[Radio-Geometric consideration of basal indentation using phantoms and specimens].

With the aid of colon-polyp phantoms, basal indentation (BI) of polypoid lesions on double-contrast examinations of the colon was studied. Our findings indicated that BI is a function of radio-geometric projections and its morphology (arcuate, angular and trapezoid) depends on size, shape and surface pattern of a polypoid lesion. These findings were also substantiated by specimen and clinical radiography.