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Development of An Effective Attenuation Correction Method for Gold L-Shell X-Ray Fluorescence Imaging

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M Ahmed

M Ahmed*, S Yasar , S Jayarathna , S Cho , The University of Texas MD Anderson Cancer Center, Houston, TX


TH-AB-708-3 (Thursday, August 3, 2017) 7:30 AM - 9:30 AM Room: 708

Purpose: To develop a method that corrects for attenuation of x-ray fluorescence (XRF) and the excitation/incident beam for XRF imaging of gold nanoparticle (GNP) distribution in small animal tumor.

Methods: A GEANT4 Monte Carlo model was developed to investigate XRF imaging based on detection of gold L-shell XRF from GNPs and validated with respect to a novel benchtop XRF imaging setup with 60 kVp polychromatic beam filtered by Cu plus Al filter. A simple semi-empirical method was devised using ratio of Lα (9.7 keV) and Lβ (11.4 keV) peak intensities to correct for attenuation of XRF after emission and ratio of total XRF to Compton scattered photon count to correct for attenuation of excitation beam.

Results: The results show that the ratio of Lα to Lβ peak intensity uniquely estimates the attenuation depth of scattered photons in a given material, as it depends neither on GNP concentration nor on attenuation of excitation beam. The corrected XRF signal corresponding to unattenuated excitation beam was found to be independent of depth and material density (of tissue-like media). On the other hand, the XRF signal can be corrected for attenuation of excitation beam by using a simple power law, where the exponent is independent of material density and GNP concentration. The applicability of the devised method, however, relies on the fact that the two XRF peaks have substantially different attenuation coefficients for the material in question. This implies that the method is suitable for L-shell XRF imaging in the case of GNPs, as the attenuation coefficient changes almost linearly in this energy range (< 25-30 keV).

Conclusion: The proposed method corrects gold L-shell XRF-based image for the attenuation of emitted XRF and excitation beam, thus allowing one to estimate concentration/location of GNPs without any prior knowledge of the density/shape of tissue-like media.

Funding Support, Disclosures, and Conflict of Interest: Supported by NIH grants R01CA155446 & R01EB020658

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