摘要
(上標 252)鉲是唯一放射中子的人造放射性同位元素，在臨床上用作短距離放療。(上標 252)鉲的半衰期是265年，3％的衰變為自然裂變，發出γ和中子射線，其平均能量為2.35 MeV，n/γ射線劑量比為840/740 cGy, OER值為l.4~l.9，隨劑量率加大而升高。(上標 252)鉲的RSE值為3.5~7.5，劑量率低，則RBE高。由於(上標 252)鉲發出中子和加馬射線，臨床使用時，對工作人員的輻射屏蔽便顯得特別重要，過去二年末文獻的臨床經驗顯示， (上標 252)鉲可用作子宮頸癌腔內治療，通常合併體外X線全骨盆腔照射或手術切除，局部腫瘤控制率可達77至94％。2 紹鋒亦可用於舌癌的反向運動挿植治療，對早期舌癌的復發率為6%, 晚期舌癌復發率約三分之一，(上標 252)鉲亦可用於乳癌、頭頸癌或直腸癌的挿植治療，短期腫瘤消退率達75至100%，復發率14至25%。
並列摘要
(superscript 525) Californium is the only one man-made radiosotope emitted neutrons which can be used clinically for brachytherapy. The halflife of (superscript 525)Cf is 2.65 years, 3% of decay are natural nuclear fission emitting gamma and neutron radiations, the mean energy of radiation is 2.35 MeV, n/γ dose ratio is 840/740 cGy. OER value is 1.4~4.9, it is higher when the dose rate is higher. The RBE value of 252Cf vary between 3.5 and 7.5, it is higher when dose rate is lower. Since 252Cf emits both gamma and neutron radiations, radiation protection for the personnel become very important. Literature reviewed indicated that intracavitary brachytherapy with 252Cf combined with external beam whole pelvis irradiation or plus surgery provided 77 to 94% local tumor control rate. Implantation of 255Cf in early as well advanced tongue cancer showed 6% and 33% recurrent rates respectively. 252Cf implantation could be used for cancer of breast, head and neck and rectum etc, the immediate tumor regression rate could be as high as 75 to 100%, the tumor recurrent rate varied between 14 to 25%.
延伸閱讀
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