一种用于脑神经刺激的程控超声发生器

摘要

Low intensity ultrasound can stimulate brain tissues.We designed a programmable ultrasound generator for brain stimulation.From a computer the generator receives the stimulate variables,based on which an embedded FPGA chip generates the stimulation pulses.The output power is controlled by setting the duty cycle of the power amplifier at the last stage,which works in switching style for high efficiency.An impedance matching network is inserted between the output terminal and the ultrasound transducer so that the rectangular waveform is transformed to sine.The variables of the pulses are easy to understand and adjust compared to those of the general-purpose functional generators because they are designed especially for brain stimulating.The highest ultrasound frequency of the generator is 2MHz and the maximum output power is more than 157.1 watts.Twelve SD rats were experimented with the generator and a home-made 500kHz transducer,when rat brains were stimulated under the condition of spatial-peak temporal averaged intensity Isppa =5.36W/cm2,90％ success rate was achieved in terms of the responsive muscle contracting.The test results and animal experiments show that the generator we designed is capable to be used in the research work of brain stimulation.%低强度超声对大脑具有明显的刺激作用.设计一种用于脑刺激的程控超声发生器,接受计算机发出的刺激参数信息,内置的可编程门阵列(FPGA)根据这些信息发生刺激脉冲串,并通过改变功放管驱动占空比的方法控制输出功率.发生器采用开关型功放保证效率,通过阻抗匹配电路将输出方波转换成换能器上的正弦波.发生器的脉冲序列参数根据刺激波形设计,相对于使用通用函数发生器更容易理解,且调节方便.测试表明,发生器的最高超声频率可达2 MHz,最大输出功率157.1 W.配接自制的500 kHz聚焦换能器,在空间峰值脉冲平均声强Isppa=5.36 W/cm2的条件下,对12只大鼠的脑部进行刺激,以肌肉收缩为指标进行观察,刺激成功率达到90％.测试结果和动物实验证明,该发生器适合超声脑刺激研究之用.