近距离放射治疗照射剂量准确性的研究

Study of the accuracy of dose delivery in brachytherapy

目的:研究我院近距离放疗照射剂量的准确性。方法:用显活度App穴Ci雪和空气比释动能率K觶穴cGy·m2·h-1雪两种方法校准192Ir源强。在水箱中心放置PTWM2331电离室,距电离室中心2cm处放置4根施源针,角度互为90°,运行预先设计的计划,测量剂量与处方剂量相对照。结果:用显活度校准源强最大误差-6.8%,平均误差4.38%,用空气比释动能率校准源强最大误差3.1%,平均误差2.4%。处方剂量与测量剂量的最大偏差5.11%,平均偏差3.87%。结论:用空气比释动能率K觶校准源强好于用显活度App校准源强。我院近距离治疗机的所有物理照射剂量的平均准确性符合ICRU24号报告提出的好于±5%的标准。

Purpose: To study the accuracy of dose delivery for brachytherapy in our Hospital. Method: Using apparent activity (Ci) in water method and Air Kerma Rate (cGy·m2·h-1) in-air method calibrated 192Ir source. The accuracy of the dose delivery was determined for HDR Nucletron Brachytherapy using a water box containing a PTW M23331 Ionization chamber in its center- 4 applicators were placed at 2 cm from the ionization chamber- equally spaced at 90° angles. Resules: In a comparison of sourcecalibration procedures for 192Ir HDR sources in water method found that the average deviations from the certificate's value was 4.38%- but the average deviation was 2.4% in-air method. The average deviation of the measured dose from the prescribed dose was 3.87%. Conclusions: This comparison showed that the accuracy of brachytherapy dose delivery has come up to the standard of ICRU 24# report.