All animals were anesthetized by an intraperitoneal injection of the association of ketamine hydrochloride (Ketamin, Cristalia, Brazil) 100 mg/kg and xylazine hydrochloride (Rompun, Bayer, Brazil), 5 mg/kg. They were placed in ventral decubitus and an area of 10 × 6 cm in the back of the animal was trichotomized.

Two strontium plaques were applied per animal (dorsal region to reduce sample size). The areas of radiation were at least 3 cm apart to avoid crossover effect.

Radiation was delivered with two strontium-90 (90Sr) dermatological plaques that emitted beta radiation (model SIQ21, with reference dose rate = 0.051 Gy/s and Model SIQ18 with reference dose rate = 0.048 Gy/s, Amersham International plc). Two areas of 2 × 2 and 2 × 1 cm in the dorsum of each animal were exposed to a single dose of 20 Gy810.

After the radiotherapy session, the animals were kept in vivarium for 15 days until the radiodermatitis lesions onset.

After this period, they were divided into two groups:

Control group: n = 5, no further treatment;

Intervention group LED: n = 5, exposure to LED (wavelength 660 nm), one session lasting 10 min, on alternate days, for the following 21 days.