X-ray fluorescence computed tomography (XFCT) with nanoparticles (NPs) as contrast agents has reached technical maturity allowing for in vivo preclinical imaging in the laboratory setting. We present the first in vivo longitudinal study with XFCT where mice were 5 times each during an 8-week period. Imaging is performed with low radiation dose (<25 mGy) and high signal-to-background for high-spatial-resolution imaging (200-400 µm) of molybdenum NP accumulations (down to ~50 µg/ml Mo). We further discuss our ongoing development of protein-coated NPs for actively targeting molecular markers (e.g., cancer), as well as potential clinical applications.
X-ray fluorescence tomography (XFCT) using nanoparticles (NPs) as contrast agents shows promise for high-spatial- resolution 3D molecular imaging. The technique has been demonstrated experimentally on phantoms as well as in small animals, i.e., mice. Parallel to experimental development, simulations play a key role in investigating the performance of existing and proposed XFCT arrangements. Up until recently, however, realistic simulations of small-animal XFCT have been unavailable due to the lack of appropriate, accurate and accelerated Monte Carlo (MC) based tools.
We have developed the tools necessary to simulate highly realistic small-animal XFCT. Our MC tool, XRFGPU is based on the accelerated open-source MC-GPU and allows simulations with speeds >1000x faster than other existing MC codes capable of similar simulations. Using available high-resolution digital mouse phantoms, we can predict the performance of any XFCT imaging arrangement and produce the realistic data needed for future development of small-animal XFCT. Here we validate the simulations against our laboratory arrangement, capable of 200 μm spatial-resolution XFCT of mice. Comparisons using a phantom confirms that the simulations are accurate. Lastly, we compare simulated images with images acquired in vivo using our laboratory arrangement showing how simulations can be used to enhance the interpretation of experimental data.
XIPE, the X-ray Imaging Polarimetry Explorer, is a mission dedicated to X-ray Astronomy. At the time of
writing XIPE is in a competitive phase A as fourth medium size mission of ESA (M4). It promises to reopen the
polarimetry window in high energy Astrophysics after more than 4 decades thanks to a detector that efficiently
exploits the photoelectric effect and to X-ray optics with large effective area. XIPE uniqueness is time-spectrally-spatially-
resolved X-ray polarimetry as a breakthrough in high energy astrophysics and fundamental physics.
Indeed the payload consists of three Gas Pixel Detectors at the focus of three X-ray optics with a total effective
area larger than one XMM mirror but with a low weight. The payload is compatible with the fairing of the Vega
launcher. XIPE is designed as an observatory for X-ray astronomers with 75 % of the time dedicated to a Guest
Observer competitive program and it is organized as a consortium across Europe with main contributions from
Italy, Germany, Spain, United Kingdom, Poland, Sweden.
X-ray fluorescence tomography (XFCT) has potential for high-resolution 3D molecular x-ray bio-imaging. In this
technique the fluorescence signal from targeted nanoparticles (NPs) is measured, providing information about the spatial
distribution and concentration of the NPs inside the object. However, present laboratory XFCT systems typically have
limited spatial resolution (>1 mm) and suffer from long scan times and high radiation dose even at high NP
concentrations, mainly due to low efficiency and poor signal-to-noise ratio.
We have developed a laboratory XFCT system with high spatial resolution (sub-100 μm), low NP concentration and
vastly decreased scan times and dose, opening up the possibilities for in-vivo small-animal imaging research. The system
consists of a high-brightness liquid-metal-jet microfocus x-ray source, x-ray focusing optics and an energy-resolving
photon-counting detector. By using the source’s characteristic 24 keV line-emission together with carefully matched
molybdenum nanoparticles the Compton background is greatly reduced, increasing the SNR. Each measurement
provides information about the spatial distribution and concentration of the Mo nanoparticles. A filtered back-projection
method is used to produce the final XFCT image.