适用于重离子治癌剂量监测的电流-频率转换电路设计

发布时间：2018-10-08 18:55

【摘要】：重离子治癌以其具有能量损失集中于射程末端的物理学特性以及高的相对生物学效应的优点,被视为最理想的放射治癌方法。中国科学院近代物理研究所基于兰州重离子研究装置(HIRFL)自主设计重离子治癌装置,已完成浅层和深层治癌临床试验,成为世界上第四个进行了重离子临床试验的国家。重离子临床照射治疗时,为使肿瘤受到均匀且足够剂量的照射,而周围组织尽可能少受损伤,保障医疗的安全性与可靠性,需要对辐照剂量进行实时测量与监控。深层治癌中束流强度监测系统的剂量监测探测器采用积分电离室,输出的电流信号正比于束流强度。深层治癌中照射束流的强度为0~109pps,电离室输出电流信号峰值小于1μA,属于小信号。为了测量该电流信号,本论文设计了一种新的电流频率转换电路。在电路设计过程中,分析讨论了各种弱电流测量方案的优点与不足之处,最终选择了可变阈值电流积分泄放式电流频率转换的方案。本论文对所设计电路的硬件及逻辑部分进行详细介绍,并给出论文完成过程中设计的两版电路调试及测试结果。本论文设计了两种精度的电流频率转换电路:10pC/pulse和0.5pC/pulse。10pC/pulse电路能够完成双极性电流的测量,在输入电流极性改变时切换简单。负电流测量范围为0.1nA~70μA,整个范围内线性度好于0.46434%;正电流测量范围为1nA~60μA,整个范围内线性度好于0.34288%。0.5pC/pulse电路测量范围为0.01nA~500nA,整个范围内线性度好于0.04168%,完全满足在实际应用中的要求。论文最终对电流频率转换电路的结构功能进行总结,并对下一步工作的方向和电路改进进行展望。
[Abstract]:Heavy ion therapy is regarded as the most ideal method for cancer treatment because of its physical characteristics of energy loss at the end of range and its high relative biological effect. The Institute of Modern Physics of the Chinese Academy of Sciences has independently designed a heavy ion cancer treatment device based on Lanzhou heavy Ion Research Facility (HIRFL). It has completed the shallow and deep cancer treatment clinical trials and has become the fourth country in the world to conduct heavy ion clinical trials. In order to make the tumor receive a uniform and sufficient dose of irradiation, and the surrounding tissue be damaged as little as possible, to ensure the safety and reliability of medical treatment, it is necessary to measure and monitor the radiation dose in real time. In the deep cancer treatment, the dose detector of the beam intensity monitoring system adopts an integrated ionization chamber, and the output current signal is proportional to the beam intensity. In deep cancer treatment, the intensity of irradiating beam is 0 ~ 109pps, and the peak output current signal of ionization chamber is less than 1 渭 A, which is a small signal. In order to measure the current signal, a new current frequency conversion circuit is designed in this paper. In the process of circuit design, the advantages and disadvantages of various weak current measurement schemes are analyzed and discussed. Finally, the variable threshold current integral discharge current frequency conversion scheme is selected. In this paper, the hardware and logic of the designed circuit are introduced in detail, and the debugging and testing results of the two sets of circuits designed during the completion of the thesis are given. In this paper, two kinds of precision current-frequency conversion circuits: 10 PC / pulse and 0.5pC/pulse.10pC/pulse circuits are designed to measure the bipolar current, which is simple to switch when the polarity of input current changes. The measurement range of negative current is 0.1nA~70 渭 A, the linearity of the whole range is better than that of 0.46434, the range of positive current measurement is 1nA~60 渭 A, the linearity of the whole range is better than that of 0.34288%.0.5pC/pulse circuit, and the linearity of the whole range is better than 0.04168, which fully meets the requirements of practical application. Finally, the structure and function of current-frequency conversion circuit are summarized, and the future work and circuit improvement are prospected.
【学位授予单位】：中国科学院大学(中国科学院近代物理研究所)
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM46;O571.6

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