Contrast Agent Mammography Using Spectroscopic Detectors.

World Health Organization (WHO) reported that breast cancer is the top cancer in women both in the developed and the developing countries. Although breast cancer is thought to be a disease of the developed countries, the incidence of breast cancer is increasing in developing countries, where the disease has becoming the leading cause of death. WHO added that the high mortality rates in less developed countries is mainly causes by majority of cases are diagnosed in late stages preventing curable treatment, as well as by the lack of adequate diagnosis and treatment facilities. Therefore, early tumour detection is very important in breast cancer management being able to improve the surviving rate. Many techniques to improve the detection of tumours in the breast have been developed in the last few years. This study is focusing on the dual-energy technique of contrast-enhanced digital mammography (CEDM) to aid in the detection and characterization of breast lesions. Standard dual-energy (K-edge subtraction) methodology requires two separate acquisitions to obtain two images, below and above the K-edge of a given contrast agent, and is typically implemented with a monochromatic X-ray source. This work in mammography proposes an approach using a polychromatic beam, providing for clinical applications with X-ray tubes. In particular, with a polychromatic beam produced by a microfocal X-ray source, this work is aimed at assessing the feasibility of K-edge subtraction (KES) mammography carried out in conjunction with an iodine-based contrast agent. Spectroscopic information is obtained using pixellated spectroscopic detectors. Two separate acquisitions in the standard dual-energy technique implies increased patient dose with respect to a conventional procedure and potentially incorrect image registration due to patient motion. A spectroscopic detector allows simultaneous acquisition of the two images by integrating appropriate bands from the transmitted X-ray spectrum, thus removing the above limitations. Moreover, an appropriate choice of the integration bands allows optimization of image quality, resulting from a trade-off between background removal (achieved with a narrow band as the maximum difference in the attenuation coefficient of iodine on the two sides of the K-edge is fully exploited) and low statistical noise (achieved with a wide band). Images of a test object and a breast phantom (with a non-uniform background) with different detail sizes have been obtained simultaneously, above and below the K-edge of iodine (33.2 keV). Results obtained are presented for two different image subtraction algorithms: logarithmic subtraction and dual-energy linear combination in terms of detail visibility, quantified using the contrast-to-noise ratio (CNR). Effects of integrating different energy band widths, contrast agent concentration and entrance surface dose have been investigated for different detail size. Due to simultaneous acquisition, the dose is reduced and the images are free from motion artifacts. Whilst being conceptually simpler, logarithmic subtraction is strongly dependent upon the position and width of the band selected, while linear combination allows better background removal even with a wide energy band, and therefore better image quality (higher CNR). Sequence from that, the details visibility were compared to the results from conventional absorption imaging using a digital mammography unit to show the potential benefit of dual-energy imaging with a spectroscopic detector. With similar entrance dose, the results show better image quality for the spectroscopic detector. The above work has demonstrated the applicability of performing low-dose dual-energy imaging using a standard X-ray source and a spectroscopic detector. Later on, application of dual-energy technique to real-case scenarios were tested. By taking into account the theoretical considerations for using a lower iodine concentration, the results show image subtraction cannot be done with reasonable dose (and timescale) to get a clear visibility of the detail. However, further experiment with dynamic measurements show that the spectroscopic detector was able to image the detail with the timescale typical of an uptake and washout curve using full spectrum acquisition