Dermatologic radiotheraphy: selection of radiation qualities and treatment techniques.

The penetration of x-rays should be correlated the depth of the pathological process. The introduction of the "half-value depth" (D1/2) as a guidline in the selection of radiation qualities has greatly simplified cutaneous radiotherapy. Modern dermatologic x-ray units with beryllium windows operated between 10 and 50 (or 100 kV, offer the widest spectrum of radiation qualities suitable for dermatologic therapy, although older types of radiation equipment are still useful for most dermatology indications. Previous risks in dermatologic radiation therapy have been reduced to a large degree by the introduction of new sophisticated safety devices and by a deliberate reduction of unnecessary variations in the selection of physical factors. Beryllium window machine can be operated without changing milliamperage, target-skin distance or dose rate for different indications. The recommended standardization of physical factors offers a safer and easier alternative to previous techniques.