In permanent brachytherapy, tiny radioactive "seeds" are implanted directly into a tumor, such as in the treatment of localized prostate cancer. Iodine-125, which emits low-energy photon radiation, is commonly selected for these implants instead of a high-energy gamma-emitting isotope.
Explain one advantage of using an isotope that emits low-energy photons rather than high-energy gamma radiation for permanent implants.
