PHANTOMS AND DYNAMIC-RANGE IN MAMMOGRAPHY

The phantoms used to evaluate the imaging properties of a mammography system include details and/or test objects embedded in a bulk with a c onstant X ray transmission all over the image plane. On the other hand , the X ray beam transmitted by the breast presents a wide variation o f intensity in the image plane. An experimental method for evaluating the dynamic range (DR) of the breast by using a reference aluminium al loy step wedge and a frame grabber system is presented. The results of DR evaluation of 50 breast radiographs are analysed and discussed. On the basis of the dynamic range data, some criteria for designing phan toms with a planar distribution of the transmitted exposure similar to the transmission of an actual breast are presented.