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Encapsulated iodine-125 in radiation oncology. I. Study of the Relative Biological Effectiveness (RBE) using low dose rate irradiation of mammalian cell cultures

Journal Article · · Am. J. Clin. Oncol.; (United States)
; ;
The use of encapsulated iodine-125 seeds has increased considerably since 1965, due largely to their physical characteristics. The 28 keV x-ray emission offers improved radiation protection and rapid fall-off of dose outside the treatment volume. The Relative Biological Effectiveness (RBE) of the low energy I-125 x-rays has not been adequately assessed. The limited studies have found a wide range of values, but most are between 1.2-1.5 relative to hard x-rays. C3H/10T1/2 mouse embryo cells were used in contact inhibited plateau phase to assess the RBE of I-125 seed x-rays relative to Cs-137 gamma rays (660 keV) using low dose rate continuous irradiation. Replicate experiments found the RBE to be 1.2. This did not vary with dose rate over the range of 10-76 cGy/hour. Calculations made from cell survival data suggest that, in the case of permanent I-125 implants, where the dose is administered over a considerable period of time, the resultant surviving fraction of tumor cells is dictated largely by the length of the cell cycle. It is suggested that, for this reason, permanent I-125 implants may be less suitable for rapidly growing tumors, such as glioblastomas, than temporary I-125 implants, which are calculated to be virtually independent of the cell cycle duration.
Research Organization:
Columbia Univ., NY
OSTI ID:
5663378
Journal Information:
Am. J. Clin. Oncol.; (United States), Journal Name: Am. J. Clin. Oncol.; (United States) Vol. 7:6; ISSN AJCOD
Country of Publication:
United States
Language:
English

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Related Subjects

560152* -- Radiation Effects on Animals-- Animals
63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
ALKALI METAL ISOTOPES
ANIMAL CELLS
ANIMALS
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
CELL CULTURES
CELL CYCLE
CELL KILLING
CESIUM 137
CESIUM ISOTOPES
COMPARATIVE EVALUATIONS
DAYS LIVING RADIOISOTOPES
DOSE RATES
ELECTROMAGNETIC RADIATION
ELECTRON CAPTURE RADIOISOTOPES
EMBRYONIC CELLS
IMPLANTS
INTERMEDIATE MASS NUCLEI
IODINE 125
IODINE ISOTOPES
IONIZING RADIATIONS
IRRADIATION
ISOTOPES
LOW DOSE IRRADIATION
MAMMALS
MICE
NUCLEI
ODD-EVEN NUCLEI
RADIATION SOURCE IMPLANTS
RADIATION SOURCES
RADIATIONS
RADIOISOTOPES
RBE
RODENTS
VERTEBRATES
X RADIATION
YEARS LIVING RADIOISOTOPES