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TH‐AB‐204‐11: X‐Ray Fluorescence CT Induced by Proton Beam: Experiments and Simulations
Author(s) -
BazalovaCarter M,
Ahmad M,
Matsuura T,
Takao S,
Matsuo Y,
Fahrig R,
Shirato H,
Umegaki K,
Xing L
Publication year - 2015
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.4926178
Subject(s) - proton , x ray , beam (structure) , nuclear medicine , x ray fluorescence , physics , fluorescence , materials science , optics , medical physics , nuclear magnetic resonance , nuclear physics , medicine
Purpose: To demonstrate the feasibility of x‐ray fluorescence computed tomography induced with proton beams (pXFCT) for imaging of gold contrast agent by means of experiments and Monte Carlo (MC) simulations. Methods: A 7‐cm diameter water phantom containing 2.2‐cm diameter vials filled with gold solutions of 3–5% Au (percent weight concentration) was imaged with pXFCT using a 7‐mm FWHM 220‐MeV proton beam and a 3×3mm 2 CdTe photon‐counting detector. The phantom was imaged in 1st generation CT scanner geometry using a programmable rotation/translation stage and 21 translation steps separated by 3.3 mm and 36 rotation steps in 10° intervals. Each of the 756 x‐ray spectra was acquired for 20 s using 5×10 1 ⁰ incident protons with the CdTe detector placed at 45 cm from the isocenter and at 90° with respect to the proton beam. The 220 MeV proton beam was stopped in a solid water beam dump and the total imaging time was 4.2 hours. The experimental pXFCT data acquisition geometry was modeled based on the actual and a simplified geometry with the TOPAS MC code. pXFCT images were reconstructed based on experimental and MC‐simulated x‐ray spectra with filtered back‐projection using Kα peaks of gold. Results: All gold vials were visible in both the experimental and simulated pXFCT images. Contrast‐to‐noise ratio (CNR) of the 3% Au vial was 5.8 and 11.5 in the experimental and simulated pXFCT image, respectively. pXFCT detection limit of the experimental setup was determined to be 1.8% Au, which was twice as high as the MC‐simulated detection limit. Further MC simulations revealed that x‐ray scatter from the beam dump was the main contribution to x‐ray fluorescence signal contamination. Conclusion: We have demonstrated the feasibility of proton‐induced XFCT imaging of gold. We anticipate that pXFCT imaging sensitivity will be improved in an optimized pXFCT imaging system utilizing beam collimation.