X-Ray Optics and Instrumentation 
Volume 2008 (2008), Article ID 635024, 8 pages
doi:10.1155/2008/635024
Research Article

A Tunable Energy Filter for Medical X-Ray Imaging

Erik Fredenberg,1 Björn Cederström,1 Magnus Åslund,2 Carolina Ribbing,3 and Mats Danielsson1

 1Department of Physics, Royal Institute of Technology, AlbaNova University Center, 106 91 Stockholm, Sweden
2Research & Development Department, Sectra Mamea AB, Smidesvägen 5, 171 41 Solna, Sweden
3Department of Engineering Sciences, The Ångström Laboratory, Uppsala University, 751 21 Uppsala, Sweden
Received 18 April 2008; Accepted 14 August 2008

Recommended by Doug Pfeiffer

Abstract

A multiprism lens (MPL) is a refractive X-ray lens, and its chromatic properties can be employed in an energy filtering setup to obtain a narrow tunable X-ray spectrum. We present the first evaluation of such a filter for medical X-ray imaging. The experimental setup yields a 6.6 gain of flux at 20 keV, and we demonstrate tunability by altering the energy spectrum to center also around 17 and 23 keV. All measurements are found to agree well with ray-tracing and a proposed geometrical model. Compared to a model mammography system with absorption filtering, the experimental MPL filter reduces dose 13–25% for 3–7 cm breasts if the spectrum is centered around the optimal energy. Additionally, the resolution is improved 2.5 times for a 5 cm breast. The scan time is increased 3 times but can be reduced with a slightly decreased energy filtering and resolution.