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Experimental Investigation of Gold L-Shell X-Ray Fluorescence Imaging Using 3-D Printed Phantoms

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S Yasar

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


TH-AB-708-5 (Thursday, August 3, 2017) 7:30 AM - 9:30 AM Room: 708

Purpose: We performed a series of phantom experiments to further refine our gold L-shell x-ray fluorescence (XRF)-based imaging technique for quantification of gold nanoparticle (GNP) distribution within superficial animal tumors, which could be of significance for preclinical studies of GNP-based nanomedicine.

Methods: XRF imaging of polymethyl methacrylate (PMMA) phantoms containing GNPs were performed using a 60 kVp x-ray slit beam (of various widths) filtered by 0.08 mm Cu plus 0.8 mm Al and silicon drift detector. Excitation beam was optimized for detection of gold L-shell XRF (Lα and Lβ peaks at 9.7 and 11.4 keV, respectively). Using square-shaped phantoms, XRF peak intensities were characterized and minimum detectable GNP concentration was determined for different attenuation depths and acquisition times. XRF images were corrected based on the object shape determined from Compton scatter signal at 30 keV. Phantoms were created using 3D-printer.

Results: The minimum detectable GNP concentration using gold L-shell XRF depended on excitation beam size, detector aperture size, signal acquisition time, and attenuation depth. With a slit beam of 2 mm width and 15 sec acquisition-time, the detection limit was ~10 parts per million (ppm) at 1-2 mm depth. To achieve the same ~10 ppm detection limit at deeper attenuation depths, acquisition time needed to be doubled approximately in every 1 mm increase of the attenuation depth. The method used to extract the object shape (which was then used for attenuation correction of XRF signal) was found generally applicable for XRF imaging of small objects with unknown geometry.

Conclusion: The currently investigated method is feasible for XRF imaging of objects (of size ~1 cm) containing GNPs (at concentrations as low as ~10 ppm) and attenuation correction of the XRF signal without a priori information about the shape of the object.

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

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