How much radiation dose to the skin is necessary for the production of erythema?
Erythema may appear within a few hours after acute exposure to radiation with a skin dose of about 2 to 3 gray (Gy) for radiation energies encountered in X ray machines used for interventional procedures, whereas 6 to 8 Gy with 200 kV radiation used in radiation therapy are required for erythema to occur. Radiation of higher energies requires larger doses to produce the same degree of erythema since in these cases the maximum dose is received below the skin. Since erythema falls into the category of effects called deterministic effects that have a threshold, theskin dose of 2 Gy is considered the threshold dose. In actual practice the skin dose in interventional procedures varies over the body, and it is the dose to the area with highest skin dose (peak skin dose – PSD) that determines whether erythema is expected to occur.
