高能电子束治疗中挡铅的质量保证

Quality assurance of adding blocks in high-energy eletron beam therapy

目的探索高能电子束挡铅的最佳厚度，以保护病人的正常组织，方法源皮距定为100cm，测量各档电子束在不同厚度挡铅下，水箱中最大剂量深度处的吸收剂量。结果吸收剂量随挡铅厚度增加近似成指数衰减，当挡铅厚度达到某一程度后，挡铅下的吸收剂量并不随挡铅厚度的增加而明显减少。结论为了在病人治疗中为保护其正常组织，随着能量的升高，挡铅也要求加厚，6MeV、9MeV宜用6mm厚的铅橡皮，12MeV宜用12nm厚的铅橡皮，15MeV宜用30mm厚的铅橡皮，18MeV以上的电子束则不能用铅橡皮，而要特制模块来挡铅。

Objective To assess the best thickness of adding blocks in high -- energy electron beam therapy,and protect patients nomal tissue. Methds The SSD was 100cm, absorPtion doses of water at Dmax were measured ineach energy electron beam with different thick blocks. Results Absorption doses were declined exponentially and ap- proximatly along with the increase of blocks thickness. After the tihckness got to special degree, declined no longerre- markable. Conclusion To protect normal organizations in electron beam therapy, blocks thickness should be added withenergy increasing. For 6Mev and 9Mev electron beam, 6mm thick rubber lead should be used, 12mm thick for 12Mevand 30mm thick for 15Mev, special block mold was needed when energy of electron beam was beyond 18Mev.[