Calcification Detection Optimization in Dual Energy Mammography: Influence of the X-Ray Spectra

Abstract

Breast cancer may manifest as microcalcifications (μCs) in X-ray mammography. However, the detection and visualization of μCs are often obscured by the overlapping tissue structures. Dual-Energy imaging technique offers an alternative approach for imaging and visualizing μCs. With this technique, a high- and a low-energy image is acquired and their differences are used to “cancel” out the background tissue structures. In this report, various combinations of maximum tube voltages, 23-30kVp for low energy and 50- 60kVp for high energy, and filter thicknesses were examined in order to obtain quasi-monochromatic spectra. The filters applied to Tungsten (W) spectra were selected according to their K-edge (K-edge filtering). The impact of these imaging parameters on the calcification signal-to-noise ratio (SNR) for a fixed entrance exposure was studied. The optimization of the study was accomplished by the maximization of the calcification SNR (SNR_tc ≥ 3) and the minimization of the coefficient of variation of the incident photons, for the minimum μC size that can be detected. The best results were obtained from filtered spectra at 30kVp and 60kVp for low and high energy respectively. These spectra were filtered with 300 μm Cd and 800 μm Sm with mean energy values 23.9 and 42.2 keV for low and high energy respectively.