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Ana Cecilia - One of the best experts on this subject based on the ideXlab platform.

  • charge summing in spectroscopic X Ray Detectors with high z sensors
    2013
    Co-Authors: T Koenig, Marcus Zuber, E Hamann, Ana Cecilia, S Procz, R Ballabriga, Xavier Llopart, Michael Campbell, A Fauler, Tilo Baumbach
    Abstract:

    The spectroscopic performance of photon counting Detectors is limited by the effects of charge sharing between neighboring piXels and the emission of characteristic X-Rays. For these reasons, an event can be either missed or counted more than once. These effects become more and more of a concern when piXel pitches are reduced, and for the technology available so far, this meant that there would always be a trade-off between a high spatial and a high spectral resolution. In this work, we present first measurements obtained with the new MedipiX3RX ASIC, which features a network of charge summing circuits establishing a communication between piXels which helps to mitigate these effects. Combined with cadmium telluride sensors, we show that this new technology is successful at improving a detector's spectroscopic capabilities even at piXel pitches as small as 55 μm. At this pitch, we measure an energy response function similar to that observed for a piXel pitch of 165 μm in the absence of a charge summing circuitry. This amounts to an effective reduction of the piXel area by at least one order of magnitude at a comparable energy response. Additionally, we present synchrotron measurements at high X-Ray fluXes, where significant pulse pile-up occurs, and provide first eXperimental evidence for a net benefit when balancing spectroscopic performance and high fluX tolerance in charge summing mode.

  • imaging properties of small piXel spectroscopic X Ray Detectors based on cadmium telluride sensors
    2012
    Co-Authors: T Koenig, Julia Schulze, Marcus Zuber, Kristian Rink, J S Butzer, E Hamann, Ana Cecilia
    Abstract:

    Spectroscopic X-Ray imaging by means of photon counting Detectors has received growing interest during the past years. Critical to the image quality of such devices is their piXel pitch and the sensor material employed. This paper describes the imaging properties of MedipiX2 MXR multi-chip assemblies bump bonded to 1 mm thick CdTe sensors. Two systems were investigated with piXel pitches of 110 and 165 μm, which are in the order of the mean free path lengths of the characteristic X-Rays produced in their sensors. Peak widths were found to be almost constant across the energy range of 10 to 60 keV, with values of 2.3 and 2.2 keV (FWHM) for the two piXel pitches. The average number of piXels responding to a single incoming photon are about 1.85 and 1.45 at 60 keV, amounting to detective quantum efficiencies of 0.77 and 0.84 at a spatial frequency of zero. Energy selective CT acquisitions are presented, and the two piXel pitches' abilities to discriminate between iodine and gadolinium contrast agents are eXamined. It is shown that the choice of the piXel pitch translates into a minimum contrast agent concentration for which material discrimination is still possible. We finally investigate saturation effects at high X-Ray fluXes and conclude with the finding that higher maXimum count rates come at the cost of a reduced energy resolution.

  • imaging properties of small piXel spectroscopic X Ray Detectors based on cadmium telluride sensors
    2012
    Co-Authors: T Koenig, Julia Schulze, Marcus Zuber, Kristian Rink, J S Butzer, E Hamann, Ana Cecilia
    Abstract:

    Spectroscopic X-Ray imaging by means of photon counting Detectors has received growing interest during the past years. Critical to the image quality of such devices is their piXel pitch and the sensor material employed. This paper describes the imaging properties of MedipiX2 MXR multi-chip assemblies bump bonded to 1 mm thick CdTe sensors. Two systems were investigated with piXel pitches of 110 and 165 μm, which are in the order of the mean free path lengths of the characteristic X-Rays produced in their sensors. Peak widths were found to be almost constant across the energy range of 10 to 60 keV, with values of 2.3 and 2.2 keV (FWHM) for the two piXel pitches. The average number of piXels responding to a single incoming photon are about 1.85 and 1.45 at 60 keV, amounting to detective quantum efficiencies of 0.77 and 0.84 at a spatial frequency of zero. Energy selective CT acquisitions are presented, and the two piXel pitches' abilities to discriminate between iodine and gadolinium contrast agents are eXamined. It is shown that the choice of the piXel pitch translates into a minimum contrast agent concentration for which material discrimination is still possible. We finally investigate saturation effects at high X-Ray fluXes and conclude with the finding that higher maXimum count rates come at the cost of a reduced energy resolution.

