Treatment Planning Of Scanning Time And Path For Phased High-intensity Focused Ultrasound Surgery

High-intensity focused ultrasound (HIFU) has received widespread attention in medical ultrasonic filed as an effective treatment method in tumors. Phased-array HIFU get beam focused by controlling the phase of input signal of each element on the array. Because of the agility and controllability of phased-array, it is widely researched recently. Our laboratory's phased-array HIFU equipment can form many different acoustic modes, which is made up of phased signal generator, treatment platform, phased arrays applicator, power amplifier system, C-arm and control unit.In HIFU surgery, the cumulated heat in non-target area will damage the healthy tissue. To avoid this, cooling time is intervened between sequential sonications to reduce the cumulated heat in healthy tissue. Cooling time between sequential sonications in the conventional heating method for HIFU surgery leads to long treatment time. In order to reduce treatment time, an unequal heating duration method, which means heating in long and short durations alternately without cooling time, is introduced in this paper. Three treatment plans, which are conventional method, unequal heating duration method in linear scanning and unequal heating duration method in spiral scanning, are compared through ablating the same area in simulation. To evaluate the treatment results, the finite element method (FEM) is employed to perform transient thermal analysis and thermal doses are calculated. With the unequal heating duration method, treatment time is reduced by more than 50 percent compared with the conventional method while the target necrosis rate is more than 97 percent. Simulation results show that the unequal heating duration method is effective and promising in HIFU.In order to verify the simulation results, we have developed a HIFU Management System for therapy planning and done some in vitro experiments. With the HIFU management system, doctors can make the therapy plans easily. At first, the doctor paints the border of the treatment area and determines the starting point in the area. Then, the computer works out the coordinate of each focus with the Bresenham algorithm and scan-line area-filling algorithm automatically. The results of the in vitro experiments verified the feasibility of the unequal heating duration method and the potential of phased array HIFU in clinical treatment.