Nuclear Instruments and Methods in Physics Research A 478 (2002) 95–97 Experimental test of a new technique of background suppression in digital mammography M.G. Bisogni a , S. Bottari b , M.A. Ciocci b , M.E. Fantacci a , P. Maestro b , N. Malakhov a , P.S. Marrocchesi b, *, M. Novelli a , M. Quattrocchi a , F. Pilo b , V. Rosso a , N. Turini b , S. Zucca a a University of Pisa, INFN-Pisa, Italy b University of Siena, Dipartimento di Fisica, 55 via Banchi di Sotto, 53100 Siena, Italy Abstract A multiple-exposure technique in digital mammography has been developed to suppress the physical background in the image due to Compton scattering in the body. A pair of X-ray masks, shaped in a projective geometry and positioned upstream and downstream the patient, are coupled mechanically and moved in four steps along a square pattern in order to irradiate the full area in four consecutive short exposures. A proof-of-principle apparatus is under test with a breast phantom and a standard mammographic X-ray unit. Results are reported. r 2002 Published by Elsevier Science B.V. Keywords: Digital radiography; Digital mammography 1. Introduction During the last decade, research in digital mammography has been strongly pursued in many countries leading to the development of state-of- the-art digital breast imaging systems [1]. Further improvement in transmission radiography can be obtained by suppression of the background in the image due to the diffused radiation from the body. The aim is to enhance our capability to visualize image details at low contrast where the resolution of the imaging system is limited by the exposure which has to be kept low to reduce the total dose (a key issue for mammographic screening). An innovative multiple-exposure technique for digital mammography [2], based on the use of a collimator and an anti-scatter grid coupled with a digital X-ray detector, was previously studied by our group using Monte Carlo techniques [3]. A pair of X-ray masks, shaped in a projective geometry and positioned upstream and down- stream the patient, are coupled mechanically and moved in four steps along a square pattern in order to irradiate the full area in four consecutive short exposures. The two grids are shaped as an array of 16 squared apertures (8.10 and 8.65mm side, respectively). The multiple-exposure method should eliminate most of the problems associated with a fixed grid (absorption, image artifacts) with *Corresponding author. Physics department, University of Siena, 53100 Siena, Italy. E-mail address: marrocchesi@pi.infn.it (P.S. Marrocchesi). 0168-9002/02/$-see front matter r 2002 Published by Elsevier Science B.V. PII:S0168-9002(01)01730-2