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目的:测量换源后钴机的灯光野与射野的符合性和射野半影大小,评价其能否适合运用于临床治疗。方法:选择5个射野面积分别为:3cm×3cm,5cm×5cm,10cm×10cm,15cm×15cm,20cm×20cm;在深度为82、85、90 cm三个深度放置剂量验证胶片,钴机照射每张胶片时间为1 min;分析每张剂量验证胶片半影(P80%~20%)大小以及灯光野与射野的符合性。结果:半影大小随照射野面积和深度增大而增大,最小为6 mm,最大为16.8 mm;灯光野与射野的符合性在y轴上较好,在x轴方向,灯光野相对于射野向x负方向偏移,最大为1.2 mm。结论:该钴机改装后,半影大小以及灯光野与射野的符合性达到GBZT161-2004医用γ射束远距治疗防护与安全标准,可用于临床治疗。
OBJECTIVE: To measure the conformity of the light field of the cobalt machine and the field and the size of the penumbral area after the source replacement, and evaluate whether it is suitable for clinical treatment. Methods: Five fields were selected as 3cm × 3cm, 5cm × 5cm, 10cm × 10cm, 15cm × 15cm and 20cm × 20cm, respectively. At the depth of 82, 85 and 90 cm, The duration of exposure to each film was 1 min; the size of the penumbra (P80% to 20%) for each dose was verified and the conformity of the light field to the field was analyzed. Results: The size of penumbra increased with the increase of irradiation area and depth, with a minimum of 6 mm and a maximum of 16.8 mm. The compliance of the light field with the field was better on the y-axis and the relative light field in the x-axis In the radio field to x negative direction of the shift, a maximum of 1.2 mm. CONCLUSION: After the cobalt machine is modified, the penumbra size and compliance of the light field with the radiation field reach GBZT161-2004 medical γ-ray teletherapy protection and safety standards, which can be used for clinical treatment.