T Koenig - One of the best experts on this subject based on the ideXlab platform.

  • charge summing in spectroscopic X Ray Detectors with high z sensors
    2013
    Co-Authors: T Koenig, Marcus Zuber, E Hamann, Ana Cecilia, S Procz, R Ballabriga, Xavier Llopart, Michael Campbell, A Fauler, Tilo Baumbach
    Abstract:

    The spectroscopic performance of photon counting Detectors is limited by the effects of charge sharing between neighboring piXels and the emission of characteristic X-Rays. For these reasons, an event can be either missed or counted more than once. These effects become more and more of a concern when piXel pitches are reduced, and for the technology available so far, this meant that there would always be a trade-off between a high spatial and a high spectral resolution. In this work, we present first measurements obtained with the new MedipiX3RX ASIC, which features a network of charge summing circuits establishing a communication between piXels which helps to mitigate these effects. Combined with cadmium telluride sensors, we show that this new technology is successful at improving a detector's spectroscopic capabilities even at piXel pitches as small as 55 μm. At this pitch, we measure an energy response function similar to that observed for a piXel pitch of 165 μm in the absence of a charge summing circuitry. This amounts to an effective reduction of the piXel area by at least one order of magnitude at a comparable energy response. Additionally, we present synchrotron measurements at high X-Ray fluXes, where significant pulse pile-up occurs, and provide first eXperimental evidence for a net benefit when balancing spectroscopic performance and high fluX tolerance in charge summing mode.

  • imaging properties of small piXel spectroscopic X Ray Detectors based on cadmium telluride sensors
    2012
    Co-Authors: T Koenig, Julia Schulze, Marcus Zuber, Kristian Rink, J S Butzer, E Hamann, Ana Cecilia
    Abstract:

    Spectroscopic X-Ray imaging by means of photon counting Detectors has received growing interest during the past years. Critical to the image quality of such devices is their piXel pitch and the sensor material employed. This paper describes the imaging properties of MedipiX2 MXR multi-chip assemblies bump bonded to 1 mm thick CdTe sensors. Two systems were investigated with piXel pitches of 110 and 165 μm, which are in the order of the mean free path lengths of the characteristic X-Rays produced in their sensors. Peak widths were found to be almost constant across the energy range of 10 to 60 keV, with values of 2.3 and 2.2 keV (FWHM) for the two piXel pitches. The average number of piXels responding to a single incoming photon are about 1.85 and 1.45 at 60 keV, amounting to detective quantum efficiencies of 0.77 and 0.84 at a spatial frequency of zero. Energy selective CT acquisitions are presented, and the two piXel pitches' abilities to discriminate between iodine and gadolinium contrast agents are eXamined. It is shown that the choice of the piXel pitch translates into a minimum contrast agent concentration for which material discrimination is still possible. We finally investigate saturation effects at high X-Ray fluXes and conclude with the finding that higher maXimum count rates come at the cost of a reduced energy resolution.

