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Comparison of noise-power spectrum and modulation-transfer function for CT images reconstructed with iterative and deep learning image reconstructions: An initial experience study

Setiawan Adiwasono M. B., Anam Choirul, Hidayanto Eko, Sutanto Heri, Naufal Ariij, Dougherty Geoff

Polish Journal of Medical Physics and Engineering

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2023

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Vol. 29, Iss. 2

104--112

EN

Deep learning image reconstruction (DLIR) is a very recent image reconstruction method that is already available for commercial use. We evaluated the quality of DLIR images and compared it to the quality of images from the latest adaptive statistical iterative reconstruction (ASIR-V) algorithm in terms of noise-power spectrum (NPS) and modulation-transfer function (MTF). We scanned a Revolution QA phantom (GE Healthcare, USA) and a 20 cm water phantom (GE Healthcare, USA) with our 512 multi-slice computed tomography (CT) scanner. Images of the tungsten wire within the Revolution QA phantom were reconstructed with a 50 mm field of view (FOV). The images were reconstructed with various ASIR-V strengths (i.e. 0, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100%) and DLIRs (i.e. low, medium, and high) to assess the MTF. The images from the 20 cm water phantom were reconstructed with the same configuration to assess the NPS. The MTF was similar for both reconstruction algorithms of DLIR and ASiR-V. The peak frequency (fp) of the DLIR low was comparable to that from ASIR-V at 50, 60, 70%; the DLIR medium was comparable to ASIR-V at 80%; and the DLIR high was comparable to ASIR-V at 100%. The average frequency (fA) of the DLIR low was comparable to that from ASIR-V at 40%; the DLIR medium was comparable to ASIR-V at 50%; and the DLIR high was comparable to ASIR-V at 70%. Both the DLIR and ASIR-V were able to reduce noise, but they had a different texture. The noise in the DLIR images was more homogenous at high and low frequencies, while in the ASIR-V images, the noise was more concentrated at high frequencies. The MTF was similar for both reconstruction algorithms. The DLIR method showed a better noise reduction than the ASIR-V reconstruction.

2

Discussion around IR material and structure issues to go toward high performance small pixel pitch IR HOT FPAs

Gravrand Olivier, Baier Nicolas, Ferron Alexandre, Rochette Florent, Lobre Clément, Bertoz Jocelyn, Rubaldo Laurent

Opto-Electronics Review

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2023

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Vol. 31, Special Issue

art. no. e144561

EN

In the last decade, infrared imaging detectors trend has gone for smaller pixels and larger formats. Most of the time, this scaling is carried out at a given total sensitive area for a single focal plane array. As an example, QVGA 30 μm pitch and VGA 15 μm pitch exhibit exactly the same sensitive area. SXGA 10 μm pitch tends to be very similar, as well. This increase in format is beneficial to image resolution. However, this scaling to even smaller pixels raises questions because the pixel size becomes similar to the IR wavelength, but also to the typical transport dimensions in the absorbing material. Hence, maintaining resolution for such small pixel pitches requires a good control of the modulation transfer function and quantum efficiency of the array, while reducing the pixel size. This might not be obtained just by scaling the pixel dimensions. As an example, bulk planar structures suffer from excessive lateral diffusion length inducing pixel-to-pixel cross talk and thus degrading the modulation transfer function. Transport anisotropy in some type II superlattice structures might also be an issue for the diffusion modulation transfer function. On the other side, mesa structures might minimize cross talk by physically separating pixels, but also tend to degrade the quantum efficiency due to a non-negligible pixel fill factor shrinking down the pixel size. This paper discusses those issues, taking into account different material systems and structures, in the perspective of the expected future pixel pitch infrared focal plane arrays.

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Determination of DQE as a quantitative assessment of detectors in digital mammography: Measurements and calculation in practice

Wysocka-Rabin Anna, Dobrzyńska Magdalena, Pasicz Katarzyna, Skrzyński Witold, Fabiszewska Ewa

Polish Journal of Medical Physics and Engineering

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2021

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Vol. 27, Iss. 3

223--232

EN

Introduction: Advances in digital detector technology and methods of image presentation in digital mammography now offer the possibility of implementing mathematical assessment methods to quantitative image analysis. The aim of this work was to develop new software to simplify the application of the existing international standard for DQE in digital mammography and show in detail how it can be applied, using a Siemens Mammomat Inspiration as a model. Material and methods: Consistent with the IEC standard a 2 mm Al filter at the tube exit and images in DICOM format as raw data, without applying any additional post-processing were used. Measurements were performed for W/Rh anode/filter combination and different tube voltage values (26 ÷ 34 kV) without any anti-scatter grid. To verify new software doses ranging from 20-600 μGy were used in measurements. Exposure (air kerma) was measured using a calibrated radiation meter (Piranha Black 457, RTI Electronics AB, Sweden). MTF was determined, using an edge test device constructed specifically for this work. Results: It has been demonstrated that with the new software the DQE can be measured with the accuracy required by the international standard IEC 62220-1-2. DQE has been presented as a function of spatial frequency for W/Rh anode/filter combination and different tube voltage. Conclusions: New software was used successfully to analyze image quality parameters for the Siemens Mammomat Inspiration detector. This was done on the basis of an internationally accepted methodology. In the next step, mammographs with different detector types can be compared.

