title: Samarium-145: a new brachytherapy source.
abstract: A new radiation source has been produced for brachytherapy, with radiation energies slightly above those of 125I, and a T1/2 of 340 d. This source, 145Sm, is produced by neutron irradiation of 144Sm (96.5% enriched). Decay is by electron capture with 140 K x-rays per 100 disintegrations in the energy region between 38-45 keV, plus 13 gamma-rays at 61 keV. These sources are encapsulated in Ti tubes, approximately 0.8 mm X 4.5 mm, and have been developed for temporary implantation in brain and ocular tumours. The 38-61 keV photons should make such sources easy to shield, while providing a dose distribution from source arrays somewhat more homogeneous than that from 125I. In addition, the 340 d half life of 145Sm permits its use for times significantly longer than that of 60 d 125I. While the 145Sm sources have been designed primarily for implantation in a brain tumour, they should be useful for almost any conventional brachytherapy application.
mesh_terms: D001918:Brachytherapy; D001932:Brain Neoplasms / Q000532:radiotherapy*; D005134:Eye Neoplasms / Q000532:radiotherapy*; D006801:Humans; D008962:Models, Theoretical; D011868:Radioisotopes / Q000627:therapeutic use*; D011879:Radiotherapy Dosage; D012493:Samarium / Q000627:therapeutic use*
chemical_list: D011868:Radioisotopes; D012493:Samarium