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Miao H, Williams JC, Josell D. A four-grating interferometer for x-ray multi-contrast imaging. Med Phys 2024; 51:3648-3657. [PMID: 38558430 DOI: 10.1002/mp.17052] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2023] [Revised: 02/08/2024] [Accepted: 03/24/2024] [Indexed: 04/04/2024] Open
Abstract
BACKGROUND X-ray multi-contrast imaging with gratings provides a practical method to detect differential phase and dark-field contrast images in addition to the x-ray absorption image traditionally obtained in laboratory or hospital environments. Systems have been developed for preclinical applications in areas including breast imaging, lung imaging, rheumatoid arthritis hand imaging and kidney stone imaging. PURPOSE Prevailing x-ray interferometers for multi-contrast imaging include Talbot-Lau interferometers and universal moiré effect-based phase-grating interferometers. Talbot-Lau interferometers suffer from conflict between high interferometer sensitivity and large field of view (FOV) of the object being imaged. A small period analyzer grating is necessary to simultaneously achieve high sensitivity and large FOV within a compact imaging system but is technically challenging to produce for high x-ray energies. Phase-grating interferometers suffer from an intrinsic fringe period ranging from a few micrometers to several hundred micrometers that can hardly be resolved by large area flat panel x-ray detectors. The purpose of this work is to introduce a four-grating x-ray interferometer that simultaneously allows high sensitivity and large FOV, without the need for a small period analyzer grating. METHODS The four-grating interferometer consists of a source grating placed downstream of and close to the x-ray source, a pair of phase gratings separated by a fixed distance placed downstream of the source grating, and an analyzer grating placed upstream of and close to the x-ray detector. The object to be imaged is placed upstream of and close to the phase-grating pair. The distance between the source grating and the phase-grating pair is designed to be far larger than that between the phase-grating pair and the analyzer grating to promote simultaneously high sensitivity and large FOV. The method was evaluated by constructing a four-grating interferometer with an 8 µm period source grating, a pair of phase gratings of 2.4 µm period, and an 8 µm period analyzer grating. RESULTS The fringe visibility of the four-grating interferometer was measured to be ≈24% at 40 kV and ≈18% at 50 kV x-ray tube operating voltage. A quartz bead of 6 mm diameter was imaged to compare the theoretical and experimental phase contrast signal with good agreement. Kidney stone specimens were imaged to demonstrate the potential of such a system for classification of kidney stones. CONCLUSIONS The proposed four-grating interferometer geometry enables a compact x-ray multi-contrast imaging system with simultaneously high sensitivity and large FOV. Relaxation of the requirement for a small period analyzer grating makes it particularly suitable for high x-ray energy applications such as abdomen and chest imaging.
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Affiliation(s)
- Houxun Miao
- General Optics, LLC, Zionsville, Indiana, USA
| | - James C Williams
- Department of Anatomy, Cell Biology & Physiology, Indiana University School of Medicine, Indianapolis, Indiana, USA
| | - Daniel Josell
- Materials Science and Engineering Division, National Institute of Standards and Technology, Gaithersburg, Maryland, USA
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Cai X, Tan Y, Zhang X, Yang J, Xu J, Zheng H, Liang D, Ge Y. Energy resolving dark-field imaging with dual phase grating interferometer. OPTICS EXPRESS 2023; 31:44273-44282. [PMID: 38178502 DOI: 10.1364/oe.503843] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/21/2023] [Accepted: 11/14/2023] [Indexed: 01/06/2024]
Abstract
X-ray dark-filed imaging is a powerful approach to quantify the dimension of micro-structures of the object. Often, a series of dark-filed signals have to be measured under various correlation lengths. For instance, this is often achieved by adjusting the sample positions by multiple times in Talbot-Lau interferometer. Moreover, such multiple measurements can also be collected via adjustments of the inter-space between the phase gratings in dual phase grating interferometer. In this study, the energy resolving capability of the dual phase grating interferometer is explored with the aim to accelerate the data acquisition speed of dark-filed imaging. To do so, both theoretical analyses and numerical simulations are investigated. Specifically, the responses of the dual phase grating interferometer at varied X-ray beam energies are studied. Compared with the mechanical position translation approach, the combination of such energy resolving capability helps to greatly shorten the total dark-field imaging time in dual phase grating interferometer.
