Hybrid X-ray Imaging Research Articles

Enhancing the Sensitivity and Spatial Imaging Resolution of a Hybrid X-Ray Imaging Screen via Energy Transfer at the ZnS (Ag) and a Thermally Activated Delayed Fluorescence Interface.

Novel scintillation materials have played an indispensable role in the recent remarkable progress witnessed for X-ray imaging technology. Herein, a high-performance X-ray scintillation screen was developed based on a highly efficient hybrid system combining inorganic ZnS (Ag) with thermally activated delayed fluorescence (TADF) scintillator materials via an interfacial energy transfer (EnT) mechanism. ZnS (Ag) has a high X-ray absorption capacity and functions as the initial layer for efficiently converting high-energy X-ray photons into low-energy visible light (acting as a sensitizer) while also serving as an energy donor. The TADF component, on the contrary, is an energy acceptor and forms an active scintillating layer. By harnessing TADF chromophores that can efficiently capture both singlet and triplet excitons, our composite material offers a remarkable spatial imaging resolution of 24 line pairs per millimeter, surpassing those of the majority of existing organic and inorganic scintillators. Further, our interfacial energy transfer strategy effectively amplifies the radioluminescence intensity of the TADF scintillator by a factor of 75, offering an outstanding light yield of 38,000 photons/MeV. This advancement represents a remarkable breakthrough in organic X-ray scintillation technology and is a notable achievement within the X-ray imaging field, paving the way for novel applications in medical imaging and security inspection.

Development of the detector simulation framework for the Wideband Hybrid X-ray Imager onboard FORCE

FORCE is a Japan–US space-based astronomy mission for an X-ray imaging spectroscopy in an energy range of 1–80 keV. The Wideband Hybrid X-ray Imager (WHXI), which is the main focal plane detector, will use a hybrid semiconductor imager stack composed of silicon and cadmium telluride (CdTe). The silicon imager will be a certain type of the silicon-on-insulator (SOI) pixel sensor, named the X-ray pixel (XRPIX) series. Since the sensor has a small pixel size (30–36 μm) and a thick sensitive region (300–500 μm), understanding the detector response is not trivial and is important in order to optimize the camera design and to evaluate the scientific capabilities. We have developed a framework to simulate observations of celestial sources with semiconductor sensors. Our simulation framework was tested and validated by comparing our simulation results to laboratory measurements using the XRPIX 6H sensor. The simulator well reproduced the measurement results with reasonable physical parameters of the sensor including an electric field structure, a Coulomb repulsion effect on the carrier diffusion, and arrangement of the degraded regions. This framework is also applicable to future XRPIX updates including the one which will be part of the WHXI, as well as various types of semiconductor sensors.

OA196] First experimental validation of phase-attenuation hybrid X-ray imaging

Purpose We propose a technique for the characterization of tissues, based on a hybrid phase contrast-attenuation imaging. The technique, first introduced in [1] , makes use of a method for material basis decomposition proposed by Alvarez and Macovski [2] . We present a semi-analytical simulation of the imaging process, as well as a preliminary implementation on a set of radiographic images of a dedicated phantom. Methods The phantom consists in a thin plastic plate composed of two “soft” materials, arranged in such a way to create a faint pattern of decreasing radiographic contrasts. The imaging was performed using synchrotron radiation (i.e. a quasi-parallel, monochromatic and coherent X-ray beam) and placing the phantom at different distances from the detector, so as to enhance the contribution of phase contrast. The images were acquired at the SYRMEP beamline of the Elettra synchrotron facility (Trieste, Italy). Results The reconstructed composition of the phantom was compared to the results of the semi-analytical simulation, showing a good agreement with the theoretical expectations. In particular, the technique proved able to enhance the visibility of faint contrasts with respect to the standard attenuation-based imaging. Moreover, it provided a precise quantitative estimate of the local composition of the imaged phantom. Conclusions The application of the basis decomposition method to the context of phase contrast imaging allows an effective rendering of a broad spectrum of radiographic patterns, from low frequency textures (which are captured by the attenuation effects) to high frequency details (highlighted by the phase shift effects). In addition, thanks to the simultaneous enforcement of two separate imaging channels, it also allows a two-component reconstruction of the imaged object.

Hard X-ray imaging mission NeXT

One of the major fields, which should be explored following Chandra and XMM-Newton is the hard X-ray sky up to several tens of keV with certain imaging capabilities. A new X-ray telescope mission or Non-thermal Energy eXploration Telescope (NeXT) in Japan is the first satellite mission proposed for a hard X-ray telescope using multilayer supermirror. The hybrid X-ray imager will be placed on the focal plane to observe hard X-ray images with CdTe pixel detector underneath a thin CCD for soft X-ray imaging. For high-resolution spectroscopy, TES type calorimeters are considered without cryogen. Non-imaging hard X-ray and soft gamma-ray detector is studied to achieve unprecedented sensitivity. NeXT will be a sort of pathfinder of hard X-ray astronomy not only technically but also scientifically.

Performance of back supportless CCDs for the NeXT mission

New X-ray Telescope (NeXT) will be the next Japanese X-ray astronomical satellite, which will be launched around 2010. A multilayer super mirror will give NeXT a large effective area across the 0.1–80 keV band. This wide bandpass requires a focal plane detector that is also sensitive along the entire energy band. As the focal plane detector for NeXT, we have been developing a Wideband hybrid X-ray Imager (WXI) consisting of X-ray CCDs and pixelized CdTe detector. The X-ray CCD of the WXI is required to maintain high quantum efficiency up to the high-energy band while allowing hard X-rays to pass undetected through the depletion (sensitive) layer. In order to meet these requirements, we have been developing a back supportless CCD (BS-CCD) which has a thick depletion layer, a thinned Si wafer and a back supportless structure. As the first step, we manufactured a test model of BS-CCD in order to (1) learn the handling and thinning process and (2) confirm that there is no change of the performance. For the mechanical strength and the safe handling of the wafer, we decided to thin the wafer to ∼ 200 μ m . We verified the thickness of the depletion layer and wafer of the BS-CCD to be about 70 and 190 μ m , respectively. The energy resolution at 5.9 keV of 144 eV and the read-out noise of 7 electrons (rms) are equal to those of an un-thinned CCD, hence, we confirmed that our thinning process has no effect on the performance.

A hybrid X-ray imaging spectrometer for NeXT and the next generation X-ray satellite

We propose a new type of wide band X-ray imaging spectrometer as a focal plane detector of the super mirror onboard on future X-ray missions including post Astro-E2. This camera is realized by the hybrid of back illumination CCDs and a back supportless CCD for 0.05–10 keV band, and a Micro Pixel Gas Chamber detecting X-rays at 10–80 keV.