摘要目的 建立计算放射性粒子植入治疗生物有效剂量(BED)和2 Gy分割生物等效剂量(EQD2)的模型.方法 引入根据L-Q模型建立的外照射BED计算公式和持续低剂量照射BED计算公式.结合BED公式,根据EQD2的定义,建立持续低剂量率照射(放射性粒子植入治疗)的EQD2计算公式.总结常见组织的α/β值和见于文献报道正常组织的Tr1/2值,利用实际值,进一步简化EDQ2计算公式,提出早反应组织和晚反应组织的EDQ2计算经验公式,并命名为王-彭经验公式.对于早反应组织,EQD2≈10D/12(王-彭公式1);对于晚反应组织,EQD2≈D/2(王-彭公式2).进一步举例说明本文所建立公式在临床上的应用,包括原发性肺癌、食管癌锁骨上淋巴结转移和宫颈癌腹膜后淋巴结转移.结果 根据王-彭经验公式,肿瘤临近的晚反应组织的EQD2仅约为肿瘤组织受量的一半,故而放射性粒子植入治疗“天然地”从生物等效剂量上对晚反应的组织进行了保护.通过实际计算,发现早反应组织的经验公式较为精确,而晚反应组织的经验公式精确度略差,只能做粗略估计.结论 本研究引入的BED计算公式和据此建立的一系列EQD2计算公式以及王-彭经验公式,在理论上可行,可用于放射性粒子植入治疗的物理剂量与外照射剂量之间的换算和叠加.但是使用公式时应谨慎,注意预设条件,慎重解读计算得出的结果.

abstractsObjective To establish a model for the calculation of biologically effective dose (BED) and EQD2 (Equivalent dose in 2 Gy fractions) in radioactive seed implantation brachytherapy.Methods The BED formula for EBRT(external beam radiotherapy) and for continuous low dose-rate irradiation established under the L-Q model were introduced.The EDQ2 formula for the continuous low dose-rate irradiation (radioactive seed implantation) was established according to the definition of EQD2 and the formula of BED.The α/β values of common tissues and the Tr 1/2 values reported in the literature were summarized.The EDQ2 formula were further simplified by using the actual values.The empirical formula of EDQ2 for early reaction tissues and late reaction tissues were proposed,named as Wang-Peng empirical formula.EDQ2≈ (10/12) D (Wang-Peng Formula 1) was fit for early response tissue,and EDQ2≈ D/2 (Wang-Peng Formula 2) for late reaction tissues.Further examples on the clinical applications of the proposed formula were given,including primary lung cancer,supraclavicular lymph node metastasis of esophageal cancer and celic lymph node metastasis of cervical carcinoma.Results According to the Wang-Peng empirical formula,the EDQ2 of the late reaction tissue adjacent to the tumor was only about half that of the tumor tissue,so the radioactive seed implantation brachytherapy "naturally" protected the late reaction tissue by the biological equivalent dose.The actual calculation,showed that the empirical formula of early reaction tissue was more accurate,but the empirical formula of late reaction orgtissue was less inaccurate and could only be roughly estimated.Conclusions The BED calculation formula introduced here and the set of EQD2 calculation formula and Wang-Peng empirical formula established here were theoretically feasible and could be used for the conversion and superposition between the physical dose of radioactive seed implantation brachytherapy and the external irradiation dose.But it should be careful to apply the formula,pay attention to the default conditions,and carefully interpret the calculated results.