The relative biological effectiveness of I-125 and Pd-103.
OBJECTIVE
To determine the relative biological effectiveness (RBE) of I-125 and Pd-103 relative to Co-60.


METHODS
A cell line REC:ras, derived from rat embryo cells, was used. Cells in exponential or plateau phase were irradiated at dose rates of about 0.07 Gy/h and 0.14 Gy/h. To circumvent the interface effect, cells were grown and irradiated on membranes made of cellulose acetate, which has an effective Z of 7.5. I-125 and Pd-103 seeds were placed in a custom designed template that yielded a homogeneous dose distribution in the plane of the cell culture. The dose rates of irradiation were measured by calibrated thermoluminescence dosimetry (TLD) chips.


CONCLUSIONS
Our measurements yielded an RBE of about 1.4 for I-125 at dose rates of about 0.07 Gy/h, and an RBE of about 1.9 for Pd-103 at dose rates of about 0.07 Gy/h and 0.14 Gy/h. The RBE of I-125 is similar to those measured by other investigators, the RBE for Pd-103 is being reported for the first time.
Ling
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CC
Laboratory of Radiation Biophysics, Memorial Sloan Kettering Cancer Center, New York, NY 10021, USA.
Li
W X
WX
Anderson
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LL
D000818:Animals; D002460:Cell Line; D002470:Cell Survival / Q000528:radiation effects; D004307:Dose-Response Relationship, Radiation; D007457:Iodine Radioisotopes / Q000627:therapeutic use*; D010165:Palladium / Q000627:therapeutic use*; D011868:Radioisotopes / Q000627:therapeutic use*; D011879:Radiotherapy Dosage; D051381:Rats
D007457:Iodine Radioisotopes; D011868:Radioisotopes; D010165:Palladium