亚毫米级平板电离室辐射剂量特性初步研究

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中图分类号：TB9;TL811.1 文献标志码：A文章编号：1674-5124（2025）09-0141-07

Abstract： When measuring the dose in FLASH radiation fields， existing ionization chambers suffer from significant ion recombination effects，making it difficult to meet measurement requirements.To address this issue，this study developed anew ionization chamber to improve charge collection efciencyand investigated its dosimetric characteristics to enable accurate dose measurement in FLASH radiation fields.Based on the Gotz one-dimensionaltransport modeland finiteelement analysis method，the key parameters oftheionization chamber were determined.A prototype paralel-plate ionization chamber with an electrode spacing of 250μm and a sensitive volume of 19.6mm3 was developed，and its radiation dose characteristics were preliminarily studied.The results show that the plateau region of the ionization chamber's plateau curve （measured in a 60Co （204号 γ continuous radiation field） is narrow.The leakage current of the chamber is within ±5 fA in the absence of irradiation.It exhibits good dose linearity in the dose rate range of 1.88Gy/h to 75.33Gy/h ，with arepeatability within 0.5% .Undera dose rate of 7.35mGy/s ，the charge collection efficiency of the prototype chamber， calculated using the two-voltage method，is greater than 99% .Dose linearity measurements in the FLASH radiation field show that within a cumulative dose range of1.59 Gy to 49.69 Gy （single pulse dose of 1.59 Gy/pulse），theresponseof the ionization chamber demonstrates good linearity with the dosemeasured by film. The preliminary performance study indicates that the parallel-plate ionization chamber prototype possesses favorable dosimetric characteristics，laying a foundation for further research on radiation dose measurement under ultra-high dose rate conditions.

Keywords：FLASH radiation field;ionrecombination effect;dose measurement; ionization chamber

0 引言

近年来，基于FLASH效应的超高剂量率（ultra-highdoserate，UHDR）放射治疗作为一种新型治疗技术已经在动物和人体上开展了实验研究，并取得较好的临床效果[1-6]。（剩余9919字）