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Olivo A. Edge-illumination x-ray phase-contrast imaging. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2021; 33:363002. [PMID: 34167096 PMCID: PMC8276004 DOI: 10.1088/1361-648x/ac0e6e] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/01/2021] [Revised: 06/07/2021] [Accepted: 06/24/2021] [Indexed: 05/08/2023]
Abstract
Although early demonstration dates back to the mid-sixties, x-ray phase-contrast imaging (XPCI) became hugely popular in the mid-90s, thanks to the advent of 3rd generation synchrotron facilities. Its ability to reveal object features that had so far been considered invisible to x-rays immediately suggested great potential for applications across the life and the physical sciences, and an increasing number of groups worldwide started experimenting with it. At that time, it looked like a synchrotron facility was strictly necessary to perform XPCI with some degree of efficiency-the only alternative being micro-focal sources, the limited flux of which imposed excessively long exposure times. However, new approaches emerged in the mid-00s that overcame this limitation, and allowed XPCI implementations with conventional, non-micro-focal x-ray sources. One of these approaches showing particular promise for 'real-world' applications is edge-illumination XPCI: this article describes the key steps in its evolution in the context of contemporary developments in XPCI research, and presents its current state-of-the-art, especially in terms of transition towards practical applications.
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Affiliation(s)
- Alessandro Olivo
- Department of Medical Physics and Biomedical Engineering, UCL, London, United Kingdom
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Birnbacher L, Braig EM, Pfeiffer D, Pfeiffer F, Herzen J. Quantitative X-ray phase contrast computed tomography with grating interferometry : Biomedical applications of quantitative X-ray grating-based phase contrast computed tomography. Eur J Nucl Med Mol Imaging 2021; 48:4171-4188. [PMID: 33846846 PMCID: PMC8566444 DOI: 10.1007/s00259-021-05259-6] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2020] [Accepted: 02/11/2021] [Indexed: 11/25/2022]
Abstract
The ability of biomedical imaging data to be of quantitative nature is getting increasingly important with the ongoing developments in data science. In contrast to conventional attenuation-based X-ray imaging, grating-based phase contrast computed tomography (GBPC-CT) is a phase contrast micro-CT imaging technique that can provide high soft tissue contrast at high spatial resolution. While there is a variety of different phase contrast imaging techniques, GBPC-CT can be applied with laboratory X-ray sources and enables quantitative determination of electron density and effective atomic number. In this review article, we present quantitative GBPC-CT with the focus on biomedical applications.
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Affiliation(s)
- Lorenz Birnbacher
- Physics Department, Munich School of Bioengineering, Technical University of Munich, Munich, Germany
- Department of Diagnostic and Interventional Radiology, School of Medicine, Klinikum rechts der Isar, Technical University of Munich, Munich, Germany
| | - Eva-Maria Braig
- Physics Department, Munich School of Bioengineering, Technical University of Munich, Munich, Germany
| | - Daniela Pfeiffer
- Department of Diagnostic and Interventional Radiology, School of Medicine, Klinikum rechts der Isar, Technical University of Munich, Munich, Germany
| | - Franz Pfeiffer
- Physics Department, Munich School of Bioengineering, Technical University of Munich, Munich, Germany
- Department of Diagnostic and Interventional Radiology, School of Medicine, Klinikum rechts der Isar, Technical University of Munich, Munich, Germany
| | - Julia Herzen
- Physics Department, Munich School of Bioengineering, Technical University of Munich, Munich, Germany.
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5
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Ji X, Zhang R, Li K, Chen GH. Dual Energy Differential Phase Contrast CT (DE-DPC-CT) Imaging. IEEE TRANSACTIONS ON MEDICAL IMAGING 2020; 39:3278-3289. [PMID: 32340940 PMCID: PMC7584735 DOI: 10.1109/tmi.2020.2990347] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
When more than two elemental materials are present in a given object, material quantification may not be robust and accurate when the routine two-material decomposition scheme in current dual energy CT imaging is employed. In this work, we present an innovative scheme to accomplish accurate three-material decomposition with measurements from a dual energy differential phase contrast CT (DE-DPC-CT) acquisition. A DE-DPC-CT system was constructed using a grating interferometer and a photon counting CT imaging system with two energy bins. The DE-DPC-CT system can simultaneously measure both the imaginary and the real part of the complex refractive index to enable a three-material decomposition. Physical phantom with 21 material inserts were constructed and measured using DE-DPC-CT system. Results demonstrated excellent accuracy in elemental material quantification. For example, relative root-mean-square errors of 4.5% for calcium and 5.2% for iodine were achieved using the proposed three-material decomposition scheme. Biological tissues with iodine inserts were used to demonstrate the potential utility of the proposed spectral CT imaging method. Experimental results showed that the proposed method correctly differentiates the bony structure, iodine, and the soft tissue in the biological specimen samples. A triple spectra CT scan was also performed to benchmark the performance of the DE-DPC-CT scan. Results demonstrated that the material decomposition from the DE-DPC-CT has a much lower quantification noise than that from the triple spectra CT scan.
