Melville G, Fan Liu Sau, Allen B J
Centre for Experimental Radiation Oncology, St. George Cancer Care Centre, Gray St. Kogarah, NSW, Australia.
Appl Radiat Isot. 2006 Sep;64(9):979-88. doi: 10.1016/j.apradiso.2006.05.002. Epub 2006 Jun 27.
Radium needles that were once implanted into tumours as a cancer treatment are now obsolete and constitute a radioactive waste problem, as their half-life is 1600 years. We are investigating the reduction of radium by transmutation on a small scale by bombarding Ra-226 with high-energy photons from a medical linear accelerator (linac) to produce Ra-225, which subsequently decays to Ac-225, which can be used as a generator to produce Bi-213 for use in 'targeted alpha therapy' for cancer. This paper examines the possibility of producing Ac-225 with a linac using an accurate theoretical model in which the bremsstrahlung photon spectrum at 18 MV linac electron energy is convoluted with the corresponding photonuclear cross sections of Ra-226. The total integrated yield can then be obtained and is compared with a computer simulation. This study shows that at 18 MV, the photonuclear reaction on Ra-226 can produce low activities of Ac-225 with a linac. However, a high power linac with high current, pulse length and frequency is needed to produce practical amounts of Ac-225 and a useful reduction of Ra-226.
曾经作为癌症治疗手段植入肿瘤的镭针如今已过时，并构成了放射性废物问题，因为其半衰期为1600年。我们正在研究通过用医用直线加速器（直线加速器）产生的高能光子轰击Ra-226来小规模地通过嬗变减少镭，以产生Ra-225，其随后衰变为Ac-225，可作为发生器来产生Bi-213用于癌症的“靶向α治疗”。本文使用精确的理论模型研究了用直线加速器产生Ac-225的可能性，在该模型中，18MV直线加速器电子能量下的轫致辐射光子能谱与Ra-226相应的光核截面进行卷积。然后可以获得总积分产额并与计算机模拟进行比较。这项研究表明，在18MV时，用直线加速器对Ra-226的光核反应可以产生低活度的Ac-225。然而，需要高功率、高电流、脉冲长度和频率的直线加速器来产生实际数量的Ac-225并有效减少Ra-226。
