Investigation of 125I as an isotopic source for mammography.

An isotopic radiation source 125I was investigated for use in soft tissue radiaography, with particular attention to possible use in mammography for mass screening. Film sensitivities, exposure rates, absorbed doeses, contrast and resolution were determined, and compared to conventional x-ray units. It was found that contrast and resolution were comparable to 30 kVp x-rays (W anode) but that surface absorbed dose was reduced by a factor of two with 125I. These results experimentally verified the advantage to be obtained from monoenergetic radiations, which had been predicted from theoretical considerations by others. Duration of exposure was estimated to be between 4 and 12 sec with a 40 Ci source. The 60-day half life of 125I may necessitate its use in conjunction with an image intensification system or electron radiographic techniques, in order to preclude source replacement at inconveniently short intervals.