Shih J L, Brugger R M
Nuclear Engineering Program, University of Missouri-Columbia 65211.
Med Phys. 1992 May-Jun;19(3):733-44. doi: 10.1118/1.596817.
The clinical results of treating brain tumors with boron neutron capture therapy are very encouraging. Researchers around the world are once again making efforts to develop this therapeutic modality. Gadolinium-157 is one of the nuclides that holds interesting properties of being a neutron capture therapy agent. It is estimated that tumor concentrations of up to 300 micrograms 157 Gd/g tumor can be achieved in brain tumors with some MRI contrast agents such as Gd-DTPA and Gd-DOTA, and up to 800 micrograms 157 Gd/g tumor can be established in bone tumors with Gd-EDTMP. Monte Carlo calculations indicate that with 250 ppm of 157Gd in tumor, neutron capture therapy can deliver 2000 cGy to a tumor of 2-cm diameter or larger with 5 x 10(12) n/cm2 of thermal neutron fluence at the tumor. Dose measurements with films and TLDs in phantoms verified these calculations. More extended Monte Carlo calculations demonstrate that neutron capture therapy with Gd possesses comparable dose distribution to B neutron capture therapy. With 5 x 10(12) n/cm2 thermal neutrons at the tumor, Auger electrons from the Gd produced an optical density enhancement on films that is similar to the effect caused by about 300 cGy of Gd prompt gamma dose and may further enhance the therapeutic effects.
用硼中子俘获疗法治疗脑肿瘤的临床结果非常令人鼓舞。世界各地的研究人员再次努力开发这种治疗方式。钆-157是具有作为中子俘获治疗剂有趣特性的核素之一。据估计，使用一些磁共振成像造影剂如钆-二乙三胺五乙酸（Gd-DTPA）和钆-四氮杂环十二烷四乙酸（Gd-DOTA），脑肿瘤中钆-157的肿瘤浓度可达300微克/克肿瘤，而使用钆-乙二胺四甲撑膦酸（Gd-EDTMP），骨肿瘤中钆-157的浓度可达800微克/克肿瘤。蒙特卡罗计算表明，肿瘤中钆-157含量为250 ppm时，中子俘获疗法可在肿瘤处热中子注量为5×10¹² n/cm²的情况下，向直径2厘米或更大的肿瘤输送2000 cGy的剂量。在体模中用胶片和热释光剂量仪进行的剂量测量验证了这些计算结果。更广泛的蒙特卡罗计算表明，钆中子俘获疗法的剂量分布与硼中子俘获疗法相当。在肿瘤处有5×10¹² n/cm²热中子的情况下，钆产生的俄歇电子在胶片上产生的光密度增强类似于约300 cGy的钆瞬发γ剂量所产生的效果，可能会进一步增强治疗效果。
