Dirac-cone-like electronic states on nematic antiferromagnetic FeSe and FeTe.

We investigate the Dirac-cone-like (DCL) topological electronic properties of nematic-like antiferromagnetic (AFM) states of monolayer FeSe and FeTe designed artificially through first-principles calculations and Wannier-function-based tight-binding (WFTB) method. Our calculations reveal most of them have a pair of DCL bands on the Γ-Xline in the Brillouin zone (BZ) near the Fermi level and open a gap of about 20 meV in the absence and presence of spin-orbit coupling (SOC), respectively, similar to the lowest-energy pair-checkerboard AFM FeSe. We further confirm that they are weak topological insulators based on nonzeroZ2and fragile surface states, which are calculated by the WFTB method. For FeSe and FeTe in pair-checkerboard AFM states, we find that the in-plane compression strain in a certain range can give rise to another pair of DCL bands located on the Γ-X' line in the BZ. In addition, the magnetic moments, energies, and Fe-Se/Te distances for various nematic-like AFM configurations are presented. These calculations the combining effect of magnetism and topology in a single material and the understanding of the superconducting phenomena in iron-based FeSe and FeTe.

Magnetic field effect on topological properties of Dirac semimetals PdTe2/PtTe2/PtSe2.

We investigated magnetic field effect on the topological properties of transition metal dichalcogenide Dirac semimetals (DSMs) PdTe2/PtTe2/PtSe2based on Wannier-function-based tight-binding (WFTB) model obtained from first-principles calculations. The DSMs PdTe2/PtTe2/PtSe2undergo a transition from DSMs into Weyl semimetals with four pairs of Weyl points (WPs) in the entire Brillouin zone by splitting Dirac points under external magnetic fieldB. The positions and energies of WPs vary linearly with the strength of theBfield under thec-axis magnetic fieldB. Under thea- andb-axisBfield, however, the positions of magnetic-field-inducing WPs deviate slightly from thecaxis, and theirkzcoordinates and energies change in a parabolic-like curve with the increasingBfield. However, the system opens an axial gap on theA-Γ axis, and the gap changes with the direction of theBfield when the out ofc-axisBfield is applied. When we further apply the magnetic field in theac,bc, andabplanes, the results are more diverse compared to the axial magnetic field. Under theacandbcplaneBfield, thekzand energies of WPs within angleθ= [0°, 90°] andθ= [90°, 180°] are mirror symmetrically distributed. The distribution of WPs shows broken rotational symmetry under theabplaneBfield due to the difference of non-diagonal part of Hamiltonian. Our theoretical findings can provide a useful guideline for the applications of DSM materials under external magnetic field in the future topological electronic devices.

[The application of quantitative analysis of EBV DNA loads in plasma and peripheral blood mononuclear cells in Epstein-Barr Virus infection-related diseases in children].

Objective: To explore the correlation of EBV DNA load in two different types of plasma and peripheral blood mononuclear cells (PBMCs) in children with Epstein-Barr Virus (EBV) infection diseases. Methods: A retrospective evaluated was performed on EBV DNA quantification in plasma and PBMCs by qPCR between April, 2019 and December, 2020. The samples were collected from children of 456 cases with EBV infection and 2 306 healthy cases. In EBV infection group, boys were 253 and girls were 203, aged from 8 days to months to 16 years. In healthy group, boys were 1 267 and girls were 1 039, aged from 8 days to 16 years. Results: Infectious mononucleosis (IM) was the most common disease associated with EBV infection 73.68%(336/456). The detection rate of plasma and PBMCs in EBV infection group was 91.89% (419/456)and 99.34% (453/456)respectively, and was 100%(456/456) in plasma or PBMCs. The detection rate of plasma and PBMCs in healthy group was 1.13%(26/2 306) and 30.01%(715/2 306), respectively. Levels of EBV DNA in plasma and PBMCs in EBV infection group [IM, acute infections, pneumonia, post-transplantation lymphoproliferative disorder (PTLD), hemophagocytic lymphohistiocytosis, tonsillitis and lymphadenitis] was significantly higher than those in healthy group (In plasma, Z=-47.18,-34.41,-33.40,-31.71,-24.38,-20.86 and -20.59,respectively; In PBMCs, Z=-33.17,-16.45,-11.33,-9.45,-5.57,-5.16 and -5.45, respectively; P<0.05). In IM group, EBV DNA load in plasma and PBMCs in remission stage was significantly lower than those in infection stage (Z=-11.45, -8.53;P<0.05). In PTLD group, there was significant difference in EBV DNA load in plasma between infection and remission stage (Z=-4.13, P<0.05), while there was no significant difference in EBV DNA load in PBMCs (Z=-0.817, P>0.05). Conclusions: EBV infection was mainly caused by IM. Combined detection of plasma and PBMCs in EBV DNA is valuable for improving diagnosis ability of EBV infection-related diseases, and the load of EBV DNA could be used as a marker.

