Dr. Xu Ji Profile

Dr. Xu Ji

Research Associate at Univ of Wisconsin-Madison

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Author

Publications (21)

Proceedings Article | 4 April 2022 Presentation + Paper

A dagger (†) photon counting detector system for both 2D and 3D interventional imaging

Kevin Treb, Xu Ji, Sarvesh Periyasamy, Mang Feng, Ran Zhang, Dan Bushe, Paul Laeseke, Ke Li

Proceedings Volume 12031, 120310G (2022) https://doi.org/10.1117/12.2612687

KEYWORDS: Imaging systems, Sensors, Spatial resolution, Calcium, Iodine, 3D image processing, Calibration, Photon counting

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Proceedings Article | 4 April 2022 Presentation

A unified artifact correction framework for C-arm photon counting cone beam CT

Mang Feng, Xu Ji, Kevin Treb, Chengzhu Zhang, Emily Cai, Ran Zhang, Sarvesh Periyasamy, Paul Laeseke, Ke Li

Proceedings Volume PC12031, PC120310K (2022) https://doi.org/10.1117/12.2612711

KEYWORDS: Sensors, Photon counting, Signal detection, X-rays, X-ray imaging, X-ray detectors, X-ray computed tomography, Semiconductors, Scattering, Prototyping

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Proceedings Article | 4 April 2022 Presentation + Paper

Enlarging the longitudinal coverage of a prototype C-arm photon counting CT system for image-guided interventions

Kevin Treb, Xu Ji, Mang Feng, Ran Zhang, Sarvesh Periyasamy, Paul Laeseke, Ke Li

Proceedings Volume 12034, 120340Y (2022) https://doi.org/10.1117/12.2612690

KEYWORDS: X-rays, Imaging systems, Prototyping, Collimation, Sensors, X-ray imaging, Spatial resolution, X-ray computed tomography, Visualization, Photon counting

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Existing clinical C-arm interventional x-ray systems equipped with flat panel detectors (FPDs) can generate fluoroscopic, angiographic, and cone-beam CT (CBCT) images with sufficient volumetric coverage for interventional imaging tasks. However, FPD-CBCT does not provide sufficient low-contrast detectability, resolution, or spectral imaging capability desired for certain interventional procedures. To overcome these limitations, a C-arm photon counting detector (PCD) CT prototype was developed by installing an interchangeable strip PCD on the C-arm gantry. The narrow z width of the PCD reduces detector cost and reduces scatter when paired with a narrow beam collimation. However, it does not provide sufficient volumetric coverage compared to the standard FPD. The purpose of this work was to develop a step-and-shoot data acquisition method to enlarge the effective z-coverage of the C-arm strip PCD-CT system. A total of 10 back-and-forth short-scan C-arm gantry rotations were used with image object translation. By using an Arduino board to process the x-ray-on pulse signals in real-time, a motorized patient table prototype was synchronized with the C-arm system such that it translates the object by the PCD width during the rest time in between gantry rotations. To evaluate whether this multisweep step-and-shoot acquisition mode can generate high-quality and volumetric PCD-CT images, experiments were performed using an anthropomorphic head phantom, and a stent. The multi-sweep step-and-shoot C-arm protocol resulted in volumetric PCD-CT images with lower image noise and improved low-contrast visualization over the FPD-CBCT in the head phantom, as well as improved visibility of small iodinated blood vessels using maximum intensity projections. Under an ultra-high-resolution PCD mode, the fine structures of the stent were visualized more clearly by the PCD-CT than the highest-available resolution provided by the FPD-CBCT. The multi-sweep step-and-shoot acquisition can therefore extend the z-coverage of the C-arm PCD-CT prototype by a factor of 10 to enable high-quality and volumetric C-arm PCD-CT images acquired with a narrow beam-narrow detector setup for image-guided interventions.

