Optimized EDXRF system for simultaneous detection of gold and silver nanoparticles in tumor phantom

Abstract

An energy-dispersive X-ray fluorescence system (EDXRF) was optimized for simultaneous detection of gold and silver nanoparticles inside water-equivalent phantoms applied to theranostics. The optimization process was carried out in order to maximize the fluorescence detection, keeping dose levels as low as possible. Gold and silver fluorescent emissions were simultaneously detected emerging from phantom's volume, allowing the future development of multi-parametric imaging associated to specific tumor characteristics. For fluorescence detection, gold LIII-edge and silver K-edge emission lines were used, exited with a conventional X-ray source with a tungsten target. Several combinations of filters of different thickness were used to hardening the Bremsstrahlung spectrum, thus producing energetically narrow beams with central energy according to both excitation edges. In the case of gold, incident spectrum was optimized by means of strontium (Sr) and yttrium (Y) filters to relatively incrementing photons capable of exciting gold LIII-edge, while silver K-edge excitation was improved using a tin (Sn) filter. Filtering combinations made of 212.0 μm Sr with 94.5 μm Sn, and 130.2 μm Y with 94.5 μm Sn maximized fluorescence detection sensitivity and minimized delivered dose, resulting in doses 2.24 and 2.36 times lower than individual gold or silver fluorescent detection. Furthermore, when dual gold and silver fluorescent detection was performed, the minimum detectable concentration was lower than single element detection: 0.042 ± 0.002 mg/mL of Au and 0.024 ± 0.005 mg/mL of Ag in dual detection against 0.058 ± 0.003 mg/mL of Au and 0.124 ± 0.007 mg/mL of Ag when measured independently.