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Ge Y, Liu P, Ni Y, Chen J, Yang J, Su T, Zhang H, Guo J, Zheng H, Li Z, Liang D. Enhancing the X-Ray Differential Phase Contrast Image Quality With Deep Learning Technique. IEEE Trans Biomed Eng 2020; 68:1751-1758. [PMID: 32746069 DOI: 10.1109/tbme.2020.3011119] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
OBJECTIVE The purpose of this work is to investigate the feasibility of using deep convolutional neural network (CNN) to improve the image quality of a grating-based X-ray differential phase contrast imaging (XPCI) system. METHODS In this work, a novel deep CNN based phase signal extraction and image noise suppression algorithm (named as XP-NET) is developed. The numerical phase phantom, the ex vivo biological specimen and the ACR breast phantom are evaluated via the numerical simulations and experimental studies, separately. Moreover, images are also evaluated under different low radiation levels to verify its dose reduction capability. RESULTS Compared with the conventional analytical method, the novel XP-NET algorithm is able to reduce the bias of large DPC signals and hence increasing the DPC signal accuracy by more than 15%. Additionally, the XP-NET is able to reduce DPC image noise by about 50% for low dose DPC imaging tasks. CONCLUSION This proposed novel end-to-end supervised XP-NET has a great potential to improve the DPC signal accuracy, reduce image noise, and preserve object details. SIGNIFICANCE We demonstrate that the deep CNN technique provides a promising approach to improve the grating-based XPCI performance and its dose efficiency in future biomedical applications.
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Ge Y, Chen J, Zhu P, Yang J, Deng S, Shi W, Zhang K, Guo J, Zhang H, Zheng H, Liang D. Dual phase grating based X-ray differential phase contrast imaging with source grating: theory and validation. OPTICS EXPRESS 2020; 28:9786-9801. [PMID: 32225579 DOI: 10.1364/oe.381759] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/05/2019] [Accepted: 01/12/2020] [Indexed: 06/10/2023]
Abstract
In this work, we developed a new theoretical framework using wave optics to explain the working mechanism of the grating based X-ray differential phase contrast imaging (XPCI) interferometer systems consist of more than one phase grating. Under the optical reversibility principle, the wave optics interpretation was simplified into the geometrical optics interpretation, in which the phase grating was treated as a thin lens. Moreover, it was derived that the period of an arrayed source, e.g., the period of a source grating, is always equal to the period of the diffraction fringe formed on the source plane. When a source grating is utilized, the theory indicated that it is better to keep the periods of the two phase gratings different to generate large period diffraction fringes. Experiments were performed to validate these theoretical findings.
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Abstract
Under the JST-ERATO project in progress to develop X-ray and neutron phase-imaging methods together, recent achievements have been selected and reviewed after describing the merit and the principle of the phase imaging method. For X-ray phase imaging, recent developments of four-dimensional phase tomography and phase microscopy at SPring-8, Japan are mainly presented. For neutron phase imaging, an approach in combination with the time-of-flight method developed at J-PARC, Japan is described with the description of new Gd grating fabrication.
