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Spatial frequency-dependent pulse-height spectrum and method for analyzing detector DQE(f) from ensembles of single X-ray images

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MEDICAL PHYSICS 2022年第1期49卷 107-128页

作者： Dow, Scott Howansky, Adrian Lubinsky, Anthony R. Zhao, Wei SUNY Stony Brook Dept Radiol L-4120 Hlth Sci Ctr New York NY 11790 USA

Purpose Scintillators and photoconductors used in energy integrating detectors (EIDs) have inherent variations in their imaging response to single-detected X-rays due to variations in X-ray energy deposition and secondary quanta generation and transport, which degrades DQE(f). The imaging response of X-ray scintillators to single X-rays may be recorded and studied using single X-ray imaging (SXI) experiments;however, no method currently exists for relating SXI experimental results to EID DQE(f). This work proposes a general analytical framework for computing and analyzing the DQE(f) performance of EIDs from single X-ray image ensembles using a spatial frequency-dependent pulse-height spectrum. Methods A spatial frequency (f)-dependent gain, g similar to(f), is defined as the Fourier transform of the imaging response of an EID to a single-detected X-ray. A f-dependent pulse-height spectrum, Pr[g similar to(f)], is defined as the 2D probability density function of g similar to(f) over the complex plane. Pr[g similar to(f)] is used to define a f-dependent Swank factor, A(S)(f), which fully characterizes the DQE(f) degradation due to single X-ray noise. A(S)(f) is analyzed in terms of its degradation due to Swank noise, variations in the frequency-dependent attenuation of |g similar to(f)|, and noise in argg similar to(f) which occurs due to variations in the asymmetry in each single X-ray's imaging response. Three example imaging systems are simulated to demonstrate the impact of depth-dependent variation in g similar to(f), remote energy deposition, and a finite number of secondary quanta, on Pr[g similar to(f)], A(S)(f), MTF(f), and NPS(f)/NPS(0), which are computed from ensembles of single X-ray images. The same is also demonstrated by simulating a realistic imaging system;that is, a Gd2O2S-based EID. Using the latter imaging system, the convergence of A(S)(f) estimates is investigated as a function of the number of detected X-rays per ensemble. Results Depth-depend

关键词： detective quantum efficiency energy integrating detector modulation transfer function noise power spectrum pulse-height spectrum

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Performance of Ultra-High-Resolution Computed Tomography in Super High-Resolution Mode at the Routine Radiation Dose: Phantom Study

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JOURNAL OF COMPUTER ASSISTED TOMOGRAPHY 2022年第6期46卷 900-905页

作者： Kitera, Nobuo Fujioka, Chikako Higaki, Toru Nishimaru, Eiji Yokomachi, Kazushi Kiguchi, Masao Awai, Kazuo Hiroshima Univ Hosp Dept Radiol Hiroshima Japan Hiroshima Univ Grad Sch Biomed & Hlth Sci Dept Diagnost Radiol Hiroshima Japan Hiroshima Univ Hosp Dept Radiol 1-2-3 KasumiMinami Ku Hiroshima 7348551 Japan

ObjectiveUsing a chest phantom, we compared the image quality of ultra-high-resolution computed tomography (U-HRCT) images acquired in super high-resolution (SHR) and normal resolution (NR) mode and at the routine radiation dose. The detector size was 0.25 and 0.5 mm, *** chest phantom was scanned on a U-HRCT scanner. The scan parameters were tube voltage 120 kV and volume CT dose index 13.0 mGy, the routine radiation dose for conventional scans. The rotation time was 0.5 s/rot, the number of matrices was 512 in NR and 1024 in SHR mode. For physical evaluation, the modulation transfer function was measured on the spherical simulated nodule, and the noise power spectrum on the cylindrical water phantom. A CT value profile curve was created using an in-house simulated bronchial phantom. For visual evaluation, 3 radiologists and 3 radiology technologists evaluated overall image quality using a 4-grade scale (grade 1, poor;and grade 4, excellent).ResultsThe 10% of modulation transfer function was 13.5 lp/cm in NR and 14.9 lp/cm in SHR mode (P<0.01). integral(peak) was 5.6 lp/cm in NR and 8.8 lp/cm in SHR mode (P<0.01), and the peak of noise power spectrum shifted. On the profile curves, the CT value at the edge changed in NR but not in SHR mode. The overall image quality was grade 3.0 +/- 0.7 in SHR and grade 2.0 +/- 0.7 in NR mode (P<0.01).ConclusionsThe image quality of SHR mode with U-HRCT was superior to that of NR mode at the routine radiation dose.

