虚拟仪器环境下小型智能化超声热疗系统设计

小型智能化医疗仪器是当今生物医学工程领域研究热点之一,而LabVIEW(LaboratoryVirtualInstrumentEngineeringWorkbench)由于其本身固有的优点为实现该功能提供了非常便捷的环境。文中介绍了在LabVIEW环境下小型超声热疗治癌仪工作原理及系统构成。温度传感器采用T型热电偶,放大电路由两级构成,内置冰点补偿,提高了温度性能。通过设计专门电路产生控制信号驱动数据采集卡内置的可编程计数器/定时器8254芯片并适当编程产生脉宽调制(Pulsewidthmodulation,PWM)方波作为超声能量控制信号。文中详细阐述了人体组织内实时闭环温度控制算法以及超声治疗头水温控制这两个系统核心子模块的软件设计。根据系统特殊要求,在癌变组织温度控制子程序中,改进了比例积分微分(PID)算法,实现了对靶区组织温度的严格控制。实验证明系统设计可靠,PID算法改进合理,满足热疗治疗要求。

System Design of Small Intellectualized Ultrasound Hyperthermia Instrument in the LabVIEW Environment

Small-scale intellectualized medical instrument has attracted great attention in the field of biomedical engineering, and LabVIEW (Laboratory Virtual Instrument Engineering Workbench) provides a convenient environment for this application due to its inherent advantages. The principle and system structure of the hyperthermia instrument are presented. Type T thermocouples are employed as thermotransducers, whose amplifier consists of two stages, providing built-in ice point compensation and thus improving work stability over temperature. Control signals produced by specially designed circuit drive the programmable counter/timer 8254 chip to generate PWM(Pulse width modulation)wave,which is used as ultrasound radiation energy control signal. Subroutine design topics such as inner-tissue real time feedback temperature control algorithm, water temperature control in the ultrasound applicator are also described. In the cancer tissue temperature control subroutine, the authors exert new improvments to PID(Proportional Integral Differential)algorithm according to the specific demands of the system and achieve strict temperature control to the target tissue region. The system design and PID algorithm improvement have experimentally proved to be reliable and excellent, meeting the requirements of the hyperthermia system.