Schematic diagram of the experimental setup for measuring the penetrability of fluorescence x-rays from GNPs, including a polychromatic x-ray source, a pencil beam collimator, a 1 mm thick lead excitation filter (not used in this setup considering the emitted x-ray count rate), saline gold solutions (1.0%/0.5%/0.2% by weight), a compact integrated spectrometer system, and specifically, two spaces reserved to insert a combination of BR12 (1) for inserting BR12 on the excitation path; (2) for inserting BR12 on the emission path.
Schematic diagram of the geometrical setup in a standard Craniocaudal (CC) view; the distances from the focal spot of the x-ray source and the sensitive element of the spectrometer to point P of interest are determined based on engineering consideration, which are set to 147 mm and 107 mm, respectively in this study.
(a) spectrum with no BR12 blocks on either path; spectra with BR12 blocks on the excitation (70 mm)/emission (50 mm) path when using (b) 1.0%, (c) 0.5%, and (d) 0.2% gold solution.
Schematic diagram of the cuboid BR12 phantom with four cylindrical regions for 0.2%, 0.5%, and 1.0% gold solutions and water: (a) plane view; (b) 3D view (unit: mm).
Schematic diagram of the experimental setup for quantitatively mapping the designed phantom.
Schematic diagram of the XFM scanning process with moving steps of 5 mm in X, Y, and Z directions: (a) Example of scanning at position (12.5, 22.5, and 17.5); (b) Four planes in the scanning in Z direction.
Schematic diagram of the attenuation analysis of both the incident primary x-ray beam and isolated gold K α fluorescence counts.
Comparison of linear attenuation coefficients between water and BR12, with amplification of the energy range from 60 to 100 keV, where the data of the linear attenuation coefficients for BR12 and water are acquired from the specifications of BR12 and the National Institute of Standards and Technology (NIST, USA), respectively (Refs. 19,20 ).
The excitation spectrum of the incident x-ray beam used in this study; the energy from the K-edge of gold to 110 keV capable of exciting of the GNPs to produce K α is highlighted.
Six typical spectra obtained at representative positions within the phantom; two obvious K α peaks can be observed when gold solution is excited while its fluorescence x-rays is detected by the spectrometer: (a) 0.2% gold solution; (b) 0.5% gold solution; (c) 1.0% gold solution; while there is no fluorescence x-rays from GNPs can be detected: (d) 0.5% and 1.0% gold solution on the excitation path but no solution on the emission (receiving) path; (e) no gold solution on both the excitation and emission (receiving) paths; and (f) no gold solution on the excitation path but 1.0% and 0.2% gold solution on the emission (receiving) path.
Comparison of spectra when the excitation and emission paths are blocked by (a) water or (b) solution; (c) spectra comparison with relative average deviation (65 –70 keV) as low as 2.55% while Pearson correlation coefficients 0.999 (0–110 keV), 0.998 (40–85 keV), and 0.985 (65–70 keV).
(a) Diagram for background subtraction; background subtraction result for (b) 1.0% gold solution; (c) 0.5% gold solution; and (d) 0.2% gold solution.
Calibration map for each imaging plane within the BR12 phantom.
Reconstructed mapping results for four planes from top to bottom of the phantom with distance interval of 5 mm: (a) z = 17.5 mm; (b) z = 12.5 mm; (c) z = 7.5 mm; and (d) z = 2.5 mm.
Linear relationship between the average fluorescence counts and the concentrations of gold solutions.
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