Radioactivity characterization of .sup.125I brachytherapy seeds used in prostate cancer treatment

A procedure for characterizing the activity amount of .sup.125I seed was developed in order to establish a secondary standard activity measurement system based on an IG11 ionization chamber. Initially the ion current generated by the seed in the ionization chamber is measured and then its activity determined in a destructive analysis. The analysis consists in complete dissolution of the seeds to obtain a homogeneous solution to enable the primary measurements based in the coincidence sum-peak measurements. The measured current and activity allows determining the calibration factor, in pA MBq.sup.-1, for seed geometry. A detailed description of the procedure implemented for the seed dissolution is described.