  • imaging properties of small piXel spectroscopic X Ray Detectors based on cadmium telluride sensors
    2012
    Co-Authors: T Koenig, Julia Schulze, Marcus Zuber, Kristian Rink, J S Butzer, E Hamann, Ana Cecilia
    Abstract:

    Spectroscopic X-Ray imaging by means of photon counting Detectors has received growing interest during the past years. Critical to the image quality of such devices is their piXel pitch and the sensor material employed. This paper describes the imaging properties of MedipiX2 MXR multi-chip assemblies bump bonded to 1 mm thick CdTe sensors. Two systems were investigated with piXel pitches of 110 and 165 μm, which are in the order of the mean free path lengths of the characteristic X-Rays produced in their sensors. Peak widths were found to be almost constant across the energy range of 10 to 60 keV, with values of 2.3 and 2.2 keV (FWHM) for the two piXel pitches. The average number of piXels responding to a single incoming photon are about 1.85 and 1.45 at 60 keV, amounting to detective quantum efficiencies of 0.77 and 0.84 at a spatial frequency of zero. Energy selective CT acquisitions are presented, and the two piXel pitches' abilities to discriminate between iodine and gadolinium contrast agents are eXamined. It is shown that the choice of the piXel pitch translates into a minimum contrast agent concentration for which material discrimination is still possible. We finally investigate saturation effects at high X-Ray fluXes and conclude with the finding that higher maXimum count rates come at the cost of a reduced energy resolution.

Sabee Molloi - One of the best experts on this subject based on the ideXlab platform.

  • th a 217bcd 03 spectral distortion correction for photon counting X Ray Detectors
    2012
    Co-Authors: Huanjun Ding, Sabee Molloi
    Abstract:

    Purpose: To investigate the feasibility of using an image‐based method to correct for spectral distortions from photon‐counting Detectors for their application in breast computed tomography(CT).Methods: The polyenergetic incident spectrum was simulated with the tungstenanode spectral model. EXperiments were performed on a Cadmium‐Zinc‐Telluride (CZT) photon‐counting detector with five energy thresholds. BR12 phantoms of various thicknesses were used for calibration. A non‐linear function was selected to fit the count correlation between the simulated and the measured spectra in the calibration process. To evaluate the proposed spectral distortion correction method, both the corrected counts and the effective attenuation coefficients were compared to the simulated values for polymethyl methacrylate (PMMA) phantoms of 8.7 mm, 48.8 mm and 100.0 mm. The feasibility of applying the proposed method to quantitative material decomposition was tested using a dual‐energy imaging technique with a three‐material phantom that consisted of water, lipid and protein.Results: The implementation of the proposed method reduced the relative RMS error of the output counts in the five energy bins with respect to the simulated incident counts from 23.0%, 33.0% and 54.0% to 1.2%, 1.8% and 7.7% for 8.7 mm, 48.8 mm and 100.0 mm PMMA phantoms, respectively. The accuracy of the effective attenuation coefficient of PMMA estimate was also improved with the proposed spectral distortion correction. Finally, the relative RMS error of water, lipid and protein decompositions in dual‐ energy imaging was significantly reduced from 53.4% to 6.8% after correction was applied. Conclusions: The study demonstrated that the proposed method can effectively reduce the spectral distortions caused by various artifacts, including pulse pileup and charge sharing effects. It may be used as a generalized procedure for the spectrum distortion correction of different photon‐counting Detectors in clinical breast CT systems.

  • image based spectral distortion correction for photon counting X Ray Detectors
    2012
    Co-Authors: Huanjun Ding, Sabee Molloi
    Abstract:

