KEYWORDS: Photons, Fluorescence, Iodine, X-ray fluorescence spectroscopy, In vivo imaging, Fluorescence imaging, Compton scattering, Cancer detection, Biological imaging, X ray detectors
X-ray fluorescence imaging (XFI) is a non-invasive technique enabling key applications such as pharmacokinetic studies and immune cell tracking. Labeling with medium to heavy elements enables detection by excitation with hard x-rays and subsequent measurement of emitted characteristic radiation. XFI provides high spatial resolution, high sensitivity and provides quantitative data. Special requirements need to be fulfilled by the x-ray detectors to reach a high sensitivity. These include high energy resolution, detection efficiency, large active area, and throughput, while minimizing noise from internal detectors effects. Here we discuss recent XFI applications in preclinical imaging and experiences with various detector types.
X-ray fluorescence imaging (XFI) provides the non-invasive tracking of entities like immune cells using dedicated markers in objects of different sizes. XFI typically uses synchrotron pencil beams to reach a high spatial resolution. To minimize the applied dose and scan time, a coarse scan can precede a finer one. A unique approach utilizing Bragg reflection at a cylinder optic with mosaic graphite-based material significantly enlarges the fine x-ray beam. Experiments at the P21.1 beamline at PETRA III synchrotron reveal a remarkable beam enlargement of 10 to 20 times, showcasing a 68% dose reduction and 62% scanning time reduction. This innovative technique holds promise for efficient and low-dose XFI applications.
X-ray fluorescence imaging (XFI) is a new promising imaging method for in vivo localization of low amounts of functionalized gold-nanoparticles (GNPs), enabling early cancer diagnostics and pharmacokinetic tracking studies. At the moment, XFI is not applicable for human-scales, since the modality suffers from an intrinsic high background caused by multiple Compton scattering processes. However, this limitation can be overcome by the use of highly brilliant X-rays combined with advanced filtering schemes. Recent developments in high power laser technology offer the potential to develop very compact X-ray sources by combining laser-wakefield acceleration (LWFA) and Thomson scattering (TS). Such a source is capable of providing high flux X-ray beams in the desired energy range around 100 keV, an energy that is high enough to penetrate through the body and is absorbed by GNPs. Further advantages are the tunability and the all-optical realization of the source, making it compact enough to transfer XFI into clinical practice. To measure the outcoming X-rays, detectors with high efficiency and energy resolution at the desired energies are needed, ideally pixelated, spectroscopic devices. Furthermore, necessary improvements to get the best parameters for the electron and laser beam, are discussed, including the implementation of active plasma lenses. Those devices focus the electron beams onto the interaction point with the scattering laser, enhancing the X-ray source as demonstrated in simulations.
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