Effect of field size on the reaction of pig skin to single doses of X rays

The important study by Hopewell and Young (1982) on the absence of field size effect in reactions of irradiated pig skin claims to give evidence contradicting that of clinical experience. The authors point out the lack of firm quantitative clinical data and the apparent absence of any detailed prospective clinical study. They imply that clinical field size formulae may not be based on firm facts and may, therefore, be invalid. However, if one considers clinical relevance, their study on pig skin reactions was performed under some experimental conditions which are not generally present in clinical practice: (1) The study is based on single dose fractions, and very little human data are available for single doses.