How accurate is the planning of prostate brachytherapy in terms of number of seeds planned (purchased) and number actually used? My impression is that the planning is quite detailed regarding number and location of seeds. What events encountered during the placement would alter the number of seeds used versus the plan? I had 80 I-125 seeds ordered and either 56 or 58 used. Would this be considered normal? I suppose most patients would not know how many seeds were ordered but here we buy our own.