Proceedings Article | 21 March 2022 Presentation

A multi-contrast chest x-ray radiography prototype with low-dose fast scanning-beam acquisition

Daniel Bushe, Xu Ji, Ran Zhang, Mang Feng, Kevin Treb, Guang-Hong Chen, Ke Li

Proceedings Volume PC12031, PC1203103 (2022) https://doi.org/10.1117/12.2612676

KEYWORDS: Chest imaging, Radiography, Imaging systems, Prototyping, Pulmonary disorders, Chronic obstructive pulmonary disease, X-rays, X-ray imaging, Standards development, Sensors

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Proceedings Article | 15 February 2021 Presentation

Model-based inter- and intra-panel inconsistency correction for photon counting detector CT

Mang Feng, Xu Ji, Ran Zhang, Ke Li

Proceedings Volume 11595, 115951V (2021) https://doi.org/10.1117/12.2580817

KEYWORDS: Sensors, Photon counting, Computed tomography, Model-based design, Systems modeling, Aluminum, Semiconductors, Image quality, Head, Data analysis

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Proceedings Article | 15 February 2021 Presentation

Single-kV multi-contrast x-ray imaging for gout detection and gout-pseudogout differentiation

Daniel Bushe, Ran Zhang, Xu Ji, Mang Feng, Guang-Hong Chen, Ke Li

Proceedings Volume 11595, 115951P (2021) https://doi.org/10.1117/12.2580972

KEYWORDS: X-ray imaging, Crystals, Imaging systems, Diagnostics, Crystallography, X-rays, Signal detection, Signal attenuation, Numerical simulations, Calcium

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Proceedings Article | 15 February 2021 Presentation

Anomalous edge response of photon counting detectors induced by pulse pileup and anti-coincidence logic

Xu Ji, Ran Zhang, Ke Li

Proceedings Volume 11595, 115950F (2021) https://doi.org/10.1117/12.2581086

KEYWORDS: Sensors, Photon counting, Logic, Tungsten, Time correlated photon counting, Spatial resolution, Photodetectors

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Proceedings Article | 15 February 2021 Presentation

Photon counting CT in a C-arm interventional system: hardware development and artifact corrections

Xu Ji, Mang Feng, Ran Zhang, Guang-Hong Chen, Ke Li

Proceedings Volume 11595, 115950A (2021) https://doi.org/10.1117/12.2581087

KEYWORDS: Photon counting, Sensors, Calibration, Computed tomography, Imaging systems, Spatial resolution, Quantum efficiency, Model-based design, Head, Distortion

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Proceedings Article | 15 February 2021 Presentation + Paper

A hybrid photon counting and flat panel detector system for periprocedural hemorrhage monitoring in the angio suite

Kevin Treb, Xu Ji, Mang Feng, Ran Zhang, Sebastian Schafer, Ke Li

Proceedings Volume 11595, 115950U (2021) https://doi.org/10.1117/12.2581242

KEYWORDS: Sensors, Imaging systems, Photon counting, Computed tomography, Imaging spectroscopy, Spectroscopy, Scanners, Reliability, Photodetectors, Iodine

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Endovascular procedures performed in the angio suite have gained considerable popularity for treatment of ischemic stroke as well as aneurysms. However, new intracranial hemorrhage (ICH) may develop during these procedures, and it is highly desirable to arm the angio suite with real-time and reliable ICH monitoring tools. Currently, angio suites are equipped with scintillator-based flat panel detector (FPD) imaging systems for both planar and cone beam CT (CBCT) imaging applications. However, the reliability of CBCT for ICH imaging is insufficient due to its poor low-contrast detectability compared with MDCT and lack of spectral imaging capability for differentiating between ICH, calcifications, and iodine staining from periprocedural contrast-enhanced imaging sequences. To preserve the benefits of the FPD for 2D imaging and certain high-contrast 3D imaging tasks while adding a high quality, quantitative, and affordable CT imaging capability to the angio room for intraoperative ICH monitoring, a hybrid detector system was developed that includes the existing FPD on the C-arm gantry and a strip photon-counting detector (PCD) that can be translated into the field-of-view for high quality PCD-CT imaging at a given brain section-of-interest. The hybrid system maintains the openness and ease of use of the C-arm system without the need to remodel the angio room and without installing a slidinggantry MDCT (aka Angio CT) with orders of magnitude higher costs. Additionally, the cost of the strip PCD is much less than the cost of a large-area PCD. To demonstrate the feasibility and potential benefits of the hybrid PCD-FPD system, a series of physical phantom studies, and human cadaver studies were performed at a gantry rotation speed (7 s) and radiation dose level that closely match those of clinical CBCT acquisitions. The experimental images of C-arm PCD-CT demonstrated MDCT-equivalent low-contrast detectability of PCD-CT and significantly reduced artifacts compared with FPD-based CBCT.