关键词： ultra-high-resolution computed tomography image quality super high-resolution mode spatial resolution radiation dose CT-AEC CT-automatic exposure control D-FOV display field-of-view NPS noise power spectrum MTF modulation transfer function ROI region of interest SHR mode U-HRCT

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Reconstruction and calibration methods for a Mueller channeled spectropolarimeter

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OPTICS EXPRESS 2022年第2期30卷 2018-2032页

作者： Zhou, Guodong Li, Yanqiu Liu, Ke Beijing Inst Technol Sch Opt & Photon Key Lab Photoelect Imaging Technol & Syst Minist Educ China 5 South Zhongguancun St Beijing 100081 Peoples R China Beijing Inst Technol Inst Engn Med 5 South Zhongguancun St Beijing 100081 Peoples R China

Channeled spectropolarimeter (CSP) measures spectrally resolved Stokes vector of light and Mueller matrix of sample from a snapshot. While reconstruction and calibration methods for Stokes CSP have been well established, their Mueller CSP counterparts are lacking. In this paper, we propose methods for Mueller spectrum reconstruction and Mueller CSP calibration. Mueller CSP is modeled as a modulation matrix, linking the Mueller spectrum to be measured and the modulated spectrum from the spectrometer. We describe an optimization problem to solve the Mueller spectrum, where both the regularizer and the residual threshold constrain the result, making our reconstruction accurate, efficient, and noise-robust. The Stokes spectrum generated by polarization state generator and the analyzing vector of polarization state analyzer are measured in situ, the convolution of which construct the calibrated modulation matrix of Mueller CSP. Total polarimetric errors and spectroscopic errors are treated as a whole and represented by the calibrated modulation matrix. Both imaging and non-imaging Mueller CSP are experimentally calibrated. Reconstruction results show high accuracy with a root-mean-square error (RMSE) of 0.0371. The proposed methods help make Mueller CSP practical and have the potential to be general reconstruction and calibration methods for imaging and non-imaging Stokes-Mueller CSP. (C) 2022 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement

关键词： Calibration Extinction ratios Image reconstruction modulation transfer function Mueller matrices Optical elements

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High-quality telecentric projection lens for vein visualization

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JOURNAL OF OPTICAL TECHNOLOGY 2022年第6期89卷 339-345页

作者： Tuan, L. D. Duong, T., V Tu, L. A. Thuan, D. N. Kirillovskii, V. K. Le Quy Don Tech Univ Hanoi Vietnam Vietnam Acad Sci & Technol Inst Mat Sci Hanoi Vietnam ITMO Univ St Petersburg Russia

Subject of study. A design of high-quality telecentric projection lenses that can be integrated into a miniprojector for projecting vein images onto human skin surfaces was investigated. Method. A numerical method based on Zemax software was used to design the lens. The required corrections were performed computationally to obtain a lens with components of similar diameter, significantly simplifying the mechanical structure, thus enabling easy and economical mass production. Main results. The new telecentric projection lens comprises seven spherical lenses, with a focal length and f-number of 20 mm and 2.51, respectively. The obtained value of the modulation transfer function (MTF) is extremely high: approximately 0.8 at 471ines/mm and higher than 0.5 at 100 lines/mm. Relative distortion of the lens is less than 0.5% for the entire field of view. Owing to a unique technological feature, the fabricated projection lens demonstrated the measured MTF that was practically equal to the value calculated in the design. Practical significance. Using this projection lens in the vein finder enables the projection of sharp and precise images of veins onto the skin surface. Therefore, this device can help medical personnel in performing accurate and safe venipuncture. Owing to its low cost, compactness, and high quality of image formation, this projection lens is suitable for commercial purposes and for different applications of image formation. (C) 2022 Optica Publishing Group

关键词： Digital micromirror devices Distortion Image metrics modulation transfer function Spherical lenses Visible light

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Laplacian pyramid networks: A new approach for multispectral pansharpening

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INFORMATION FUSION 2022年第0期78卷 158-170页

作者： Jin, Cheng Deng, Liang-Jian Huang, Ting-Zhu Vivone, Gemine Univ Elect Sci & Technol China Sch Optoelect Sci & Engn Chengdu 611731 Peoples R China Univ Elect Sci & Technol China Sch Math Sci Chengdu 611731 Peoples R China CNR IMAA Inst Methodol Environm Anal I-85050 Tito Italy

