EPR在体测量专用调制磁场驱动装置

利用电子顺磁共振（electron paramagnetic resonance，EPR）在体测量人牙齿可以实现无损伤地快速评估人体辐射剂量，具有实际应用价值.本文针对EPR在体测量牙齿剂量的应用特点，研制了专用调制磁场驱动装置，包括功率放大器、调制磁场激励线圈、调制频率设定模块、感应型调制幅度显示模块等.功率放大器采用脉冲功率放大方式取代传统的线性放大方式，用多N-MOSFET管H桥电路，功率容量大、效率高、结构简单，且调制频率设定自如.实验结果表明：（1）此装置可在大于9 cm磁极间距的中心样品位置产生调制幅度为0~0.9 mT的调制磁场，调制频率为10~100 kHz；（2）用该装置与EPR在体测量谱仪配合使用，可以明显观测到1，1-二苯基-2-三硝基苯肼（1，1-diphenyl-2-picrylhydrazyl，DPPH）样品谱线调制增宽过程以及辐射诱发的整体牙齿中的自由基信号，验证了该装置的高调制效率和实用性.

An EPR Modulation Magnetic Field Driving Device for in Vivo Tooth Dosimetry

In vivo electron paramagnetic resonance (EPR) tooth dosimetry can be used to estimate the absorbed radiation dose quickly and noninvasively. In this study, a magnet modulation driving device was developed for in vivo EPR tooth dosimetry. The device included a driving amplifier, a couple of coil sets generating modulation magnet field, a modulation frequency setting unit and a display unit. The driving amplifier used a switching circuit based on multi N-MOSFET H-bridge, instead of the traditional linearly analogue circuit. The amplifier had the characters of higher power capacity, high efficiency, simple structure and high flexibility for frequency setting. Experimental results showed that (1) the device could generate modulation magnet field, 0~0.9 mT in amplitude and 10~100 kHz in frequency, in the center of the two magnet poles separated more than 9 cm apart; (2) line broadening process feature of 1,1-diphenyl-2-picrylhydrazyl (DPPH) was observed with increasing modulation amplitude and radiation induced free radical signals in intact tooth. The preliminary results demonstrated that the device developed for in vivo EPR tooth dosimetry had high-efficiency and practicability.