    Purpose: To investigate the feasibility of using an image-based method to correct for distortions induced by various artifacts in the X-Ray spectrum recorded with photon-counting Detectors for their application in breast computed tomography (CT). Methods: The polyenergetic incident spectrum was simulated with the tungsten anode spectral model using the interpolating polynomials (TASMIP) code and carefully calibrated to match the X-Ray tube in this study. EXperiments were performed on a Cadmium-Zinc-Telluride (CZT) photon-counting detector with five energy thresholds. Energy bins were adjusted to evenly distribute the recorded counts above the noise floor. BR12 phantoms of various thicknesses were used for calibration. A nonlinear function was selected to fit the count correlation between the simulated and the measured spectra in the calibration process. To evaluate the proposed spectral distortion correction method, an empirical fitting derived from the calibration process was applied on the raw images recorded for polymethyl methacrylate (PMMA) phantoms of 8.7, 48.8, and 100.0 mm. Both the corrected counts and the effective attenuation coefficient were compared to the simulated values for each of the five energy bins. The feasibility of applying the proposed method to quantitative material decomposition was tested using a dual-energy imaging technique with a three-material phantom that consisted of water, lipid, and protein. The performance of the spectral distortion correction method was quantified using the relative root-mean-square (RMS) error with respect to the eXpected values from simulations or areal analysis of the decomposition phantom. Results: The implementation of the proposed method reduced the relative RMS error of the output counts in the five energy bins with respect to the simulated incident counts from 23.0%, 33.0%, and 54.0% to 1.2%, 1.8%, and 7.7% for 8.7, 48.8, and 100.0 mm PMMA phantoms, respectively. The accuracy of the effective attenuation coefficient of PMMA estimate was also improved with the proposed spectral distortion correction. Finally, the relative RMS error of water, lipid, and protein decompositions in dual-energy imaging was significantly reduced from 53.4% to 6.8% after correction was applied. Conclusions: The study demonstrated that dramatic distortions in the recorded raw image yielded from a photon-counting detector could be eXpected, which presents great challenges for applying the quantitative material decomposition method in spectral CT. The proposed semi-empirical correction method can effectively reduce these errors caused by various artifacts, including pulse pileup and charge sharing effects. Furthermore, rather than detector-specific simulation packages, the method requires a relatively simple calibration process and knowledge about the incident spectrum. Therefore, it may be used as a generalized procedure for the spectral distortion correction of different photon-counting Detectors in clinical breast CT systems.

E Hamann - One of the best experts on this subject based on the ideXlab platform.

  • charge summing in spectroscopic X Ray Detectors with high z sensors
    2013
    Co-Authors: T Koenig, Marcus Zuber, E Hamann, Ana Cecilia, S Procz, R Ballabriga, Xavier Llopart, Michael Campbell, A Fauler, Tilo Baumbach
    Abstract:

    The spectroscopic performance of photon counting Detectors is limited by the effects of charge sharing between neighboring piXels and the emission of characteristic X-Rays. For these reasons, an event can be either missed or counted more than once. These effects become more and more of a concern when piXel pitches are reduced, and for the technology available so far, this meant that there would always be a trade-off between a high spatial and a high spectral resolution. In this work, we present first measurements obtained with the new MedipiX3RX ASIC, which features a network of charge summing circuits establishing a communication between piXels which helps to mitigate these effects. Combined with cadmium telluride sensors, we show that this new technology is successful at improving a detector's spectroscopic capabilities even at piXel pitches as small as 55 μm. At this pitch, we measure an energy response function similar to that observed for a piXel pitch of 165 μm in the absence of a charge summing circuitry. This amounts to an effective reduction of the piXel area by at least one order of magnitude at a comparable energy response. Additionally, we present synchrotron measurements at high X-Ray fluXes, where significant pulse pile-up occurs, and provide first eXperimental evidence for a net benefit when balancing spectroscopic performance and high fluX tolerance in charge summing mode.

  • imaging properties of small piXel spectroscopic X Ray Detectors based on cadmium telluride sensors
    2012
    Co-Authors: T Koenig, Julia Schulze, Marcus Zuber, Kristian Rink, J S Butzer, E Hamann, Ana Cecilia
    Abstract:

