ラドンシード Radon seed
It had been developed by G. Failla in 1924 that radon seed was a perm anent implant source for brachytherapy sealed 222Rn gas in thin gold tube. In Japan, the first radon plant was installed at Cancer Institute Hospital, Tokyo, by H. Yamagiwa and M. Miwa in 1935. This plant broken off the war was resumed in 1947, and radon seeds of 231,279 were supplied from Cancer Institute Hospital between 1947 and 1975.<BR>The gamma ray output of radon seed in the supply was equivalent to 1 mg radium with Platinum wall thickness of 0.5 mm. But, the dose rate within 5 mm from source measured with TLD was 45% greater than that calculated only gamma ray because of leakage of beta rays.<BR>Technicians in the radon seed production received very much radiation exposure exceed dose limit. However, they do not have on radiation injury at the present time.
放射線医学物理 18(2), 146-152, 1998-06-30
Japan Society of Medical Physics