1 research outputs found
Single dose irradiation response of pig skin: a comparison of brachytherapy using a single, high dose rate iridium-192 stepping source with 200 kV X-rays
An experimental brachytherapy model has been developed to study acute and
late normal tissue reactions as a tool to examine the effects of
clinically relevant multifractionation schedules. Pig skin was used as a
model since its morphology, structure, cell kinetics and radiation-induced
responses are similar to human skin. Brachytherapy was performed using a
microSelectron high dose rate (HDR) afterloading machine with a single
stepping source and a custom-made template. In this study the acute
epidermal reactions of erythema and moist desquamation and the late dermal
reactions of dusky mauve erythema and necrosis were evaluated after single
doses of irradiation over a follow-up period of 16 weeks. The major aims
of this work were: (a) to compare the effects of iridium-192 (192Ir)
irradiation with effects after X-irradiation; (b) to compare the skin
reactions in Yorkshire and Large White pigs; and (c) to standardize the
methodology. For 192Ir irradiation with 100% isodose at the skin surface,
the 95% isodose was estimated at the basal membrane, while the 80% isodose
covered the dermal fat layers. After HDR 192Ir irradiation of Yorkshire
pig skin the ED50 values (95% isodose) for moderate/severe erythema and
moist desquamation were 24.8 Gy and 31.9 Gy, respectively. The associated
mean latent period (+/- SD) was 39 +/- 7 days for both skin reactions.
Late skin responses of dusky mauve erythema and dermal necrosis were
characterized by ED50 values (80% isodose) of 16.3 Gy and 19.5 Gy, with
latent periods of 58 +/- 7 days and 76 +/- 12 days, respectively. After
X-irradiation, the incidence of the various skin reactions and their
latent periods were similar. Acute and late reactions were well separated
in time. The occurrence of skin reactions and the incidence of effects
were comparable in Yorkshire and Large White pigs for both X-irradiation
and HDR 192Ir brachytherapy. This pig skin model is feasible for future
studies on clinically relevant multifractionation schedules in a
brachytherapy setting