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Ji X, Zhang R, Li K, Chen GH. Is high sensitivity always desirable for a grating-based differential phase contrast imaging system? Med Phys 2019; 47:1215-1228. [PMID: 31872886 DOI: 10.1002/mp.13984] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2019] [Revised: 12/10/2019] [Accepted: 12/10/2019] [Indexed: 11/08/2022] Open
Abstract
PURPOSE In grating-based x-ray differential phase contrast (DPC) imaging, the measured signal amplitude of the phase shift induced by an image object is proportional to the so-called system sensitivity. Therefore, to achieve a better signal-to-noise (SNR) for improved imaging performance, it is generally believed that one should increase the system sensitivity by reducing the period of the analyzer grating or increasing the distance between the phase grating and analyzer grating. The purpose of this work is to theoretically and experimentally demonstrate that there is an optimal system sensitivity to attain the highest SNR for a given task provided that the standard phase-stepping acquisition and phase retrieval methods are used. When system sensitivity goes beyond this optimal value, SNR decreases and the imaging performance deteriorates. METHODS Due to the fundamental fact that the measured phase signal is a cyclic variable, the phase wrapping effect is inevitable in DPC imaging when the system sensitivity increases. The phase wrapping effect appears in both signal and noise measurements. The effect in the signal measurement is manifested in the so-called signal statistical bias and such effect often impacts the accuracy of the measurement. The phase wrapping effect also appears in the noise variance measurement and impacts the precision of the measurement. A thorough theoretical analysis was performed in this work to demonstrate the quantitative impacts of phase wrapping on both signal bias and noise variance and thus on the actual system SNR. The joint effect of phase wrapping in both the signal bias and noise variance yields an optimal system sensitivity to achieve the highest SNR. Both extensive numerical simulation studies and experimental studies were performed to validate the theoretical analysis. RESULTS Both theoretical analysis and experimental studies show that the SNR of the DPC signal is not always proportional to the sensitivity due to the cyclic nature of the signal and the phase wrapping effect. For a given refraction angle and exposure level, there exists an optimal sensitivity factor that maximizes the SNR, beyond which, increasing the sensitivity will decrease the SNR. CONCLUSIONS Increase of system sensitivity does not always improve x-ray DPC imaging performance provided that the standard phase-stepping acquisition and phase retrieval methods are used.
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Affiliation(s)
- Xu Ji
- Department of Medical Physics, University of Wisconsin School of Medicine and Public Health, Madison, WI, 53705, USA
| | - Ran Zhang
- Department of Medical Physics, University of Wisconsin School of Medicine and Public Health, Madison, WI, 53705, USA
| | - Ke Li
- Department of Medical Physics, University of Wisconsin School of Medicine and Public Health, Madison, WI, 53705, USA.,Department of Radiology, University of Wisconsin School of Medicine and Public Health, Madison, WI, 53705, USA
| | - Guang-Hong Chen
- Department of Medical Physics, University of Wisconsin School of Medicine and Public Health, Madison, WI, 53705, USA.,Department of Radiology, University of Wisconsin School of Medicine and Public Health, Madison, WI, 53705, USA
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10
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Sharma R, Sharma SD, Sarkar PS, Singh B, Agrawal AK, Datta D. Phantom-Based Feasibility Studies on Phase-Contrast Mammography at Indian Synchrotron Facility Indus-2. J Med Phys 2019; 44:39-48. [PMID: 30983770 PMCID: PMC6438051 DOI: 10.4103/jmp.jmp_98_18] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Introduction: Use of synchrotron radiation (SR) X-ray source in medical imaging has shown great potential for improving soft-tissue image contrast such as the breast. The present study demonstrates quantitative X-ray phase-contrast imaging (XPCI) technique derived from propagation-dependent phase change observed in the breast tissue-equivalent test materials. Materials and Methods: Indian synchrotron facility (Indus-2, Raja Ramanna Centre of Advanced Technology [RRCAT]) was used to carry out phantom feasibility study on phase-contrast mammography. Different phantoms and samples, including locally fabricated breast tissue-equivalent phantoms were used to perform absorption and phase mode imaging using 12 and 16 keV SR X-ray beam. Edge-enhancement index (EEI) and edge enhancement to noise ratio (EE/N) were measured for all the images. Absorbed dose to air values were calculated for 12 and 16 keV SR X-ray beam using the measured SR X-ray photon flux at the object plane and by applying the standard radiation dosimetry formalism. Results and Conclusion: It was observed in case of all the phantoms and test samples that EEI and EE/N values are relatively higher for images taken in the phase mode. The absorbed dose to air at imaging plane was found to be 75.59 mGy and 28.9 mGy for 12 and 16 keV SR energies, respectively. However, these dose values can be optimized by reducing the image acquisition time without compromising the image quality when clinical samples are imaged. This work demonstrates the feasibility of XPCI in mammography using 12 and 16 keV SR X-ray beams.