Energy-modulated x-ray fluorescence and luminescence emissions from therapeutic nanoparticles.

In this study, we have investigated the possibility of modulating x-ray fluorescence (XF) and x-ray luminescence (XL) emissions from therapeutic nanoparticles (NPs) by fine-tuning the energy of incident x-rays from benchtop x-ray sources. We have carried out detailed experimental studies to determine the strength of XF and XL emissions from Y2O3:Eu3+ and LaF3:Tb3+ NPs being irradiated with x-rays from benchtop x-ray sources operated with different tube-voltages and coupled to various filter configurations. These studies demonstrated that low-energy x-rays with average energy at around 10-15 keV are the most efficient to stimulate XL emission from the Y2O3:Eu3+ and LaF3:Tb3+ NPs. The efficiency falls quickly when x-ray energies go above or below the optimum energy range. As one would expect, x-rays with average energy just above the corresponding absorption edge of the target metal would be the most efficient in inducing XF emission. In this study, we have also demonstrated that one could fine-tune the incident x-ray energy to modulate the XL and XF emissions, such as (a) selectively inducing either XL or XF emission from the same type of NPs, (b) inducing preferential XL activation of Y2O3:Eu3+ over LaF3:Eu3+ or controlling the ratio of XL activation of these two types of NPs, and (c) introducing preferential XF emission from one type of NPs over the other. As a potential application, one could optimize the energy-characteristics of the incident x-rays to facilitate multiplexed combinatorial delivery of photodynamic therapy (X-PDT), where different agents could be administrated and then selectively activated in user-defined spatial and temporal patterns to fulfill combinatorial therapeutic effects. The understanding gained through this study could prove critical for enhancing the therapeutic delivery in X-PDT, and for attaining high-quality x-ray fluorescence computed tomography (XFCT) and x-ray luminescence computed tomography (XLCT) images while minimizing the x-ray dose to the sample.

Hybrid Pixel-Waveform (HPWF) Enabled CdTe Detectors for Small Animal Gamma-Ray Imaging Applications.

This paper presents the design and preliminary evaluation of small-pixel CdTe gamma ray detectors equipped with a hybrid pixel-waveform (HPWF) readout system for gamma ray imaging applications with additional discussion on CZT due to its similarity. The HPWF readout system utilizes a pixelated anode readout circuitry which is designed to only provide the pixel address. This readout circuitry works in coincidence with a high-speed digitizer to sample the cathode waveform which provides the energy, timing, and depth-of-interaction (DOI) information. This work focuses on the developed and experimentally evaluated prototype HPWF-CdTe detectors with a custom CMOS pixel-ASIC to readout small anode pixels of 350 µm in size, and a discrete waveform sampling circuitry to digitize the signal waveform induced on the large cathode. The intrinsic timing, energy, and spatial resolution were experimentally evaluated in this paper in conjunction with methods for depth of interaction (DOI) partitioning of the CdTe crystal. While the experimental studies discussed in this paper are primarily for evaluating HPWF detectors for small animal PET imaging, these detectors could find their applications for ultrahigh-resolution SPECT and other imaging modalities.

Element Mapping in Organic Samples Utilizing a Benchtop X-Ray Fluorescence Emission Tomography (XFET) System.

X-ray fluorescence computed tomography (XFCT) is an emerging imaging modality that maps the three-dimensional distribution of elements, generally metals, in ex vivo specimens and potentially in living animals and humans. Building on our previous synchrotron-based work, we experimentally explored the use of a benchtop X-ray fluorescence computed tomography system for mapping trace-metal ions in biological samples. This system utilizes a scanning pencil-beam to stimulate the object and then relies on a detection system, with single or multiple slit apertures placed in front of position-sensitive X-ray detectors, to collect the fluorescence X-rays and to form 3-D elemental map without the need for tomographic imaging reconstruction. The technique was used to generate images of the elemental distributions of a triple-tube phantom and an osmium-stained zebrafish.

