Radiation exposure rates near brachytherapy patients containing 137Cs sources.

For 30 brachytherapy patients, whose lateral pelvic diameters, 2r, ranged from 28 to 47 cm, and who contained activities Ac of 137Cs expressed in equivalent milligrams of 226Ra, the normalized exposure rates, X(r)/Ac, in mR h-1 (mg Ra eq)-1 at 1 m lateral from the midline of the pelvis, can be expressed by X(r)/Ac = (1.3 +/- 0.5)e-(0.07 +/- 0.02)r. Patient and applicator effects that contribute to the large uncertainties in the model coefficients are identified.