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Automated MTF measurement in CT images with a simple wire phantom

Anam Choirul, Fujibuchi Toshioh, Haryanto Freddy, Budi Wahyu Setia, Sutanto Heri, Adi Kusworo, Muhlisin Zaenul, Dougherty Geoff

Polish Journal of Medical Physics and Engineering

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2019

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Vol. 25, Iss. 3

179--187

EN

This study developed a simple wire phantom and an algorithm to automatically measure the modulation transfer function (MTF) in computed tomography (CT) and implemented it to evaluate the effect of focal spot size and reconstruction filter type. The phantom consisted of a resin cylinder filled with water, with a tin wire of diameter 0.1 mm positioned along the center of the cylinder. The automated MTF algorithm used an axial image of the phantom and comprised several steps. The center position of a region of interest (ROI) was automatically determined at the center of the wire image. The pixels were then summed along the y-direction to obtain the profile of the pixel values at a point along the x-direction. Following this, both edges of the profile were made equal to zero. The profile curve was then normalized so that the total of all the data was equal to unity. The normalized profile curve is the line spread function (LSF), and the MTF curve was obtained by taking its Fourier transform. Our system (phantom and algorithm) is able to differentiate the MTFs of CT images from different focal sizes and reconstruction filter types.

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Influence of glistening and calcium deposits in artificial intraocular lenses on retinal image quality – numerical model

Geniusz M., Zajac M.

Optica Applicata

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2017

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Vol. 47, nr 3

341--350

EN

In modern ophthalmology the natural eye lens is sometimes replaced with an artificial implant – intraocular lens which remains in the eye for a long time. This can lead to the formation of numerous microdefects occurring on the intraocular lens surface or inside its volume. The most common include calcium deposits or microvacuoles referred to as glistenings. The presence of those defects causes deterioration of retinal image thus lowering the quality of vision. The purpose of this research is to develop a numerical model of human eye with intraocular lens burden with defects useful to predict the impact of calcium deposits and glistenings on the retinal image quality. The calculations made in accordance with this model suggest that the quality of retinal image deteriorates when the density of defects increases, but the degree of image deterioration does not depend on the location of the defects and transmittance of individual particles. The main deterioration effect is observed for low spatial frequencies (< 12 cycles/deg) both in case of calcium deposits and glistenings while for the spatial frequency of 30 cycles/deg the changes in modulation transfer function are insignificant. The presence of microvacuoles in the intraocular lens influences the worsening of modulation transfer function parameters only for the diameter of microvacuoles greater than 10 μm.

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Space remote sensing systems transmission capabilities modeling

Burshtynska K., Dolynska I.

Geomatics, Landmanagement and Landscape

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2013

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no. 3

27--35

EN

Space information, or information obtained by means of space remote sensing, is widely and effectively used by many countries to solve a lot of scientific, technical and applied problems. Most manufacturers of space remote sensing systems declared the high resolution values of their systems. However, these values are computed theoretically, without considering the various factors affected them. To determine the real resolution of the system, we have considered mathematical modeling which describes the influence of different factors on the satellite images resolution. Some of these factors are: atmosphere turbulence, image shift, residual defocusing, and diffraction. One of the most important characteristic of the images resolution is the modulation transfer function (MTF) which allows the estimation of different factors affected on the image resolution. The modulation transfer function (MTF) is a fundamental tool for assessing the performance of imaging systems. Various authors [Zhang et al. 2012, Hwang et al. 2008, Ryan et al. 2003] investigate diferent MTF assessment methods of high resolution satellite images: a slant-edge method, a knife-edge method, a sine wave method and a grill pattern. We propose a generalized approach for MTF assessment based on theoretical assumptions which allows to determine the inluence of diferent factors. A comparative analysis of the modulation transfer function(s) for different space imaging systems shows that the image resolution depends mainly on the atmosphere turbulence and size of a sensor element. Additionally, we established that atmospheric turbulence significantly reduces the transmitting possibility of images. The parameters which describe the influence of turbu¬lence required additional studies. The main goal of our researches is to show that real spatial image(s) resolution is much "inferior" than the value provided by the manufacturers of space remote sensing systems.

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Analiza porównawcza własności akustycznych sali konferencyjnej na podstawie pomiarów rzeczywistych i symulacji komputerowej w programie EASE 3.0. cześć pierwsza . "Pomiary"

Kowal R.

Bezpieczeństwo i Technika Pożarnicza

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2006

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Nr 1

55-60

PL

W pierwszej części artykułu omówiono na przykładzie "Sali Konferencyjnej" podstawy postępowania przy wykonywaniu pomiarów akustycznych wnętrz, celem porównania rzeczywistych wyników badań z symulacją komputerową.

EN

In order to compare the gathered results with computational simulation, it has been discussed in this article the fundamentals of acoustic measurements procedure within building premises basing on the Conference Hall as an example.