European Journal of Radiology 60 (2006) 275–278 Short communication Single-shot dual-energy subtraction mammography with electronic spectrum splitting: Feasibility Hans Bornefalk a, ∗ , John M. Lewin b , Mats Danielsson c , Mats Lundqvist c a Department of Physics, KTH, SE-100 44 Stockholm, Sweden b Diversified Radiology of Colorado, P.C., 938 Bannock Street, Suite 300, Denver, CO 80204, USA c Sectra Mamea AB, Kistag˚ angen 2, SE-164 40 Stockholm, Sweden Received 26 April 2006; received in revised form 30 July 2006; accepted 3 August 2006 Abstract We present a single-shot dual-energy subtraction mammography technique using an energy sensitive photon counting detector. An electronic threshold near the middle of the X-ray spectrum discriminates between high- and low-energy photons, and allows the simultaneous acquisition of high- and low-energy images which can be combined to suppress anatomical clutter. By setting the electronic threshold close to 33.2keV (the k-edge of iodine) the system is optimized for dual-energy contrast-enhanced imaging of breast tumors. This method eliminates the need for separate exposures which might otherwise lead to motion artifacts. The method is illustrated in phantom images. © 2006 Published by Elsevier Ireland Ltd. Keywords: Dual-energy imaging; Digital mammography; Contrast-enhancement; Physics; Breast; Breast-diagnosis; Breast radiography; Technology 1. Introduction The neovascularity accompanying tumor growth above a cer- tain size (a few millimeters) often results in increased permeabil- ity of the blood vessels [1]. The intravenous administration of iodinated contrast agent will lead to an increased concentration of iodine in and around the tumor. As the attenuation of iodine is much higher than for breast tissue, this will result in more readily visible tumors regardless of any additional techniques applied. Two additional techniques can be applied to increase de- tectability and classification of tumors when contrast agents is used in digital mammography: the first is the temporal subtrac- tion method based on first obtaining a pre-contrast image and then one or several post-contrast images. By means of loga- rithmic subtraction, areas where iodine has accumulated can be identified [2,3] and the difference in kinetics of the enhance- ment (speed of take-up and wash-out of the contrast agent) can be used to differentiate malignant abnormalities from benign [4]. ∗ Corresponding author. Tel.: +46 8 6127312. E-mail addresses: bornefalk@particle.kth.se(H. Bornefalk), jlewin@divrad.com(J.M. Lewin), ma-dan@sectra.se(M. Danielsson), ma-lun@sectra.se(M. Lundqvist). The second method is contrast-enhanced dual-energy sub- traction imaging [5–7]. With this method, two post-contrast im- ages are obtained using different X-ray spectra. By obtaining separate high- and low-energy images of the breast, the dif- ference in attenuation from different glandularity fractions is suppressed by subtracting a fraction of the logarithm of the low- energy image from the logarithm of the high-energy image. The resulting image will preferentially show areas where the uptake of the contrast agent has been intense. Lewin et al. [7] demon- strate that this method, using standard iodinated contrast agent, has the potential to better detect breast cancer tumors in clini- cal settings. The benefit of the second method over the first is a shorter acquisition time and thus less chance of motion arti- facts as the breast does not have to be decompressed (partially released from the compression paddles) while contrast agent is being administered. Whether temporal subtraction imaging (method one) or dual- energy imaging (method two) is best is an open question, but this technical note focuses on the dual-energy tissue cancella- tion method applied to contrast-enhanced tumors as described by Lewin et al. [7] However, instead of two exposures using X- ray spectra generated by two different tube voltages, the high- and low-energy images are acquired simultaneously. This can be obtained by having an energy threshold in the photon count- ing energy sensitive detector around the k-edge of iodine. This eliminates the need for two exposures and reduces the risk of 0720-048X/$ – see front matter © 2006 Published by Elsevier Ireland Ltd. doi:10.1016/j.ejrad.2006.08.004