Pansharpening is about fusing a high spatial resolution panchromatic image with a simultaneously acquired multispectral image with lower spatial resolution. In this paper, we propose a Laplacian pyramid pansharpening network architecture for accurately fusing a high spatial resolution panchromatic image and a low spatial resolution multispectral image, aiming at getting a higher spatial resolution multispectral image. The proposed architecture considers three aspects. First, we use the Laplacian pyramid method whose blur kernels are designed according to the sensors' modulation transfer functions to separate the images into multiple scales for fully exploiting the crucial spatial information at different spatial scales. Second, we develop a fusion convolutional neural network (FCNN) for each scale, combining them to form the final multi-scale network architecture. Specifically, we use recursive layers for the FCNN to share parameters across and within pyramid levels, thus significantly reducing the network parameters. Third, a total loss consisting of multiple across scale loss functions is employed for training, yielding higher accuracy. Extensive experimental results based on quantitative and qualitative assessments exploiting benchmarking datasets demonstrate that the proposed architecture outperforms state-of-the-art pansharpening methods. Code is available at https://***/ ChengJin-git/LPPN.

关键词： Laplacian pyramid modulation transfer function Convolutional neural network Pansharpening Image fusion Machine learning Remote sensing

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Optical-Quality Analysis and Defocus-Curve Simulations of a Novel Hydrophobic Trifocal Intraocular Lens

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CLINICAL OPHTHALMOLOGY 2023年 17卷 3915-3923页

作者： Labuz, Grzegorz Yan, Weijia Khoramnia, Ramin Auffarth, Gerd U. Univ Hosp Heidelberg David J Apple Ctr Vis Res Dept Ophthalmol D-69120 Heidelberg Germany Univ Klinikum Heidelberg Neuenheimer Feld 400 D-69120 Heidelberg Germany

Purpose: The optical function of a novel refractive-diffractive trifocal intraocular lens (IOL) was tested in vitro to provide preclinical metrics that predict postoperative performance and may guide patient ***: Fundamental optical characteristics of a trifocal hydrophobic-acrylic IOL with a C-loop haptic configuration (AT ELANA 841P, Carl Zeiss Meditec) were assessed using a fully automated optical test device under both monochromatic and polychromatic conditions combined with increased or compensated spherical aberration (SA). The area under the modulation transfer function (MTFa) was calculated across a defocus range from +1D to -3.5D and used to simulate visual acuity (VA). A polychromatic point spread function (PSF) was employed to assess the light distribution and identify photic ***: The highest MTFa values were obtained under monochromatic conditions using an SA-neutral corneal model. Nevertheless, after introducing SA and polychromatic light, the IOL performance remained good. Simulated VA values were 0.00 logMAR for distance, 0.1 logMAR at 100 cm, and progressively improving to 0.05 logMAR at 40 cm from the intermediate point. The light-spread analysis confirmed halos around the PSF center, which is a characteristic of trifocal ***: AT ELANA 841P demonstrated good optical performance across various distances, independently of spectral and SA conditions, resulting in good simulated VA. Although light spread resembles standard trifocal IOLs, clinical studies are essential to confirm these laboratory results.

关键词： intraocular lenses presbyopia correction optical quality modulation transfer function

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Experimental measurement of the meridian Petzval image plane of a streak tube

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APPLIED OPTICS 2022年第33期61卷 9825-9831页

作者： Zhang, Jing-Jin Zong, Fang-Ke NIu, Li-Hong Yang, Qin-Lao Cai, Hou-Zhi Shenzhen Univ Coll Phys & Optoelect Engn Shenzhen 518060 Peoples R China Inst Adv Sci Facil Shenzhen 518106 Peoples R China

For an electron-optical imaging system with wide beam focusing, the calculation of the field curvature can be performed only theoretically and requires the specific analytical expressions of the axial potential distribution in the streak tube and its corresponding derivatives, making the calculation cumbersome. Even when the electron trajectory is tracked using the numerical calculation method, the calculated results cannot be verified experimentally. A method for measuring the field curvature of the streak tube based on the spherical fluorescent screen is proposed for the first time, to the best of our knowledge. This method can directly measure the field curvature from the experimental image without requiring information on the internal structure of the streak tube, which is extremely useful for the design of the subsequent image reconstruction algorithm. (c) 2022 Optica Publishing Group

关键词： Image reconstruction Image resolution modulation transfer function Reconstruction algorithms Streak cameras Ultrafast devices

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High linearity silicon DC Kerr modulator enhanced by slow light for 112 Gbit/s PAM4 over 2 km single mode fiber transmission

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OPTICS EXPRESS 2022年第10期30卷 16996-17007页

作者： Xia, Penghui Yu, Hui Zhang, Qiang Wang, Xiaofei Fu, Zhilei Huang, Qikai Ning, Nannan Wei, Zhujun Jiang, Xiaoqing Yang, Jianyi Zhejiang Univ Coll Informat Sci & Elect Engn Inst Microelect & Nanoelect Hangzhou 310027 Peoples R China Zhejiang Lab Hangzhou 311121 Peoples R China

