兔尿道瘢痕超声治疗仪的设计与实现

Design and implementation of ultrasound therapy device for rabbit urethral scars

目的设计一台专用于兔尿道瘢痕的超声治疗仪,旨在验证此仪器的适用性及有效性。方法以新西兰雄兔为实验对象,针对其阴茎结构与尺寸对超声治疗仪进行特制,此超声治疗仪包括超声脉冲发射与控制系统、末级功放和超声探头。首先,针对兔阴茎尺寸及结构对超声探头进行设计,并通过COMSOL有限元仿真以及声场分布实际测试等确定超声探头的参数;其次,根据超声探头元件参数设计其驱动电路;然后,设计基于现场可编程门阵列(FPGA)和串口屏的超声脉冲发射与控制系统;接着,对整体完成的超声治疗仪进行整体性能测试和安全测试;最后,构建兔尿道重建模型,将8只白兔随机分为模型组和实验组,实验组立即接受该超声治疗仪对其尿道部位的治疗,参数设置为超声频率2 MHz,脉冲间隔10 ms,输出声强0.73 W/cm^(2)。治疗频率为2次/周(周二、四),每次照射10 min,持续4周;模型组则不接受任何治疗,用Image J软件对兔尿道组织中转化生长因子-β1(TGF-β1)、基质金属蛋白酶-2(MMP-2)和肿瘤坏死因子-α(TNF-α)染色阳性区域的面积占比进行定量分析,并计算尿道周长。结果添加了吸声材料的结构治疗腔内声压分布较为均匀,驻波比均值为1.11,结构设计满足设计期望。整体性能测试中3枚超声换能器自然焦点位置均为10 mm,声场分布一致性满足实验要求。各换能器峰值声压与电源电压关系接近线性。输出声强范围为0.35~0.74 W/cm^(2),满足实验要求。随着超声输出,测试点温度缓慢升高,此实验最高可使组织温度升高3.3℃,不会导致组织热损伤发生。动物实验表明,实验组兔尿道组织中TGF-β1免疫阳性面积分数[(4.21±1.32)%]小于模型组[(8.53±3.43)%](t=−4.24,P<0.001);实验组兔尿道组织中TNF-α免疫阳性面积分数[(5.14±2.72)%]小于模型组[(7.23±1.57)%](t=−3.37,P<0.05);实验组兔尿道组织中MMP-2水平[(10.65±2.24)%]高于模型组[(6.98±2.74)%](t=2.19,P<0.05);尿道周长[(12209±2743)μm]高于模型组[(10127±2237)μm](t=15.46,P<0.05)。结论成功设计了一台专用于兔尿道瘢痕的超声治疗仪,可用于超声对兔尿道瘢痕治疗的研究。

Objective To design a specialized ultrasound therapeutic device for rabbit urethral scars and to verify its applicability and effectiveness.Methods New Zealand male rabbits were used as the experimental objects,and the ultrasound therapeutic instrument was customized according to the structure and size of the rabbit penises.The ultrasound therapeutic instrument included the ultrasound pulse emission and control system,the final-stage amplifier,and the ultrasound probe.Firstly,the ultrasound probe was designed according to the size and structure of rabbit penises,and the parameters of the ultrasound probe were determined by COMSOL finite element simulation and actual testing of the sound field distribution.Secondly,the driving circuit of the ultrasound probe was designed according to the parameters of the elements.Then the ultrasound pulse emission and control system based on the field-programmable gate array(FPGA)and the serial screen were designed.Subsequently,the ultrasound therapeutic instrument was subjected to a performance test and a safety test.The ultrasound therapeutic instrument was constructed to include the ultrasound amplifier and the ultrasound probe.Finally,a rabbit urethra reconstruction model was constructed,and eight white rabbits were randomly divided into a model group and an experimental group.The rabbits in the experimental group received the ultrasound therapeutic instrument for treatment of the urethra immediately,with an ultrasound frequency of 2 MHz,a pulse interval of 10 ms,and an output sound intensity of 0.73 W/cm^(2).The treatment was performed twice a week(on Tuesday and Thursday),with 10 min of irradiation each time,lasting for four weeks.The rabbits in the model group did not receive any treatment.The area percentage of transforming growth factor-β1(TGF-β1),matrix metalloproteinase-2(MMP-2),and tumor necrosis factor-α(TNF-α)staining-positive areas in rabbit urethral tissues were quantitatively analyzed,and the urethral circumference was calculated using Image J software.Results Due to the addition of sound-absorbing materials,the sound pressure distribution in the treatment chamber was more uniform,and the average value of the standing wave ratio was 1.11,indicating that the structural design met the design requirements.In the overall performance test,the natural focal position of the three ultrasonic transducers was 10 mm,and the consistency of the sound field distribution meet the experimental requirements.The relationship between the peak sound pressure of each transducer and the power supply voltage was close to linear.The output sound intensity ranged from 0.35 to 0.74 W/cm 2,which met the experimental requirements.With the ultrasound output,the temperature of the test point increased slowly,and this experiment could increase the temperature of the tissue by up to 3.3℃,which would not lead to thermal damage to the tissue.Animal experiment results showed that the immunopositive area fraction of TGF-β1 in the urethral tissues of rabbits in the experimental group[(4.21±1.32)%]was smaller than that of the model group[(8.53±3.43)%](t=−4.24,P<0.001).The immunopositive area fraction of TNF-αin the urethral tissues of rabbits in the experimental group[(5.14±2.72)%]was smaller than that of the model group[(7.23±1.57)%](t=−3.37,P<0.05).The MMP-2 level in the urethral tissue of rabbits in the experimental group[(10.65±2.24)%]was higher than that of the model group[(6.98±2.74)%](t=2.19,P<0.05).The urethral circumference[(12209±2743)μm]was higher than that of the model group[(10127±2237)μm](t=15.46,P<0.05).Conclusions An ultrasound therapeutic instrument dedicated to rabbit urethral scars has been successfully designed and can be used for the study of ultrasound treatment of rabbit urethral scars.