大射野、大深度照射条件下组织-空气比的测量

Measurement and calculation of tissue air ratios of cobalt 60 gamma radiation in large field and depth.

目的组织－空气比是用于放射治疗和诊断剂量学及事故剂量估算最重要的物理量之一，而目前国内外尚没有大射野、大深度照射条件下组织－空气比数据文献报道。方法本文以６０Ｃｏγ放射源，采用固定探测器，改变源皮距的实验方法，测量了深度至７０．０ｃｍ，射野至５０．０ｃｍ×５０．０ｃｍ的组织－空气比数值。结果实验测量结果同文献现有数据比较，相对误差小于±５％。结论测量大射野、大深度照射条件下组织－空气比数据对于放射事故外照射人体剂量估算及放射诊断、治疗剂量学具有重要的意义。

Objective\ Tissue air ratio(TAR) is the one of useful concepts and methods in radiation dosimetry.There are no available TAR data for large field and depth irradiation and more research is needed to investigate the properties of TAR and other relative quantities under special irradiation. Methods\ Data of TAR for depth up to 70.0cm and rectangular field size up to 50.0cm×50.0cm have been obtained for 60 Coγ rays. Results\ For depth less than 30.0cm and field size less than 50.0cm×50.cm, the relative errors between the data by the experiment and by reference are less than 5 percent. Conclusions\ It is very important to measure TAR under the condition of irradiation in large depth and field sizes for the measurment and calculation of dose distribution in human body after a radiological accident.