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目的:检测宫颈癌近距离放疗中曼彻斯特系统剂量分布,为质量控制及质量保证提供依据。方法:特制一双面模板,把插植针及软管放入槽内,夹入慢感光X光片,检测放射源的到位精度。把软管放入检测孔,电离室放在离源10cm处空气中测量放射源的活度。水箱中不放标本测量A点及其外1cm、2cm、3cm剂量,然后放入子宫及直管施源器,电离室放在A点外1cm、2cm、3cm处,执行2个后装治疗计划,测量各点的剂量,并与TPS推算值比较。结果:经检测,软管施源器的源到位误差约2～3mm,通过调整施源器的长度,源的到位精度在1mm内。源的顶端与插植针焊接点的距离约5mm。源活度实测与TPS推算值相差5.4%,各点的剂量学实测与TPS推算值关系复杂,水箱内无标本时实测偏差在6%内,放入子宫标本时测量误差最大为13.86%。A点外1cm、2cm、3cm剂量比值与理想平方反比定律比值偏差最大为8.01%。结论:TPS推算值与实测值偏差较小,说明目前临床使用的曼彻斯特系统结果可信。
Objective: To detect the distribution of Manchester system in brachytherapy of cervical cancer and to provide basis for quality control and quality assurance. Methods: A special double-sided template, the insertion of needles and hoses into the slot, sandwiched with slow-sensitive X-ray film to detect radioactive sources in place accuracy. The hose into the test hole, the ionization chamber placed in the air 10cm away from the source to measure the activity of radioactive sources. In the water tank, the specimen is measured at point A and the dose of 1 cm, 2 cm, and 3 cm outside, and then placed into the uterus and straight tube applicator. The ionization chamber is placed at point 1cm, 2cm and 3cm away from point A, The dose at each point was measured and compared with the estimated value of TPS. Results: After testing, the source error of the hose applicator was about 2 ~ 3mm. By adjusting the length of the applicator, the accuracy of the source was within 1mm. The distance between the tip of the source and the soldering point of the implant is about 5 mm. The difference between the measured and calculated TPS was 5.4%. The relationship between the measured dosimetry and the TPS was complicated. The measured error was 6% within the sample without any water sample and 13.86% when the sample was placed in the uterus. A point outside the 1cm, 2cm, 3cm dose ratio and ideal square inverse ratio of the law of the maximum deviation of 8.01%. Conclusion: The deviation of TPS estimated value from the measured value is small, indicating that the clinical results of the Manchester system are credible.