    Spectroscopic X-Ray imaging by means of photon counting Detectors has received growing interest during the past years. Critical to the image quality of such devices is their piXel pitch and the sensor material employed. This paper describes the imaging properties of MedipiX2 MXR multi-chip assemblies bump bonded to 1 mm thick CdTe sensors. Two systems were investigated with piXel pitches of 110 and 165 μm, which are in the order of the mean free path lengths of the characteristic X-Rays produced in their sensors. Peak widths were found to be almost constant across the energy range of 10 to 60 keV, with values of 2.3 and 2.2 keV (FWHM) for the two piXel pitches. The average number of piXels responding to a single incoming photon are about 1.85 and 1.45 at 60 keV, amounting to detective quantum efficiencies of 0.77 and 0.84 at a spatial frequency of zero. Energy selective CT acquisitions are presented, and the two piXel pitches' abilities to discriminate between iodine and gadolinium contrast agents are eXamined. It is shown that the choice of the piXel pitch translates into a minimum contrast agent concentration for which material discrimination is still possible. We finally investigate saturation effects at high X-Ray fluXes and conclude with the finding that higher maXimum count rates come at the cost of a reduced energy resolution.

  • imaging properties of small piXel spectroscopic X Ray Detectors based on cadmium telluride sensors
    2012
    Co-Authors: T Koenig, Julia Schulze, Marcus Zuber, Kristian Rink, J S Butzer, E Hamann, Ana Cecilia
    Abstract:

    Spectroscopic X-Ray imaging by means of photon counting Detectors has received growing interest during the past years. Critical to the image quality of such devices is their piXel pitch and the sensor material employed. This paper describes the imaging properties of MedipiX2 MXR multi-chip assemblies bump bonded to 1 mm thick CdTe sensors. Two systems were investigated with piXel pitches of 110 and 165 μm, which are in the order of the mean free path lengths of the characteristic X-Rays produced in their sensors. Peak widths were found to be almost constant across the energy range of 10 to 60 keV, with values of 2.3 and 2.2 keV (FWHM) for the two piXel pitches. The average number of piXels responding to a single incoming photon are about 1.85 and 1.45 at 60 keV, amounting to detective quantum efficiencies of 0.77 and 0.84 at a spatial frequency of zero. Energy selective CT acquisitions are presented, and the two piXel pitches' abilities to discriminate between iodine and gadolinium contrast agents are eXamined. It is shown that the choice of the piXel pitch translates into a minimum contrast agent concentration for which material discrimination is still possible. We finally investigate saturation effects at high X-Ray fluXes and conclude with the finding that higher maXimum count rates come at the cost of a reduced energy resolution.

  • flatfield correction optimization for energy selective X Ray imaging with medipiX3
    2011
    Co-Authors: S Procz, E Hamann, R Ballabriga, A Fauler, M Pichotka, J Lubke, G Blaj, M Campbell, M Mix, A Zwerger
    Abstract:

    PiXelated photon counting semiconductor X-Ray Detectors like the MedipiX feature adjustable energy thresholds allowing selective counting of photons of a specified energy. This development permits for energy selective X-Ray imaging with advanced material information. Furthermore the photon counting function principle of these Detectors allows X-Ray imaging with reduced noise, providing contrast improvement in low contrast objects. The aim of this study is to analyze the behavior of the new MedipiX3 detector, especially regarding flatfield correction for X-Ray imaging applications. First high resolution low contrast X-Ray images and energy selective X-Ray images acquired with the MedipiX3 detector are presented as well in this paper.

Jun Chen - One of the best experts on this subject based on the ideXlab platform.

  • fast response X Ray detector based on nanocrystalline ga2o3 thin film prepared at room temperature
    2021
    Co-Authors: Manni Chen, Zhipeng Zhang, Runze Zhan, Juncong She, Shaozhi Deng, Jun Chen
    Abstract:

    Abstract X-Ray Detectors have broad applications in the fields of medical imaging, security checks, industrial inspections, and scientific research. However, it is still challenging to develop X-Ray Detectors with fast response, high sensitivity, and stable direct conversion. In this study, we fabricated a fast-response X-Ray detector based on a nanocrystalline Ga2O3 thin film, prepared by electron beam evaporation without a high-temperature post-annealing process. The structure characterization results show that Ga2O3 films were nanocrystalline, and a coplanar metal/semiconductor/metal (MSM)-structured X-Ray detector was fabricated. The detection sensitivity reached up to 138.80 μCmGyair−1 cm−3 (at 50 V bias voltage), and the dark current was 50 pA (at 10 V bias voltage). In addition, the rise time and fall time of the transient photocurrent were measured (

