Permanent implants using Au-198, Pd-103 and I-125 : radiobiological considerations based on the linear quadratic model

摘要: Based on the linear-quadratic model, we perform calculations to compare possible radiobiologic results achieved with permanent implants using Au-198, Pd-103, and I-125. We examine influence of radiobiophysical parameters (i.e. alpha, beta, SLD repair kinetics, tumor doubling time (Tp), growth delay, prescribed dose) calculated indices or endpoints. The endpoints include effective treatment (Teff) (beyond which additional dose delivered is wasted), biologically (BED), cell surviving fractions. Within range reported values various parameters, Tp most significant in affecting Teff, BED, degree inactivation. effect Teff BED larger for isotopes longer half-lives, rate regrowth more important. For 5 30 days, are 14 21 days 58 102 120 275 this Tp, wasted doses less than 5% 15 3% reference prescription 60, 120, 160 Gy I-125, respectively, associated cell-kill lowest whereas Pd-103 I-125 fast-growth (Tp 10 days) slow-growth greater tumors, respectively.