辐射自显影胶片EBT2在单次曝光与多次曝光条件下的剂量学研究

Dosimetric study on autoradiography films EBT2 under single-exposure and multi-exposure

目的:研究辐射自显影胶片EBT2在全身放射治疗的剂量测量中单次辐照与多次累积辐照后的剂量学稳定性,从而判断是否可用单张胶片记录多分次治疗中的累积剂量。方法:对3张胶片分别给予200 cGy、400 cGy、800 cGy的辐照,分别在照射后10 h^96 h内进行多次测量,观察黑化时间对胶片剂量的影响;对3张胶片分别给予100 cGy、150 cGy、200 cGy的辐照,每天重复扫描5次共扫描4 d,并与第1次扫描结果相比较,分析重复扫描对胶片剂量的影响;将EBT2胶片分为2组,一组每日分别给予100 cGy、150 cGy、200 cGy的剂量照射,累计重复4 d;另一组分别一次性给予200 cGy、300 cGy、400 cGy、450 cGy、600 cGy、800 cGy,比较接受相同剂量不同照射方式下的胶片剂量。结果:辐照4 d后的胶片剂量相比于辐照24 h后的剂量要高2%~3%;累积照射4 d后的胶片剂量相比于单次接受同等剂量要低1.5%~2.5%。同时也发现扫描仪的灯光对胶片剂量并不产生明显影响。结论:辐射自显影胶片EBT2可以用于多次照射后累积剂量的测量。

Objective To evaluate the possibility of EBT2 films used for measuring accumulated dose of multiple fractionated radiotherapy by investigating the dosimetric stability of autoradiography films EBT2 undergoing single-exposure and multi- exposure during the general radiotherapy. Methods Three EBT2 films were irradiated by 200 cGy, 400 cGy, 800 cGy separately, and then multiple measurements were underwent in 10-96 hours after the exposure to observe the effect of darken time on the dosage of films. Another three EBT2 films were irradiated by 100 cGy, 150 cGy, 200 cGy separately, and the films were scanned 5 times a day and scanned for 4 days to analyze the effect of repeated scans on the dosage of films by comparing with the first scanning result. EBT2 films were divided into two groups. One group was irradiated by 100 cGy, 150 cGy, 200 cGy respectively per day for continuous 4 days, while the other group was irradiated by 200 cGy, 300 cGy, 400 cGy, 450 cGy, 600 cGy, 800 cGy in one time. And then the dosage of films which were delivered the same dose under different ways of exposure were compared. Results The dosage of films which were irradiated for continuous 4 days was 2%-3% higher than that of films irradiated for 24 hours, and 1.5%-2.5% lower than that of films which were delivered the same dose under singleexposure. Meanwhile, the light of the scanner had no obvious influence on the dosage of films. Conclusion Autoradiography films EBT2 can be used for measuring accumulated dose of multi-exposure.