  • an aerosol liquid solid process for the general synthesis of halide perovskite thick films for direct conversion X Ray Detectors
    2021
    Co-Authors: Wei Qian, Jun Chen, Jian Wang, Jianwei Chen, Shuang Xiao, Shihe Yang
    Abstract:

    Summary Medical X-Ray computed tomography requires imaging at a low dose rate and in a large area. Halide perovskites have shown high potential for X-Ray detection, but a pressing challenge is the current lack of low-cost methods for large-scale fabrication of high-quality thick perovskite films. Here we demonstrate and elucidate an aerosol-liquid-solid process to enable continuous growth of uniform halide perovskite films at low temperature over a large area of 100 cm2, which are vertically monolithic, and thus beneficial to carrier transport. Direct-conversion X-Ray Detectors based on the representative CsPbI2Br films in conjunction with a deliberated, interface-engineered C-electrode have realized an unprecedented sensitivity (≥1.48 × 105 μC Gyair−1 cm−2) and a low limit of detection (280 nGyair s−1). We have further demonstrated the high-resolution radiographic imaging capability of these films. These results lay the groundwork for large-scale application of halide perovskites in radiation Detectors.

  • an aerosol liquid solid process for the general synthesis of halide perovskite thick films for direct conversion X Ray Detectors
    2020
    Co-Authors: Wei Qian, Jun Chen, Jian Wang, Jianwei Chen, Shuang Xiao, Shihe Yang
    Abstract:

    Medical X-Ray computed tomography requires fast imaging at a low dose rate and in a large area. Halide perovskites have shown high potential for X-Ray detection, but a pressing challenge is the current lack of low-cost methods for large-scale fabrication of high-quality thick perovskite films. Here we demonstrate and elucidate an aerosol-liquid-solid process to enable continuous growth of uniform halide perovskites films at low temperature over a large area of 100 cm2, which are vertically monolithic and monocrystalline, and thus beneficial to carrier transport. Direct conversion X-Ray Detectors based on the representative CsPbI2Br films in conjunction with a deliberated, interface-engineered C-electrode have realized an unprecedented sensitivity (≥1.48×105 μC Gyair−1cm−2). We have further demonstrated the high-resolution radiographic imaging capability of these films. These results lay the groundwork for large scale application of halide perovskites in radiation Detectors.

  • a site cation engineering for highly efficient mapbi3 single crystal X Ray detector
    2019
    Co-Authors: Yanmin Huang, Yuanzhi Jiang, Tingwei He, Mingjian Yuan, Lu Qiao, Run Long, Fan Yang, Jun Chen
    Abstract:

    : Metal halide perovskites have emerged as a new generation of X-Ray detector materials. However, large-sized MAPbI3 single crystals (SCs) still eXhibit lower performance than MAPbBr3 SCs in X-Ray detection. DFT (density functional theory) simulations suggest the problem could be overcome by alloying large-sized cations at the A site. The alloyed process could notably decrease the electron-phonon coupling strength and increase the material defect formation energy. Accordingly, centimeter-sized alloyed DMAMAPbI3 (DMA=dimethylammonium) and GAMAPbI3 (GA=guanidinium) SCs are obtained. Electrical characterizations confirm the GAMAPbI3 SCs display improved charge collection efficiency. It also eXhibits a remarkable reduction of dark current, an important figure of merit for X-Ray Detectors. With a judiciously designed device architecture, the overall detector performance confirms GAMAPbI3 SCs as one of the most sensitive perovskite X-Ray Detectors to date.