Inter- and Intra-individual Variability in the Pharmacokinetics of Agomelatine Tablets in Chinese Healthy Male Subjects.

Agomelatine is an antidepressant with a unique action mechanism differing from conventional antidepressants. The high inter- and intra-individual variability of agomelatine was previously reported, but no exact data values about the inter- and intra-individual variability in AUC and Cmax were mentioned. The current study aimed to determine and evaluate the inter- and intra-individual variability in AUC and Cmax of agomelatine tablets in Chinese healthy male subjects, providing useful information for designing bioequivalence studies of agomelatine. Each of 12 Chinese healthy male subjects received a 25-mg agomelatine tablet on 2 separate periods, and plasma samples were collected up to 24 h after dose and analyzed for agomelatine. Inter- and intra-individual variability in the pharmacokinetic parameters (Cmax, AUC0-t and AUC0-∞) of agomelatine was assessed. High variations in the plasma concentrations of agomelatine could be observed at each sampling time between the different subjects and in one subject on different periods. The inter-individual CVs of Cmax, AUC0-t and AUC0-∞ were 102.20%, 131.74% and 130.59%, respectively. The intra-individual CVs of Cmax, AUC0-t and AUC0-∞ were 84.34%, 49.61% and 50.83%, respectively. The results showed high inter- and intra-individual variability in the pharmacokinetics of agomelatine in Chinese healthy male subjects, and the intra-individual variability at CV>80% should be considered in the design of bioequivalence studies.

Performance assessment of the single photon emission microscope: high spatial resolution SPECT imaging of small animal organs.

The single photon emission microscope (SPEM) is an instrument developed to obtain high spatial resolution single photon emission computed tomography (SPECT) images of small structures inside the mouse brain. SPEM consists of two independent imaging devices, which combine a multipinhole collimator, a high-resolution, thallium-doped cesium iodide [CsI(Tl)] columnar scintillator, a demagnifying/intensifier tube, and an electron-multiplying charge-coupling device (CCD). Collimators have 300- and 450-µm diameter pinholes on tungsten slabs, in hexagonal arrays of 19 and 7 holes. Projection data are acquired in a photon-counting strategy, where CCD frames are stored at 50 frames per second, with a radius of rotation of 35 mm and magnification factor of one. The image reconstruction software tool is based on the maximum likelihood algorithm. Our aim was to evaluate the spatial resolution and sensitivity attainable with the seven-pinhole imaging device, together with the linearity for quantification on the tomographic images, and to test the instrument in obtaining tomographic images of different mouse organs. A spatial resolution better than 500 µm and a sensitivity of 21.6 counts·s-1·MBq-1 were reached, as well as a correlation coefficient between activity and intensity better than 0.99, when imaging 99mTc sources. Images of the thyroid, heart, lungs, and bones of mice were registered using 99mTc-labeled radiopharmaceuticals in times appropriate for routine preclinical experimentation of <1 h per projection data set. Detailed experimental protocols and images of the aforementioned organs are shown. We plan to extend the instrument's field of view to fix larger animals and to combine data from both detectors to reduce the acquisition time or applied activity.

Performance assessment of the single photon emission microscope: high spatial resolution SPECT imaging of small animal organs

The single photon emission microscope (SPEM) is an instrument developed to obtain high spatial resolution single photon emission computed tomography (SPECT) images of small structures inside the mouse brain. SPEM consists of two independent imaging devices, which combine a multipinhole collimator, a high-resolution, thallium-doped cesium iodide [CsI(Tl)] columnar scintillator, a demagnifying/intensifier tube, and an electron-multiplying charge-coupling device (CCD). Collimators have 300- and 450-µm diameter pinholes on tungsten slabs, in hexagonal arrays of 19 and 7 holes. Projection data are acquired in a photon-counting strategy, where CCD frames are stored at 50 frames per second, with a radius of rotation of 35 mm and magnification factor of one. The image reconstruction software tool is based on the maximum likelihood algorithm. Our aim was to evaluate the spatial resolution and sensitivity attainable with the seven-pinhole imaging device, together with the linearity for quantification on the tomographic images, and to test the instrument in obtaining tomographic images of different mouse organs. A spatial resolution better than 500 µm and a sensitivity of 21.6 counts·s-1·MBq-1 were reached, as well as a correlation coefficient between activity and intensity better than 0.99, when imaging 99mTc sources. Images of the thyroid, heart, lungs, and bones of mice were registered using 99mTc-labeled radiopharmaceuticals in times appropriate for routine preclinical experimentation of <1 h per projection data set. Detailed experimental protocols and images of the aforementioned organs are shown. We plan to extend the instrument's field of view to fix larger animals and to combine data from both detectors to reduce the acquisition time or applied activity.

