X-ray Fluorescence Imaging System Research Articles

TH-A-141-04: Localization and Quantification of Gold Nanoparticles Using L-Shell Fluorescence Imaging with a Benchtop X-Ray Source

Purpose: To develop a high sensitivity L-shell x-ray fluorescence imaging system that locates and quantifies sparse concentrations of gold nanoparticles (GNPs) using a polychromatic benchtop x-ray source. Methods: An L-shell x-ray fluorescence imaging system was built with a benchtop polychromatic x-ray source and a Si-PIN detector. Water-filled cylindrical tubes (12 mm in diameter) loaded with GNPs at 2%, 1%, 0.5%, 0.05%, and 0.005% GNP by weight were served as calibration phantoms. An imaging phantom was created using the same cylindrical tube but filled with water-equivalent gel containing structures mimicking GNP-loaded blood vessel and 1 cc tumor. The phantoms were irradiated by a 3-mm diameter 65 kVp x-rays filtered by 1 mm aluminum. Fluorescence/scatter photons from the phantoms were detected at 90° with respect to the beam direction using a Si-PIN detector with a pin-hole collimation. For the imaging phantom, the detector was translated horizontally and vertically in 0.3-mm steps to create a 2-D fluorescence image of the phantom. The net L-shell fluorescence signal from GNPs was extracted from background, and then corrected for detector efficiency and in-phantom attenuation using a fluorescence-to-scatter normalization algorithm. The corrected signal from the calibration phantoms was used to create a calibration curve showing a linear relationship between corrected fluorescence signal and GNP mass per image voxel. Results: The results suggest that the current setup can detect a GNP mass of 500 ng (or 0.5 ppm) contained within each image voxel (0.0173 cc). The 2-D fluorescence image properly correlated the known spatial distribution and amount of GNPs within the imaging phantom. Conclusion: L-shell fluorescence imaging can be a highly sensitive tool that has the capability of simultaneously imaging the spatial distribution and determining the local concentration of GNPs presented within ex-vivo samples and superficial tumors during pre-clinical small animal studies. Supported by NIH/NCI grant R01CA155446; NIH/NCI grant R01CA155446

Evolution of Fe based intermetallic phases in Al–Si hypoeutectic casting alloys: Influence of the Si and Fe concentrations, and solidification rate

Al–Si–Fe hypoeutectic cast alloy system is very complex and reported to produce numerous Fe based intermetallic phases in conjunction with Al and Si. This publication will address the anomalies of phase evolution in the Al–Si–Fe hypoeutectic casting alloy system; the anomaly lies in the peculiarities in the evolution and nature of the intermetallic phases when compared to the thermodynamic phase diagram predictions and past publications of the same. The influence of the following parameters, in various combinations, on the evolution and nature of the intermetallic phases were analyzed and reported: concentration of Si between 2 and 12.6 wt%, Fe between 0.05 and 0.5 wt% and solidification rates of 0.1, 1, 5 and 50 K s−1. Two intermetallic phases are observed to evolve in these alloys under these solidification conditions: the τ5-Al8SiFe2 and τ6-Al9Fe2Si2. The τ5-Al8SiFe2 phase evolves at all levels of the parameters during solidification and subsequently transforms into the τ6-Al9Fe2Si2 through a peritectic reaction when promoted by certain combinations of solidification parameters such as higher Fe level, lower Si level and slower solidification rates. Further, it is also hypothesized from experimental evidences that the θ-Al13Fe4 binary phase precludes the evolution of the τ5 during solidification and subsequently transforms into the τ6 phase during solidification. These observations are anomalous to the publications as prior art and simulation predictions of thermodynamic phase diagrams of these alloys, wherein, only one intermetallic phases in the τ6-Al9Fe2Si2 is predicted to evolve and be retained as the terminal phase at the end of solidification. Several analysis methods such as light optical microscope, scanning electron microscope equipped with a dual beam focused ion beam milling machine and energy dispersive X-ray diffraction system, transmission electron microscope equipped with high resolution digital imaging system, energy dispersive X-ray diffraction system, and high energy synchrotron beam source for nano-diffraction coupled with X-ray fluorescence imaging system was used in this study.

Performance of a gaseous detector based energy dispersive X-ray fluorescence imaging system: Analysis of human teeth treated with dental amalgam

Energy dispersive X-ray fluorescence (EDXRF) imaging systems are of great interest in many applications of different areas, once they allow us to get images of the spatial elemental distribution in the samples. The detector system used in this study is based on a micro patterned gas detector, named Micro-Hole and Strip Plate. The full field of view system, with an active area of 28×28mm2 presents some important features for EDXRF imaging applications, such as a position resolution below 125μm, an intrinsic energy resolution of about 14% full width at half maximum for 5.9keV X-rays, and a counting rate capability of 0.5MHz. In this work, analysis of human teeth treated by dental amalgam was performed by using the EDXRF imaging system mentioned above. The goal of the analysis is to evaluate the system capabilities in the biomedical field by measuring the drift of the major constituents of a dental amalgam, Zn and Hg, throughout the tooth structures. The elemental distribution pattern of these elements obtained during the analysis suggests diffusion of these elements from the amalgam to teeth tissues.

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Characterization of an energy dispersive X-ray fluorescence imaging system based on a Micropattern Gaseous Detector

An energy dispersive X-ray fluorescence (EDXRF) imaging system based on a Micropattern Gas Detector has already shown good results for different applications. An X-ray tube, a pinhole camera and a Micro-Hole and Strip Plate (MHSP) based detector are the main components of the experimental system. The detector uses an MHSP in a Xe atmosphere at 1 bar, and acting as a photon counting device, i.e., it is capable to record each single event retaining the energy and the interaction position (2D-sensitive detector) information of the incident photon, demonstrating to be a promising device for EDXRF imaging applications. This work presents studies of energy resolution, energy linearity and spatial resolution/elemental mapping as a function of image magnification of the system.