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Affiliation(s)
- Reena Sharma
- Division of Radiological Physics and Advisory, Bhabha Atomic Research Centre, CT and CRS, Mumbai, Maharashtra, India.,Department of Atomic Energy, Homi Bhabha National Institute, Mumbai, Maharashtra, India
| | - S D Sharma
- Division of Radiological Physics and Advisory, Bhabha Atomic Research Centre, CT and CRS, Mumbai, Maharashtra, India.,Department of Atomic Energy, Homi Bhabha National Institute, Mumbai, Maharashtra, India
| | - P S Sarkar
- Department of Atomic Energy, Homi Bhabha National Institute, Mumbai, Maharashtra, India.,Division of Technical Physics, Bhabha Atomic Research Centre, Trombay, Mumbai, Maharashtra, India
| | - B Singh
- Division of Technical Physics, Bhabha Atomic Research Centre, Trombay, Mumbai, Maharashtra, India
| | - A K Agrawal
- Division of Technical Physics, Bhabha Atomic Research Centre, Trombay, Mumbai, Maharashtra, India
| | - D Datta
- Division of Radiological Physics and Advisory, Bhabha Atomic Research Centre, CT and CRS, Mumbai, Maharashtra, India.,Department of Atomic Energy, Homi Bhabha National Institute, Mumbai, Maharashtra, India
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Ji X, Zhang R, Li K, Chen GH. Impact of the sensitivity factor on the signal-to-noise ratio in grating-based phase contrast imaging. PROCEEDINGS OF SPIE--THE INTERNATIONAL SOCIETY FOR OPTICAL ENGINEERING 2019; 10948:109481Q. [PMID: 31068738 PMCID: PMC6502255 DOI: 10.1117/12.2512251] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
The sensitivity factor of a grating-based x-ray differential phase contrast (DPC) imaging system determines how much fringe shift can be observed for a given refraction angle. It is commonly believed that increasing the sensitivity factor will improve the signal-to-noise ratio (SNR) of the phase signal. However, this may not always be the case if the intrinsic phase wrapping effect is taken into consideration. In this work, a theoretical derivation is provided to quantify relationship between the sensitivity and SNR for a given refraction angle, exposure level, and grating based x-ray DPC system. The theoretical derivation shows that the expected phase signal is not always proportional to the sensitivity factor and may even decrease when the sensitivity factor becomes too large. The noise variance of the signal is not always solely dependent on the exposure level and fringe visibility but may become signal-dependent under certain circumstances. As a result, SNR of the phase signal does not always increase with higher sensitivity. Numerical simulation studies were performed to validate the theoretical models. Results show that when the fringe visibility and exposure level are fixed, there exists an optimal sensitivity factor which maximizes the SNR for a given refraction angle; further increase of the sensitivity factor may decrease the SNR.
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Affiliation(s)
- Xu Ji
- Department of Medical Physics, University of Wisconsin School of Medicine and Public Health, Madison, WI
| | - Ran Zhang
- Department of Medical Physics, University of Wisconsin School of Medicine and Public Health, Madison, WI
| | - Ke Li
- Department of Medical Physics, University of Wisconsin School of Medicine and Public Health, Madison, WI
- Department of Radiology, University of Wisconsin School of Medicine and Public Health, Madison, WI
| | - Guang-Hong Chen
- Department of Medical Physics, University of Wisconsin School of Medicine and Public Health, Madison, WI
- Department of Radiology, University of Wisconsin School of Medicine and Public Health, Madison, WI
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12
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Preusche O. Choosing sensitivity to reduce X-ray dose in medical phase contrast imaging. OPTICS EXPRESS 2018; 26:10339-10357. [PMID: 29715972 DOI: 10.1364/oe.26.010339] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/24/2018] [Accepted: 04/06/2018] [Indexed: 06/08/2023]
Abstract
In medical X-ray imaging, phase contrast imaging is to measure refraction angles caused by the patient. The X-ray dose for a given image quality depends on the sensitivity of the setup, i.e. on the angular measurement range. Measurement ranges of existing phase contrast setups are either too high or too low for perfectly imaging a human finger in air: There is a gap in available measurement ranges, which prevents a reduction of X-ray dose. To fill the gap, this work proposes a novel variant of a Talbot-Lau interferometer. Instead of a single phase grating, it uses two phase gratings, each consisting of tiny prisms. The height of the prisms is an additional factor in the measurement range, which allows to fill the gap. The potential is a dose-reduction by a factor of 5.4 compared to Talbot-Lau setups of same post-patient length. Simulation results indicate a polychromatic visibility of up to 20%.