SPECT system optimization against a discrete parameter space.

In this paper, we present an analytical approach for optimizing the design of a static SPECT system or optimizing the sampling strategy with a variable/adaptive SPECT imaging hardware against an arbitrarily given set of system parameters. This approach has three key aspects. First, it is designed to operate over a discretized system parameter space. Second, we have introduced an artificial concept of virtual detector as the basic building block of an imaging system. With a SPECT system described as a collection of the virtual detectors, one can convert the task of system optimization into a process of finding the optimum imaging time distribution (ITD) across all virtual detectors. Thirdly, the optimization problem (finding the optimum ITD) could be solved with a block-iterative approach or other nonlinear optimization algorithms. In essence, the resultant optimum ITD could provide a quantitative measure of the relative importance (or effectiveness) of the virtual detectors and help to identify the system configuration or sampling strategy that leads to an optimum imaging performance. Although we are using SPECT imaging as a platform to demonstrate the system optimization strategy, this development also provides a useful framework for system optimization problems in other modalities, such as positron emission tomography and x-ray computed tomography (Moore et al (2009 IEEE Nucl. Sci. Symp. Conf. Rec. pp 4154-7), Freed et al (2008 Med. Phys. 35 1912-25)).

Protective effects of melatonin against oxidative stress in flow cytometry-sorted buffalo sperm.

Previous reports of the ability of melatonin to scavenge a variety of toxic oxygen and nitrogen-based reactants suggest that melatonin could be an effective antioxidant for protecting sperm. In this study, flow cytometry and laser tweezers Raman spectroscopy were used to evaluate the effect of melatonin on buffalo sperm quality to optimize sperm sex-sorting procedures. In fresh sperm incubated in the presence or absence of melatonin (10(-4) m) for 1, 24, 48 h or 72 h at 27°C, the mitochondrial activity was significantly higher than in a non-melatonin control (p < 0.05). Also, during the flow-sorting process, sperm in melatonin-supplemented groups had higher (p < 0.05) mitochondrial activity than the control. The intensity of Raman spectra from sperm frozen in media supplemented with melatonin was significantly weaker than that for non-melatonin-treated groups, except for a band at 1302 per cm. Thus, melatonin helps to protect buffalo sperm from reactive oxygen species induced by staining, sorting and freezing and increases semen quality after the freezing-thawing processes. Furthermore, the results indicate the high potential of the laser tweezers Raman spectroscopy technique for rapid, effective and non-invasive assessment of the quality of sperm cells.

First imaging result with an ultrahigh resolution stationary MR compatible SPECT system.

In this paper, we will present the design and preliminary performance of an ultrahigh resolution stationary MR compatible SPECT (MRC-SPECT) system that is developed in our lab. The MRC-SPECT system is based on the second-generation energy-resolved photon-counting (ERPC) CdTe detectors and there are several key features associated with this system. Firstly, up to a total of twenty ERPC detectors will be assembled as a very compact ring, which provides an adequate angular sampling capability and a relatively high detection efficiency. The detectors are supported on a gantry made of high strength polyamide structure constructed using 3-D printing. This compact system can be directly operated inside an MR scanner. The detector module used in this system offers an intrinsic resolution of 350µm and an excellent energy resolution of around 3~4kev. Each ERPC detector module consists of four pixelated CdTe detectors with a total dimension of 4.5cm×2.25cm. Secondly, a die-cast platinum pinhole inserts and cast lead apertures are developed for this stationary SPECT system. Four 300/500µm diameter pinholes are used for each detector and all pinholes are mounted around a casted cylinder lead aperture tube. The inner diameter of the lead aperture tube is 6cm and the lead tube thickness is 16mm. The opposite detectors are placed 15.6cm apart and the magnification factor of this SPECT system is about 1.2. Thirdly, a comprehensive charge collection model inside strong magnetic field has been developed to account for the magnetic field induced distortion in the SPECT image. This model can accurately predict the detector's energy and spatial response to gamma ray incident events and then help to compensate for the event position recording error due to the strong magnetic field. In this development, we have made an effort to minimize the amount of magnetic materials in the system to alleviate potential interference to magnetic field inhomogeneity.

