CONSISTENCY OF 3-DIMENSIONAL PLANNING TARGET VOLUMES ACROSS PHYSICIANS AND INSTITUTIONS

Purpose: Three-dimensional treatment planning depends upon exact and c onsistent delineation of target volumes, This study tested whether dif ferent physicians from different institutions vary significantly in th eir creation of planning target volumes (PTVs), Methods and Materials: Eight physicians from three different institutions created partial pl anning target volumes for nine clinical test cases. Their target volum es were evaluated qualitatively and quantitatively. Quantitative resul ts were tested for significant differences. Results: Qualitative analy sis showed the physicians to vary in (a) the margin placed around the clinical target volume, (b) the margin used near critical structures, and (c) handling of concavities in the clinical target volume, Quantit ative analysis showed these variations to result in statistically sign ificant differences in the measured volume of the physicians' planning target volumes, Conclusions: Individual physicians and institutions d iffer significantly in their creation of planning target volumes, sugg esting individual and institutional differences in the working definit ion for the PTV, Implications of this fact are discussed, along with a reas where standardization can be improved. (C) 1997 Elsevier Science Inc.