Proceedings Article | 16 March 2020 Presentation

Impacts of pulse pileup, charge sharing, and anti-charge sharing on the noise power spectra of photon counting detectors: theoretical analysis and experimental demonstrations (Conference Presentation)

Ke Li, Xu Ji, Ran Zhang

Proceedings Volume 11312, 1131213 (2020) https://doi.org/10.1117/12.2549784

KEYWORDS: Photon counting, Sensors, Monte Carlo methods, Device simulation

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Proceedings Article | 16 March 2020 Paper

Phase contrast CT enabled three-material decomposition in spectral CT imaging

Xu Ji, Ran Zhang, Ke Li, Guang-Hong Chen

Proceedings Volume 11312, 113121B (2020) https://doi.org/10.1117/12.2549014

KEYWORDS: X-ray computed tomography, Phase contrast, Dual energy imaging, X-rays, Computed tomography, Absorption

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Proceedings Article | 16 March 2020 Presentation + Paper

Impact of photon counting detector spectral distortion on virtual non-contrast CT imaging

Mang Feng, Xu Ji, Ran Zhang, Jessica Miller, Guang-Hong Chen, Ke Li

Proceedings Volume 11312, 113121J (2020) https://doi.org/10.1117/12.2549737

KEYWORDS: X-ray computed tomography, Distortion, Iodine, Photon counting, Sensors, Calcium, Computed tomography, X-rays, Signal attenuation, Blood

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Proceedings Article | 7 March 2019 Presentation + Paper

Spectrum optimization in photon counting detector based iodine K-edge CT imaging

Mang Feng, Xu Ji, Kevin Treb, Ran Zhang, Guang-Hong Chen, Ke Li

Proceedings Volume 10948, 109481C (2019) https://doi.org/10.1117/12.2512893

KEYWORDS: Iodine, X-ray computed tomography, X-rays, X-ray imaging, Photon counting

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Proceedings Article | 1 March 2019 Presentation + Paper

An experimental method to correct drift-induced error in zero-frequency DQE measurement

Xu Ji, Mang Feng, Ran Zhang, Guang-Hong Chen, Ke Li

Proceedings Volume 10948, 109480H (2019) https://doi.org/10.1117/12.2512467

KEYWORDS: Signal to noise ratio, Imaging systems, Error analysis, Modulation transfer functions, Signal detection, Photons, Numerical simulations, X-ray imaging

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Proceedings Article | 1 March 2019 Presentation + Paper

Impacts of photon counting detector to cerebral CT angiography maximum intensity projection (MIP) images

Evan Harvey, Mang Feng, Xu Ji, Ran Zhang, Guang-Hong Chen, Ke Li

Proceedings Volume 10948, 109481Z (2019) https://doi.org/10.1117/12.2513205

KEYWORDS: Signal to noise ratio, Computed tomography, Arteries, Sensors, Photon counting, Angiography, Signal detection, X-ray computed tomography, Spatial resolution, Head

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Cerebral CT angiography (CTA) is widely used for the diagnosis of various cerebrovascular diseases, including strokes, vasculitis, aneurysms, and etc.2–4 For the diagnosis of ischemic strokes, the availability of high quality CTA images not only helps in identifying the presence/location of large vessel occlusion but also facilitates the assessment of collateral blood supply. As another example, accurate rendering of the superficial temporal arteries is valuable in identifying vessel inflammations induced by giant cell arteritis.5 While CTA is an established clinical gold standard for imaging large cerebral arteries and veins,1 an important challenge that currently remains for MDCT-based CTA is its limited performance in imaging small perforating arteries with a diameter below 0.5 mm.4 As a consequence, the relativley invasive artery biopsy procedure remains the current clinical gold standard for the diagnosis of giant cell arteritis.6 The use of indirect conversion energy integrating detectors puts intrinsic limit on the spatial resolution of MDCT, both in-plane and along the z direction. Severe partial volume averaging effect (PVE) and the preferential weighting of high energy photons7 are among major reasons for the relatively poor performance of MDCT-based CTA for imaging iodinated small vessels. Photon counting detector-based CT (PCD-CT) offers potential technological solutions to these challenges MDCT systems face for CTA. When compared to MDCT, the direct conversion design of PCD reduces limitations on both in-plane and through-plane spatial resolution, and the inherent equal weighting of high and low energy photons of PCD-CT systems offers an improvement in the CNR of iodinated vessels. The purpose of this work was to theoretically and experimentally study the potential impacts of the PCD-CT technology to an important component of CTA image package: the maximum intensity projection (MIP) image. MIP is a simple 3D image visualization method to display CTA data sets. Based on source images alone, it can be very challenging to evaluate occlusion conditions since most vessels extend to different z positions. In comparison, a MIP image that extracted information from a much longer z range can provide clearer evidence for an occlusion; in addition, it can effectively enhance the visibility of small collateral vessels. This work first derived the statistical properties of the MIP image, then analyzed how each of the benefits of PCD (improved z resolution; reduced noise autocovariance along z) propagates from the source CT images to the final MIP image. Finally, experiments were performed using a benchtop PCD-CT system and an anthropomorphic CTA phantom to showcase the significantly improved visibility of small perforating arteries.