X-ray Fluorescence Emission Tomography (XFET) with Novel Imaging Geometries - A Monte Carlo Study.

This paper presents a feasibility study for using two new imaging geometries for synchrotron X-ray fluorescence emission tomography (XFET) applications. In the proposed approaches, the object is illuminated with synchrotron X-ray beams of various cross-sectional dimensions. The resultant fluorescence photons are detected by high-resolution imaging-spectrometers coupled to collimation apertures. To verify the performance benefits of the proposed methods over the conventional line-by-line scanning approach, we have used both Monte Carlo simulations and an analytical system performance index to compare several different imaging geometries. This study has demonstrated that the proposed XFET approach could lead to a greatly improved imaging speed, which is critical for making XFET a practical imaging modality for a wide range of applications.

Accelerating X-ray fluorescence computed tomography.

This paper presents new approaches to accelerating X-ray fluorescence tomography (XFCT) that are grounded in both novel image acquisition strategies that improve the quality of the data acquired and in image reconstruction strategies that reduce the amount of data acquired. First, we introduce an alternative imaging scheme that uses an emission tomography (ET) system to collect the fluorescence photons representing an entire 2D slice or volumetric projection of the object at one time. Preliminary results indicate that this could achieve a ten to hundredfold improvement in imaging speed. Secondly, novel image reconstruction algorithms are introduced that allow for improved quantitative accuracy as well as for imaging of regions of interest, which will lead to further reduction in data-acquisition time.

Non-Uniform Object-Space Pixelation (NUOP) for Penalized Maximum-Likelihood Image Reconstruction for a Single Photon Emission Microscope System.

This paper presents a non-uniform object-space pixelation (NUOP) approach for image reconstruction using the penalized maximum likelihood methods. This method was developed for use with a single photon emission microscope (SPEM) system that offers an ultrahigh spatial resolution for a targeted local region inside mouse brain. In this approach, the object-space is divided with non-uniform pixel sizes, which are chosen adaptively based on object-dependent criteria. These include (a) some known characteristics of a target-region, (b) the associated Fisher Information that measures the weighted correlation between the responses of the system to gamma ray emissions occurred at different spatial locations, and (c) the linear distance from a given location to the target-region. In order to quantify the impact of this non-uniform pixelation approach on image quality, we used the Modified Uniform Cramer-Rao bound (MUCRB) to evaluate the local resolution-variance and bias-variance tradeoffs achievable with different pixelation strategies. As demonstrated in this paper, an efficient object-space pixelation could improve the speed of computation by 1-2 orders of magnitude, whilst maintaining an excellent reconstruction for the target-region. This improvement is crucial for making the SPEM system a practical imaging tool for mouse brain studies. The proposed method also allows rapid computation of the first and second order statistics of reconstructed images using analytical approximations, which is the key for the evaluation of several analytical system performance indices for system design and optimization.

Preliminary evaluation of a novel energy-resolved photon-counting gamma ray detector.

In this paper, we present the design and preliminary performance evaluation of a novel energy-resolved photon-counting (ERPC) detector for gamma ray imaging applications. The prototype ERPC detector has an active area of 4.4 cm × 4.4 cm, which is pixelated into 128 × 128 square pixels with a pitch size of 350 µm × 350µm. The current detector consists of multiple detector hybrids, each with a CdTe crystal of 1.1 cm × 2.2 cm × 1 mm, bump-bonded onto a custom-designed application-specific integrated circuit (ASIC). The ERPC ASIC has 2048 readout channels arranged in a 32 × 64 array. Each channel is equipped with pre- and shaping-amplifiers, a discriminator, peak/hold circuitry and an analog-to-digital converter (ADC) for digitizing the signal amplitude. In order to compensate for the pixel-to-pixel variation, two 8-bit digital-to-analog converters (DACs) are implemented into each channel for tuning the gain and offset. The ERPC detector is designed to offer a high spatial resolution, a wide dynamic range of 12-200 keV and a good energy resolution of 3-4 keV. The hybrid detector configuration provides a flexible detection area that can be easily tailored for different imaging applications. The intrinsic performance of a prototype ERPC detector was evaluated with various gamma ray sources, and the results are presented.

