经直肠超声探头位姿调整远心机构设计及实验研究

Study on the design and experiment of RCM for transrectal ultrasound probe position and posture adjustment

在临床手术中,最常用于诊断前列腺癌的方法是经直肠超声的前列腺活检手术。医生在手术期间需要全程手持超声探头进行反复调整,难以保证手术的效率、精度以及安全性。通过对经直肠超声引导下前列腺活检手术流程的分析,设计了一种7自由度被动式经直肠超声探头位姿调整远心机构。基于双平行四边形机构设计的姿态调整模块实现超声探头的定心功能,并对其进行运动学分析,基于SimMechanics对超声探头不同进给距离时的工作姿态和定心效果进行了仿真。研制了被动式经直肠超声探头位姿调整机构的物理样机,并进行了测量实验,实验结果可知超声探头不同进给距离时方位角远心点运动最大误差和俯仰角远心点运动最大误差分别为4和3.4 mm,均小于肛门处可承受的变形量6 mm。在不同方向下的随机误差相关性较弱,方位角和俯仰角的远心点运动误差置信区间均小于2.5 mm,最大相对定点误差和最大相对标准误差分别为14.73%和14.98%。仿真和实验结果以及测量误差的分析均验证了超声探头位姿调整机构定心性能的有效性和稳定性。

In clinical operation,transrectal ultrasound prostate biopsy is the most commonly used method for diagnosing prostate cancer.During operation,the doctor has to hold the ultrasound probe for repeated adjustments all the time,which is difficult to ensure the efficiency,accuracy and safety of the operation.In this paper,through analyzing the transrectal ultrasound guided prostate biopsy operation procedure,a 7-DOF passive transrectal ultrasound probe position and posture adjustment remote center mechanism is designed.The posture adjustment module designed based on double parallelogram mechanism realized the centering function of the ultrasound probe,and the kinematics analysis of the posture adjustment mechanism was carried out.The working posture and centering effect of the ultrasonic probe at different feeding distances was simulated based on SimMechanics.The physical prototype of the passive transrectal ultrasound probe position and posture adjustment mechanism was developed and measured in experiment.The experiment results show that the maximum errors of the azimuth angle remote center point motion and the pitch angle remote center point motion of the ultrasonic probe are 4 and 3.4 mm,respectively,which are less than the deformation of 6 mm that the anus can bear.The random error correlation in different directions is weak,the confidence interval width of the remote center point motion error of azimuth and pitch angles are less than 2.5 mm,and the maximum relative fixed point error and the maximum relative standard error are 14.73%and 14.98%,respectively.Therefore,the simulation results,experiment results and the measurement error analysis verify the effectiveness and stability of the centering performance of the proposed transrectal ultrasonic probe position and posture adjustment mechanism.