The doses needed to produce erythema are very high indeed—if the skin is exposed to 200-kilovolt x rays at a high dose rate of 30 rad per minute, then erythema appears after about 20 minutes (or 600 rad) of exposure, and moist desquamation (equivalent to a third-degree burn) occurs after about 110 minutes (or about 2000 rad) of exposure. The loss of fingers, as shown in the photographabove, was sometimes the result. Such conditions are ultimately caused by outright killing of many cells. In the case above, dermal basal cells and blood vessels were critically injured in the fingers, scar tissue probably plugged the blood vessels and stopped the flow of blood. The loss of blood supply ultimately led to the death of tissue in the fingers and the loss of those extremities.