An Ultrahigh Resolution SPECT System for I-125 Mouse Brain Imaging Studies.

This paper presents some initial experimental results obtained with a dual-head prototype single photon emission microscope system (SPEM) that is dedicated to mouse brain studies using I-125 labeled radiotracers. In particular, this system will be used for in vivo tacking of radiolabeled T cells in mouse brain. This system is based on the use of the intensified electron multiplying charge-coupled device (I-EMCCD) camera that offers the combination of an excellent intrinsic spatial resolution, a good signal-to-noise ratio, a large active area and a reasonable detection efficiency over an energy range between 27-140keV. In this study, the dual-head SPEM system was evaluated using both resolution phantoms and a mouse with locally injected T cells labelled with I-125. It was demonstrated that for a relatively concentrated source object, the current dual-head SPEM system is capable of visualizing the tiny amount of radioactivity (~12 nCi) carried by a very small number (<1000) of T cells. The current SPEM system design allows four or six camera heads to be installed in a stationary system configuration that offers a doubled or tripled sensitivity at a spatial resolution similar to that obtained with the dualhead system. This development would provide a powerful tool for in vivo and non-invasive tracking of radiolabeled T cells in mouse brain and potentially for other rodent brain imaging studies.

Investigation of the Intrinsic Spatial Resolution of an Intensified EMCCD Scintillation Camera.

In this paper, we present an experimental and Monte Carlo investigation of the intrinsic spatial resolution that can be achieved with the intensified electron-multiplying charge-coupled device (I-EMCCD) gamma camera [1]-[4]. This detector has a very low readout noise, an ultra-high spatial resolution and a large active area of ~ 80 mm diameter, which is well-suited for small animal imaging applications. The intrinsic detector resolutions achieved with different scintillators and under different experimental conditions were compared. In this study, the simple centroiding method was compared with two model-fitting approaches for finding the locations of gamma ray interactions. The results from Monte Carlo simulation have demonstrated that with an appropriate detector configuration, it is possible to achieve an intrinsic resolution of ~ 30 µm FWHM for detecting 27-35 keV gamma rays. The I-EMCCD scintillation camera offers a promising candidate for future ultra-high resolution SPECT imaging applications.

Spectroscopic Performance of Thick HgI2 Detectors.

This paper presents the spectroscopic performance of two newly developed pixelated HgI2 detectors. These detectors are 1 × 1 × 0.814 cm3 and 1 × 1 × 1.016 cm3 in size. Each detector has four closely packed 1 × mm2 anode pixels at the center of one of the 1 × 1 cm2 surfaces. These anode pixels are surrounded by a large anode. All results presented here are based on events from a sub-volume underneath the anode pixels. In these detectors, signals were read out by a discrete electronics based on multiple A-250 pre-amplifiers and a digital oscilloscope for sampling pulse waveforms. Depth sensing technique was used to correct the depth-dependent variation in photopeak amplitude. Main results presented are: (1) energy resolutions of 0.85 ~ 1.3% have been achieved on these detectors; (2) the electron mobility-lifetime product was measured to be ~1 × 10-2 cm2/V and the measured electron lifetime was ~200 µs and (3) variation in electron drifting properties under different anode pixels were observed. Significant non-uniformity in internal electric field strength was also experimentally demonstrated.

An Intensified EMCCD Camera for Low Energy Gamma Ray Imaging Applications.

This paper presents the design and feasibility study of a very-high resolution gamma camera for detecting 27-35 keV X and gamma rays emitted by I-125 labelled radiotracers. This detector consists of a newly developed Electron-multiplying CCD (EMCCD) sensor and a de-magnifier tube coupled to a thin layer of scintillator. A prototype detector was developed and experimentally evaluated. This detector has a detection area of ~ 5 cm2. It provided an intrinsic spatial resolution of < 60 µm FWHM and a high signal-to-noise ratio for detecting the 27-35 keV photons, which ensures an excellent counting efficiency. This detector will be used as the key component for a single photon emission microscope (SPEM) system that is under development.