Multi-energy X-ray imaging for mammography

for BHPA Symposium 5-6 feb 2010 Corresponding author: bart.dierickx@caeleste.be Multi-energy X-ray imaging for mammography B. Dierickx, N. Buls, C. Bourgain, C. Breucq, J. Demey, B. Dupont, A. Defernez 1 Caeleste CVBA, Antwerp, Belgium 2 Universitair Ziekenhuis Brussel, Brussels, Belgium 3 Vrije Universiteit Brussel, Dept. ETRO, Brussels, Belgium Summary When photon counting will be applied to X-ray imaging, one will have the possibility to extract spectral information form the image. In this paper we anticipate this possibility by evaluating the diagnostic value of dual or triple energy X-ray specimen mammography. Introduction Dual-energy or multi-energy X-ray imaging is a recognized method to add information to an X-ray image. Applications range from medical diagnostics, bone densitometry, mammography [2] [4] [5] to border control security [1]. Widespread use in medical imaging is precluded mainly by the additional dose due to the double exposure. An alternative way to obtain multi-energy information in the X-ray image, is by classifying the photons as they arrive by energy contents. Photon counting X-ray imagers have been demonstrated [3] but are not mature mainly due to the high electronic complexity of the pixels and the associated high cost and low manufacturing yield. Color X-ray imaging X-ray absorption in matter has a strong spectral dependence. As X-ray absorption essentially depends on the element’s (atom’s) Z-number, one can by examination of the absorbed of transmitted spectrum deduce information on the relative concentration of the elements. H C N O Na Mg P S Cl K Ca Fe Blood Breast Water 0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 Blood Bone Breast Muscle Water Fat Figure 1 Left: comparative spectral absorption of X-rays in the most relevant biological elements. Right. Relative composition (weight%) of common biological tissues Experiment A large potential application domain of “color” X-ray imaging is screening mammography. In this application the radiation dose in the breast most critical. For transmitted through 10cm layer, normalized to 1g/cm3 after http://physics.nist.gov/PhysRefData/ 0% 5% 10% 15% 20% 25% 30% 35% 40% 45% 50% 100