Journal of X-Ray Science and Technology 22 (2014) 785–796 785 DOI 10.3233/XST-140463 IOS Press Detection of posteriorly located breast tumors using gold nanoparticles: A breast-mimicking phantom study Liqiang Ren a , Di Wu a , Laurie L. Fajardo b , Yuhua Li a , Bin Zheng a and Hong Liu a,∗ a Center for Bioengineering and School of Electrical and Computer Engineering, University of Oklahoma, Norman, OK, USA b Department of Radiology, University of Iowa, Iowa City, IA, USA Received 27 May 2014 Revised 6 September 2014 Accepted 25 September 2014 Abstract. BACKGROUND: Accurately depicting breast tumors located posteriorly, close to the chest wall musculature, with conven- tional mammography is a technical challenge. OBJECTIVE: This study demonstrates the proof of concept of an x-ray fluorescence mapping (XFM) technique to address this issue. METHODS: A tissue-equivalent gel phantom is designed to mimic structures in the central part of a compressed breast. The posterior aspect of the breast and adjacent pectoralis major muscle are represented by another 10-mm-thickness breast tissue simulation phantom (BR12) that is attached to the back of the gel phantom as a region of interest (ROI). Two gold nanoparticle (GNP) solutions are embedded into the ROI to simulate varying GNP uptake within breast lesions. The ROI is imaged through performing the XFM technique with an x-ray pencil-beam and a single spectrometer. RESULTS: A 2D mapping of the middle plane in the ROI demonstrates feasibility and matches well the known spatial distri- bution and different GNP concentrations. 3D reconstruction of the ROI is easily rendered by repeating the 2D mapping process. CONCLUSION: XFM system geometry and its insensitivity to attenuation coefficients of breast tissue components are unique characteristics that may complement conventional mammography and improve the detection of breast cancers located posteri- orly, adjacent to or overlying the chest wall musculature. Keywords: Breast cancer detection, posteriorly located breast tumors, chest wall musculature, breast-mimicking phantom, x-ray fluorescence mapping (XFM), gold nanoparticles (GNPs) 1. Introduction According to the latest cancer statistical data from the American Cancer Society 2014, breast cancer is ranked first in cancer incidence and second in cancer mortality rates in women of the United States. ∗ Corresponding author: Hong Liu, Center for Bioengineering and School of Electrical and Computer Engineering, University of Oklahoma, 101 David L Boren Blvd, Norman, OK 73019, USA. Tel.: +1 405 325 4286; Fax: +1 405 325 7066; E-mail: liu@ou.edu. 0895-3996/14/$27.50 c  2014 – IOS Press and the authors. All rights reserved