Proceedings Article | 1 March 2019 Presentation + Paper

Impact of the sensitivity factor on the signal-to-noise ratio in grating-based phase contrast imaging

Xu Ji, Ran Zhang, Ke Li, Guang-Hong Chen

Proceedings Volume 10948, 109481Q (2019) https://doi.org/10.1117/12.2512251

KEYWORDS: Signal to noise ratio, Statistical analysis, Phase contrast, Photons, Numerical simulations, Refraction, Phase shifts, Visibility, X-rays

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Proceedings Article | 9 March 2018 Paper

Task-driven optimization of an experimental photon counting detector CT system for intracranial hemorrhage detection

Xu Ji, Ran Zhang, Guang-Hong Chen, Ke Li

Proceedings Volume 10573, 105731P (2018) https://doi.org/10.1117/12.2293942

KEYWORDS: Sensors, Head, Imaging systems, Photon counting, X-ray computed tomography, Apodization, Modulation transfer functions, Computed tomography, Performance modeling, X-rays

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Proceedings Article | 9 March 2018 Presentation + Paper

Design, construction, and initial results of a prototype multi-contrast x-ray breast imaging system

Ke Li, Ran Zhang, John Garrett, Yongshuai Ge, Xu Ji, Guang-Hong Chen

Proceedings Volume 10573, 105730W (2018) https://doi.org/10.1117/12.2293921

KEYWORDS: Imaging systems, X-ray imaging, Prototyping, X-rays, Breast imaging, Diffraction gratings, Interferometers

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Proceedings Article | 9 March 2017 Presentation + Paper

Signal and noise characteristics of a CdTe-based photon counting detector: cascaded systems analysis and experimental studies

Xu Ji, Ran Zhang, Yongshuai Ge, Guang-Hong Chen, Ke Li

Proceedings Volume 10132, 1013207 (2017) https://doi.org/10.1117/12.2255063

KEYWORDS: Photon counting, Sensors, Image processing, Interference (communication), X-rays, Modulation transfer functions, Signal detection, Cadmium, Systems modeling, X-ray imaging, Medical imaging, Single photon, X-ray detectors

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Proceedings Article | 9 March 2017 Paper

Weighted singular value decomposition (wSVD) to improve the radiation dose efficiency of grating-based x-ray phase contrast imaging with a photon counting detector

Xu Ji, Yongshuai Ge, Ran Zhang, Ke Li, Guang-Hong Chen

Proceedings Volume 10132, 101325I (2017) https://doi.org/10.1117/12.2255014

KEYWORDS: Imaging systems, Signal to noise ratio, Phase contrast, Denoising, Interference (communication), Interferometers, Photon counting, Sensors, Visibility, X-ray detectors, X-ray imaging, X-rays

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Proceedings Article | 9 March 2017 Presentation + Paper

Potential bias in signal estimation for grating-based x-ray multi-contrast imaging

Xu Ji, Yongshuai Ge, Ran Zhang, Ke Li, Guang-Hong Chen

Proceedings Volume 10132, 1013219 (2017) https://doi.org/10.1117/12.2254429

KEYWORDS: Signal detection, X-ray detectors, X-ray imaging, X-rays, Phase contrast, Absorption, Data acquisition, Visibility, Sensors, Photon counting, Numerical simulations, Phase measurement, Interferometers, Statistical analysis, Photons

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Showing 5 of 21 publications

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