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Trabecular bone anisotropy imaging with a compact laser-undulator synchrotron x-ray source. Sci Rep 2017; 7:14477. [PMID: 29101369 PMCID: PMC5670213 DOI: 10.1038/s41598-017-14830-x] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2017] [Accepted: 10/18/2017] [Indexed: 02/01/2023] Open
Abstract
Conventional x-ray radiography is a well-established standard in diagnostic imaging of human bones. It reveals typical bony anatomy with a strong surrounding cortical bone and trabecular structure of the inner part. However, due to limited spatial resolution, x-ray radiography cannot provide information on the microstructure of the trabecular bone. Thus, microfractures without dislocation are often missed in initial radiographs, resulting in a lack or delay of adequate therapy. Here we show that x-ray vector radiography (XVR) can overcome this limitation and allows for a deeper insight into the microstructure with a radiation exposure comparable to standard radiography. XVR senses x-ray ultrasmall-angle scattering in addition to the attenuation contrast and thereby reveals the mean scattering strength, its degree of anisotropy and the orientation of scattering structures. Corresponding to the structural characteristics of bones, there is a homogenous mean scattering signal of the trabecular bone but the degree of anisotropy is strongly affected by variations in the trabecular structure providing more detailed information on the bone microstructure. The measurements were performed at the Munich Compact Light Source, a novel type of x-ray source based on inverse Compton scattering. This laboratory-sized source produces highly brilliant quasi-monochromatic x-rays with a tunable energy.
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14
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Improved middle-ear soft-tissue visualization using synchrotron radiation phase-contrast imaging. Hear Res 2017; 354:1-8. [DOI: 10.1016/j.heares.2017.08.001] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/22/2017] [Revised: 07/30/2017] [Accepted: 08/02/2017] [Indexed: 12/20/2022]
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Ji X, Ge Y, Zhang R, Li K, Chen GH. Studies of signal estimation bias in grating-based x-ray multicontrast imaging. Med Phys 2017; 44:2453-2465. [PMID: 28339107 DOI: 10.1002/mp.12235] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2016] [Revised: 03/08/2017] [Accepted: 03/12/2017] [Indexed: 11/08/2022] Open
Abstract
PURPOSE In grating-based x-ray multi-contrast imaging, signals of three contrast mechanisms-absorption contrast, differential phase contrast (DPC), and dark-field contrast-can be estimated from the same set of acquired data. The estimated signals, N0 (related to absorption), N1 (related to dark-field), and φ (related to DPC) may be intrinsically biased. However, it is yet unclear how large these biases are and how the data acquisition parameters affect the biases in the extracted signals. The purpose of this paper was to address these questions. METHODS The biases of the extracted signals (i.e., N0 , N1 and φ) were theoretically studied for a well-known signal estimation method. Experimental data acquired from a grating-based x-ray multi-contrast benchtop imaging system with a photon counting detector were used to validate the theoretical results for the signal biases of the three contrast mechanisms. RESULTS Both theoretical and experimental studies showed the following results: (1) The bias of signal estimation for the absorption contrast signal is zero; (2) The bias of signal estimation for N1 is inversely proportional to the number of phase steps and to the average fringe visibility of the grating interferometer, but the ratio between the bias and the signal level (i.e., the relative bias) is independent of the number of phase steps; (3) The bias of signal estimation for φ depends on the mean DPC signal level, the total exposure level of the multi-contrast data acquisition, and the mean fringe visibility of the interferometer. CONCLUSIONS In grating-based x-ray multi-contrast imaging, the estimated absorption contrast signal is unbiased; the estimated dark-field contrast signal is biased, but the relative bias is only dependent on the mean fringe visibility of the interferometer and the exposure level. The estimated DPC signal may be biased, and the bias level depends on the mean signal level, the exposure level, and the interferometer performance.
