The utilization of I-125 seeds as a substitute for Ir-192 seeds in temporary interstitial implants: an overview and a description of the William Beaumont Hospital technique.

In August of 1986, the Department of Radiation Oncology at William Beaumont Hospital (WBH) initiated the routine use of high activity I-125 seeds as a substitute for Ir-192 seeds in temporary implants where the afterloading plastic tube technique was used. Through March 6, 1987, 42 temporary I-125 implants were performed as a boost for curative therapy (38 breasts, 2 sarcomas, 2 tongues). Thus far, we have observed no differences in acute toxicity. Sources ranging from 2 to 5 mCi were utilized. The advantages of I-125 are as follows: (a) Easy to shield; (b) Radiation safety; (c) Decreased exposure to sensitive organs in close proximity to the implanted site; (d) Dosimetric advantages both intrinsic and extrinsic; and (e) Any private room can be used for these patients allowing a central brachytherapy ward to be established. While the advantages were obvious, we anticipated potential disadvantages and shortcomings and these will be discussed in detail. Furthermore because of significant differences in tube and ribbon construction, the I-125 afterloading plastic tube technique has important differences from that technique used with Ir-192. These modifications must be fully understood to maintain the integrity of the I-125 seed-ribbon afterloading tube assembly. A detailed description of the technique will be emphasized.