M11-186 1 Abstract Diffraction Enhanced Breast Imaging could potentially give a significant increase in sensitivity and specificity compared to conventional transmission x-ray mammography. A device that may be promising for this application area is the Controlled-Drift Detector. The Controlled Drift Detectors feature a small pixel size, similar to Charge Coupled Devices, but are superior to Charge Couple Devices in certain key areas: (a) they can operate in photon counting mode measuring the energy with spectroscopic resolution, (b) very high frame rates are possible (up to 100 kHz) and (c) they can potentially be constructed to large area linear devices. The results of the first performance evaluation of the Controlled Drift Detector in its application to Diffraction Enhanced Breast Imaging are presented and discussed. Index Terms Controlled-Drift Detector, DEBI, X-ray imaging. I. INTRODUCTION HE use of X-rays in medical applications is usually limited to transmission imaging and scattered photons are considered a drawback that decreases the image contrast. However, scattered photons, differently from the primary transmitted beam, interact with the tissue under analysis and can therefore yield specific information on its molecular structure. This is of particular interest in the analysis of breast tissue. Conventional mammography is currently considered the most effective breast screening tool. However, it has Manuscript received January 23, 2007. This work was supported in part by INFN, Sezione di Milano and by a Marie-Curie Intra-European Fellowship within the 6th European Community Framework Programme under Grant No. MEIF-CT-2004-007206. Andrea Castoldi and Antonio Galimberti are with Dipartimento di Ingegneria Nucleare, Politecnico di Milano and INFN, Sezione di Milano, 20133 Milano, Italy (telephone +39 02 23996321, e-mail andrea.castoldi@polimi.it ). Chiara Guazzoni is with Dipartimento di Elettronica e Informazione, Politecnico di Milano and INFN, Sezione di Milano, 20133 Milano, Italy. (telephone: +39 02 23996147, e-mail: chiara.guazzoni@mi.infn.it ). Robert Hartmann is with PNSensor GmbH, and with f MPI Halbleiterlabor, Otto-Hahn-Ring 6, 81739 München, Germany. Silvia Pani and Gary Royle are with the Department of Medical Physics and Bioengineering, University College London, WC1E 6BT London, UK (e- mail: spani@medphys.ucl.ac.uk , groyle@medphys.ucl.ac.uk ). Lothar Strüder is with Max Planck Institut Halbleiterlabor, Otto-Hahn- Ring 6, München D-81739, Germany and with Max Planck Institut für Extraterrestriche Physik. He is also with Universität Siegen, FB Physik. drawbacks and alternative techniques are being sought for improving tissue discrimination. Mammograms vary in appearance by the amount and distribution of fat and fibro-glandular tissue. While a tumour can usually be easily detected in a predominantly fatty breast due to the large difference in the attenuation coefficients of the two tissue types, the detection of a tumour in a denser breast becomes difficult due to the small difference in the attenuation coefficients of carcinoma and fibroglandular tissue [1]. For this reason, alternative techniques are being sought for obtaining higher diagnostic accuracy, particularly for women with dense breasts.. Among these, Diffraction Enhanced Breast Imaging (DEBI) may be a promising alternative [2-5]. The main limitation of DEBI is the low yield of scattered photons for a given angular aperture. For this reason, the choice of a suitable detector is of crucial importance. In this paper we present the first results of an experimental evaluation of the Controlled-Drift Detector (CDD), a novel X- ray silicon imager, in its application to DEBI. Synchrotron radiation beams were used for testing the performance of the detector under several defined conditions, but DEBI is likely to be implemented also on conventional sources using a CDD. Section II reviews the advantages and constraints of DEBI and Section III highlights the basic features of the Controlled-Drift Detector and the advantages of its use in this analytical technique. Section IV is devoted to the assessment of the use of this novel detector type in Diffraction Enhanced Imaging through experimental measurements on phantoms. Section V presents the results of the application of Controlled-Drift Detectors to diffraction-enhanced imaging of biological tissues. Section VI ends with the indication of future developments. II. ADVANTAGES AND CONSTRAINTS OF DEBI Coherent scattering is described classically as the interaction between the electric field associated with the x-ray beam and the electric field associated with the electron charge distribution in the material [6]. The electrons are set oscillating and subsequently emit radiation of the same wavelength as the incident beam. In biological materials, coherent scatter becomes important at photon energies below 50 keV and, because of its sharply forward peaked nature; it is the dominant scattering process at small angles (up to 10°). Application of Controlled-Drift Detectors in Diffraction Enhanced Imaging of Tissues A. Castoldi, Member, IEEE, C. Guazzoni, Member, IEEE, A. Galimberti, R. Hartmann, S. Pani, G. Royle, and L. Strüder T