Optimization of the sensitivity/doses relationship for a bench-top EDXRF system used for in vivo quantification of gold nanoparticles

Abstract

The present work is devoted to optimizing the sensitivity-doses relationship of a bench-top EDXRF system, with the aim of achieving a detection limit of 0.010 mg/ml of gold nanoparticles in tumor tissue (clinical values expected), for doses below 10 mGy (value fixed for in vivo application). Tumor phantoms of 0.3 cm3 made of a suspension of gold nanoparticles (15 nm AurovistTM, Nanoprobes Inc.) were studied at depths of 0–4 mm in a tissue equivalent cylindrical phantom. The optimization process was implemented configuring several tube voltages and aluminum filters, to obtain non-symmetrical narrow spectra with fixed FWHM of 5 keV and centered among the 11.2–20.3 keV. The used statistical figure of merit was the obtained sensitivity (with each spectrum at each depth) weighted by the delivered surface doses. The detection limit of the system was determined measuring several gold nanoparticles concentrations ranging from 0.0010 to 5.0 mg/ml and a blank sample into tumor phantoms, considering a statistical fluctuation within 95% of confidence. The results show the possibility of obtaining a detection limit for gold nanoparticles concentrations around 0.010 mg/ml for surface tumor phantoms requiring doses around 2 mGy.