摘要目的 用热释光剂量计(TLD)和放射性免冲洗胶片测量调强放疗(IMRT)多叶光栅(MLC)野光子线束吸收剂量并验证二维剂量分布.方法 选择湖北省7家三级甲等医院的7台不同型号医用直线加速器,使用国际原子能机构(IAEA)提供的15 cm×15 cm×15 cm聚苯乙烯专用模体,TLD和放射性免冲洗胶片,在源皮距90 cm,照射深度10 cm,照射野5 cm×5 cm,6MVX射线,6 Gy吸收剂量照射条件下制定IMRT计划并实施照射,比较TLD和胶片吸收剂量测量值与放疗计划系统(TPS)预估剂量之间的偏差.同时,使用医院配备的30 cm×30 cm均质固体模体,在模体表面下5 cm处放置25 cm×25 cm放射性免冲洗胶片,并将IMRT计划中单个射野移植到模体中胶片层面上并实施照射,通过胶片剂量分析系统验证二维剂量分布.结果 所检医用直线加速器中,l号加速器TLD吸收剂量相对偏差和胶片吸收剂量相对偏差分别为-8.5％和-1.9％;7号加速器TLD吸收剂量相对偏差和胶片吸收剂量相对偏差分别为5.4％和0.5％;其余加速器TLD和胶片吸收剂量相对偏差均在±5％范围以内.所有加速器的二维剂量分布通过率均在90％以上.结论 TLD和胶片核查调强放疗剂量质量方法,操作简单,科学性强,TLD和胶片便于邮件方式寄送,该方法可运用于对放疗机构调强放疗剂量大范围的质量核查.

abstractsObjective To verify the absorbed dose and two-dimensional dosimetry delivered by MLC-shaped IMRT photon beams using thermoluminescent dosimeters (TLDs) and radiochromic films.Methods Different types of medical linear accelerators at 7 third-grade first-class hospitals in Hubei were selected for this audit study.Besides TLDs and films,a small polystyrene phantom measuring 15 cm × 15 cm × 15 cm,supplied by the International Atomic Energy Agency (IAEA),was also used.The TPS dose calculation were performed with 6 MV X-ray beam and by delivering 6 Gy dose to the TLDs or films at 10 cm depth for 5 cm × 5 cm field size at 90 cm SSD.After irradiation,comparations were conducted of dose derivations between TPS-calculated values and TLD-or film-measured values.The two-dimensional dosimetry audit was carried out by using 30 cm × 30 cm homogeneous solid phantoms in which a 25 cm × 25 cm film was located at 5 cm depth.A single-filed profile generated by TPS was delivered to the film,and the film was measured.And then,two-dimensional dose distribution was analyzed using the film analysis system.Results The results suggested that the relative deviations of TLD and film to TPS dose was-8.5％ and-1.9％ for accelerator 1,5.4％ and 0.5％ for accelerator 7,respectively,whereas those for other accelerators were within ± 5％.The passing rates for two-dimensional dose distribution at all accelerators were all higher than 90％.Conclusions TLD and film quality audit for IMRT can be applied for a wide range of application in view of its simplicity,reliability and postal convenience.