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Affiliation(s)
- Xu Ji
- Department of Medical Physics, University of Wisconsin School of Medicine and Public Health, Madison, WI, USA
| | - Yongshuai Ge
- Department of Medical Physics, University of Wisconsin School of Medicine and Public Health, Madison, WI, USA
| | - Ran Zhang
- Department of Medical Physics, University of Wisconsin School of Medicine and Public Health, Madison, WI, USA
| | - Ke Li
- Department of Medical Physics, University of Wisconsin School of Medicine and Public Health, Madison, WI, USA.,Department of Radiology, University of Wisconsin School of Medicine and Public Health, Madison, WI, USA
| | - Guang-Hong Chen
- Department of Medical Physics, University of Wisconsin School of Medicine and Public Health, Madison, WI, USA.,Department of Radiology, University of Wisconsin School of Medicine and Public Health, Madison, WI, USA
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Olatinwo MB, Ham K, McCarney J, Marathe S, Ge J, Knapp G, Butler LG. Recent applications of X-ray grating interferometry imaging to evaluate flame retardancy performance of brominated flame retardant. Polym Degrad Stab 2017. [DOI: 10.1016/j.polymdegradstab.2017.02.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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17
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George A, Chen PY, Morales-Martinez A, Panna A, Gomella AA, Bennett EE, Wen H. Geometric calibration and correction for a lens-coupled detector in x-ray phase-contrast imaging. J Med Imaging (Bellingham) 2017; 4:013507. [PMID: 28382313 DOI: 10.1117/1.jmi.4.1.013507] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2016] [Accepted: 03/02/2017] [Indexed: 11/14/2022] Open
Abstract
A lens-coupled x-ray camera with a tilted phosphor collects light emission from the x-ray illuminated (front) side of phosphor. Experimentally, it has been shown to double x-ray photon capture efficiency and triple the spatial resolution along the phosphor tilt direction relative to the same detector at normal phosphor incidence. These characteristics benefit grating-based phase-contrast methods, where linear interference fringes need to be clearly resolved. However, both the shallow incident angle on the phosphor and lens aberrations of the camera cause geometric distortions. When tiling multiple images of limited vertical view into a full-field image, geometric distortion causes blurring due to image misregistration. Here, we report a procedure of geometric correction based on global polynomial transformation of image coordinates. The corrected image is equivalent to one obtained with a single full-field flat panel detector placed at the sample plane. In a separate evaluation scan, the position deviations in the horizontal and vertical directions were reduced from 0.76 and 0.028 mm, respectively, to 0.006 and 0.009 mm, respectively, by the correction procedure, which were below the 0.028-mm pixel size of the imaging system. In a demonstration of a phase-contrast imaging experiment, the correction reduced blurring of small structures.
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Affiliation(s)
- Alex George
- National Institutes of Health , National Heart, Lung and Blood Institute, Biochemistry and Biophysics Center, Imaging Physics Laboratory, Bethesda, Maryland, United States
| | - Peter Y Chen
- National Institutes of Health , National Heart, Lung and Blood Institute, Biochemistry and Biophysics Center, Imaging Physics Laboratory, Bethesda, Maryland, United States
| | - Alejandro Morales-Martinez
- National Institutes of Health , National Heart, Lung and Blood Institute, Biochemistry and Biophysics Center, Imaging Physics Laboratory, Bethesda, Maryland, United States
| | - Alireza Panna
- National Institutes of Health , National Heart, Lung and Blood Institute, Biochemistry and Biophysics Center, Imaging Physics Laboratory, Bethesda, Maryland, United States
| | - Andrew A Gomella
- National Institutes of Health , National Heart, Lung and Blood Institute, Biochemistry and Biophysics Center, Imaging Physics Laboratory, Bethesda, Maryland, United States
| | - Eric E Bennett
- National Institutes of Health , National Heart, Lung and Blood Institute, Biochemistry and Biophysics Center, Imaging Physics Laboratory, Bethesda, Maryland, United States
| | - Han Wen
- National Institutes of Health , National Heart, Lung and Blood Institute, Biochemistry and Biophysics Center, Imaging Physics Laboratory, Bethesda, Maryland, United States
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18
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Marschner M, Birnbacher L, Mechlem K, Noichl W, Fehringer A, Willner M, Scherer K, Herzen J, Noël PB, Pfeiffer F. Two-shot X-ray dark-field imaging. OPTICS EXPRESS 2016; 24:27032-27045. [PMID: 27857430 DOI: 10.1364/oe.24.027032] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
In this article, we report on a novel acquisition scheme for time- and dose-saving retrieval of dark-field data in grating-based phase-contrast imaging. In comparison to currently available techniques, the proposed approach only requires two phase steps. More importantly, our method is capable of accurately retrieving the dark-field signal where conventional approaches fail, for instance in the case of very low photon statistics. Finally, we successfully extend two-shot dark-field imaging to tomographic investigations, by implementing an iterative reconstruction with appropriate weights. Our results indicate an important progression towards the clinical feasibility of dark-field tomography.
