experiments,two treatment cells respectively in diameter of 4and 8 mm were sonicated for ex vivo pork experiments.The results demonstrate the feasibility of the system to produce lesion ranges of 3.8×4.2 mm~2 and 7.5×8.4 mm~2.Pathological result of ex vivo uterine fibroids indicates that the system could produce necrosis in fibroids tissue.The in vivo rabbit experiment also verifies that the system is able to ablate tissue at given depths without skin burning,which demonstrates the efficacy and safety of the developed system.