We demonstrate a high efficiency, high linearity and high-speed silicon Mach-Zehnder modulator based on the DC Kerr effect enhanced by slow light. The two modulation arms based on 500-tun-long grating waveguides are embedded with PN and PIN junctions, respectively. A comprehensive comparison between the two modulation arms reveals that insertion loss, bandwidth and modulation linearity are improved significantly after employing the DC Kerr effect. The complementary advantages of the slow light and the DC Kerr effect enable a modulation efficiency of 0.85 ***, a linearity of 115 ***(2/3), and a bandwidth of 30 GHz when the group index of slow light is set to 10. Furthermore, 112 Gbitls PAM4 transmission over 2 km standard single mode fiber (SSMF) with bit error ratio (BER) below the soft decision forward error correction (SD-FEC) threshold is also demonstrated. (C) 2022 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement

关键词： Effective refractive index Kerr effect Light matter interactions modulation transfer function Silicon modulators Single mode fibers

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Hardware analysis for motion estimation task

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APPLIED OPTICS 2022年第15期61卷 4303-4314页

作者： Cohen, Khen Hodeda, Gal Almog, Emmanuel Raviv, Dan Mendlovic, David Tel Aviv Univ Fac Engn Dept Elect Engn IL-69978 Tel Aviv Israel

This work introduces hardware metrics to evaluate imaging sensor (camera) ability to cope with temporal change (motion). Shifting from images towards moving elements demands better tools for evaluation than just refresh rate, and this work is here to close that gap. We focus on the sampling frequency, signal to noise ratio, rolling shutter, and modulation transfer function as a set of parameters to define four fundamental conditions to evaluate and compare the quality of motion sensing. We further examine our theory on existing hardware used in modern equipment and report our findings. (C) 2022 Optica Publishing Group

关键词： Image sensors Machine vision modulation transfer function Motion estimation Neural networks Optical flow

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Quantitative measurements of emphysema in ultra-high resolution computed tomography using model-based iterative reconstruction in comparison to that using hybrid iterative reconstruction

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PHYSICAL AND ENGINEERING SCIENCES IN MEDICINE 2022年第1期45卷 115-124页

作者： Muramatsu, Shun Sato, Kazuhiro Yamashiro, Tsuneo Doi, Kunio Ohara Gen Hosp Dept Radiol 6-1 Ue Machi Fukushima Fukushima 9608611 Japan Tohoku Univ Grad Sch Med Hlth Sci Aoba Ku 2-1 Seiryo Machi Sendai Miyagi 9808575 Japan Yokohama City Univ Dept Diagnost Radiol Kanazawa Ku 3-9 Fukuura Yokohama Kanagawa 2360004 Japan Univ Chicago Dept Radiol 5841 Maryland Av Chicago IL 60637 USA Gunma Prefectural Coll Hlth Sci 323-1 Kamioki Machi Maebashi Gunma 3710052 Japan

The percentage of low attenuation volume ratio (LAVR), which is measured using computed tomography (CT), is an index of the severity of emphysema. For LAVR evaluation, ultra-high-resolution (U-HR) CT images are useful. To improve the image quality of U-HRCT, iterative reconstruction is used. There are two types of iterative reconstruction: hybrid iterative reconstruction (HIR) and model-based iterative reconstruction (MBIR). In this study, we physically and clinically evaluated U-HR images reconstructed with HIR and MBIR, and demonstrated the usefulness of U-HR images with MBIR for quantitative measurements of emphysema. Both images were reconstructed with a slice thickness of 0.25 mm and an image matrix size of 1024 x 1024 pixels. For physical evaluation, the modulation transfer function (MTF) and noise power spectrum (NPS) of HIR and MBIR were compared. For clinical evaluation, LAVR calculated from HIR and MBIR were compared using the Wilcoxon matched-pairs signed-rank test. In addition, the correlation between LAVR and forced expiratory volume in one second (FEV1%) was evaluated using the Spearman rank correlation test. The MTFs of HIR and MBIR were comparable. The NPS of MBIR was lower than that of HIR. The mean LAVR values calculated from HIR and MBIR were 19.5 +/- 12.6% and 20.4 +/- 11.7%, respectively (p = 0.84). The correlation coefficients between LAVR and FEV1% that were taken from HIR and MBIR were 0.64 and 0.74, respectively (p < 0.01). MBIR is more useful than HIR for the quantitative measurements of emphysema with U-HR images.

关键词： Model based iterative reconstruction Chronic obstructive pulmonary disease Ultra-high-resolution modulation transfer function Noise power spectrum Hybrid iterative reconstruction

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