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19
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Preusche O. Lens gratings for dose optimization of medical X-ray phase contrast imaging. OPTICS EXPRESS 2016; 24:26161-26174. [PMID: 27857353 DOI: 10.1364/oe.24.026161] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
A novel way to build arrays of X-ray lenslets is proposed for use in medical imaging, in particular for X-ray phase contrast imaging. Focusing on Talbot-Lau interferometers, this work is about patient dose reduction, especially for design energies above 50 keV. A low dose poses a fabrication problem, because it requires an analyzer grating which is both fine and high: It has to be fine for a good angular sensitivity. It has to be high to absorb well. However, gratings can currently be built either fine or high. The proposed solution is to use a fine novel lens grating in front of a high analyzer grating: The lens grating uses lenslets to combine fine fringes into wider strips. This coarser pattern is then analyzed by a high grating. Regular binary production processes are sufficient to build lens gratings. Simulation-based results show that lens gratings can save dose with no impact on reconstructed images.
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20
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Miao H, Chen L, Mirzaeimoghri M, Kasica R, Wen H. Cryogenic Etching of High Aspect Ratio 400 nm Pitch Silicon Gratings. JOURNAL OF MICROELECTROMECHANICAL SYSTEMS : A JOINT IEEE AND ASME PUBLICATION ON MICROSTRUCTURES, MICROACTUATORS, MICROSENSORS, AND MICROSYSTEMS 2016; 25:963-967. [PMID: 27799726 PMCID: PMC5084849 DOI: 10.1109/jmems.2016.2593339] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
The cryogenic process and Bosch process are two widely used processes for reactive ion etching of high aspect ratio silicon structures. This paper focuses on the cryogenic deep etching of 400 nm pitch silicon gratings with various etching mask materials including polymer, Cr, SiO2 and Cr-on-polymer. The undercut is found to be the key factor limiting the achievable aspect ratio for the direct hard masks of Cr and SiO2, while the etch selectivity responds to the limitation of the polymer mask. The Cr-on-polymer mask provides the same high selectivity as Cr and reduces the excessive undercut introduced by direct hard masks. By optimizing the etching parameters, we etched a 400 nm pitch grating to ≈ 10.6 μm depth, corresponding to an aspect ratio of ≈ 53.
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Affiliation(s)
- Houxun Miao
- National Institutes of Health, Bethesda, MD 20892 USA
| | - Lei Chen
- National Institute of Standards and Technology, Gaithersburg, MD 20899 USA
| | | | - Richard Kasica
- National Institute of Standards and Technology, Gaithersburg, MD 20899 USA
| | - Han Wen
- National Institutes of Health, Bethesda, MD 20892 USA
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21
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Miao H, Panna A, Gomella AA, Bennett EE, Znati S, Chen L, Wen H. A Universal Moiré Effect and Application in X-Ray Phase-Contrast Imaging. NATURE PHYSICS 2016; 12:830-834. [PMID: 27746823 PMCID: PMC5063246 DOI: 10.1038/nphys3734] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
A moiré pattern is created by superimposing two black-and-white or gray-scale patterns of regular geometry, such as two sets of evenly spaced lines. We observed an analogous effect between two transparent phase masks in a light beam which occurs at a distance. This phase moiré effect and the classic moiré effect are shown to be the two ends of a continuous spectrum. The phase moiré effect allows the detection of sub-resolution intensity or phase patterns with a transparent screen. When applied to x-ray imaging, it enables a polychromatic far-field interferometer (PFI) without absorption gratings. X-ray interferometry can non-invasively detect refractive index variations inside an object1-10. Current bench-top interferometers operate in the near field with limitations in sensitivity and x-ray dose efficiency2, 5, 7-10. The universal moiré effect helps overcome these limitations and obviates the need to make hard x-ray absorption gratings of sub-micron periods.
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Affiliation(s)
- Houxun Miao
- Biophysics and Biochemistry Center, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, Maryland, USA
| | - Alireza Panna
- Biophysics and Biochemistry Center, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, Maryland, USA
| | - Andrew A Gomella
- Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, Pennsylvania, USA
| | - Eric E Bennett
- Biophysics and Biochemistry Center, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, Maryland, USA
| | - Sami Znati
- Biophysics and Biochemistry Center, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, Maryland, USA
| | - Lei Chen
- Center for Nanoscale Science and Technology, National Institute of Standards and Technology, Gaithersburg, Maryland, USA
| | - Han Wen
- Biophysics and Biochemistry Center, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, Maryland, USA
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