The resulting skin dose in two-view mammography examinations

The entrance surface dose (ESD) (skin dose) and its variation due to overlapping radiation fields at mammography have been experimentally investigated on patients during two-view mammography screening examinations of both breasts and on phantoms of silicon gel. Measurements were done using multiple thermoluminescence dosemeters for mapping the variations in absorbed dose at the surface of the breast phantoms. It was found that the total resulting skin dose at the reference point on the breast surface, described in the European Protocol [Zoetelief, Fitzgerald, Leitz and Sabel (European protocol on dosimetry in mammography. EUR 16263 (Luxemburg: EC), 1996)] after multiple exposure of patient's breasts during two-view, four exposures mammography screening examinations is approximately 50 % higher as compared with the skin dose at the same point measured during one single (CC) exposure. The dose distributions on the breast phantom surface were non-uniform and indicated areas of higher doses, which were related to the regions of the superimposed fields on the surface during the examinations. The dosimetric importance of the superposition of X-ray fields on the ESD is discussed.