Polar coordinate coherent passive acoustic beamforming for the modifiable improvement of image quality and field of view

2021 ◽  
Author(s):  
Chunqi Li ◽  
Harry R. Clegg ◽  
Thomas M. Carpenter ◽  
Luzhen Nie ◽  
Steven Freear ◽  
...  
Keyword(s):  
Image Quality ◽  
Field Of View ◽  
Polar Coordinate ◽  
Passive Acoustic

scholarly journals Cone-Beam Computed Tomography and Radiographs in Dentistry: Aspects Related to Radiation Dose

2012 ◽  
Vol 2012 ◽  
pp. 1-10 ◽  
Author(s):  
Diego Coelho Lorenzoni ◽  
Ana Maria Bolognese ◽  
Daniela Gamba Garib ◽  
Fabio Ribeiro Guedes ◽  
Eduardo Franzotti Sant’Anna
Keyword(s):  
Computed Tomography ◽  
Image Quality ◽  
Radiation Dose ◽  
Cone Beam Computed Tomography ◽  
Field Of View ◽  
Cone Beam ◽  
Special Focus ◽  
Radiation Doses ◽  
Lower Effective Dose ◽  
Plain Radiographs

Introduction. The aim of this study was to discuss the radiation doses associated with plain radiographs, cone-beam computed tomography (CBCT), and conventional computed tomography (CT) in dentistry, with a special focus on orthodontics.Methods. A systematic search for articles was realized by MEDLINE from 1997–March 2011.Results. Twenty-seven articles met the established criteria. The data of these papers were grouped in a table and discussed.Conclusions. Increases in kV, mA, exposure time, and field of view (FOV) increase the radiation dose. The dose for CT is greater than other modalities. When the full-mouth series (FMX) is performed with round collimation, the orthodontic radiographs transmit higher dose than most of the large FOV CBCT, but it can be reduced if used rectangular collimation, showing lower effective dose than large FOV CBCT. Despite the image quality, the CBCT does not replace the FMX. In addition to the radiation dose, image quality and diagnostic needs should be strongly taken into account.

Evaluation of digital and film hemispherical photography and spherical densiometry for measuring forest light environments

2000 ◽  
Vol 30 (12) ◽  
pp. 1999-2005 ◽  
Author(s):  
Sylvia R Englund ◽  
Joseph J O'Brien ◽  
David B Clark
Keyword(s):  
Image Quality ◽  
Computer Analysis ◽  
Digital Image ◽  
Digital Images ◽  
Optical Quality ◽  
Field Of View ◽  
Canopy Openness ◽  
Hemispherical Photography ◽  
Site Factor ◽  
Film Images

This study presents the results of a comparison of digital and film hemispherical photography as means of characterizing forest light environments and canopy openness. We also compared hemispherical photography to spherical densiometry. Our results showed that differences in digital image quality due to the loss of resolution that occurred when images were processed for computer analysis did not affect estimates of unweighted openness. Weighted openness and total site factor estimates were significantly higher in digital images compared with film photos. The differences between the two techniques might be a result of underexposure of the film images or differences in lens optical quality and field of view. We found densiometer measurements significantly increased in consistency with user practice and were correlated with total site factor and weighted-openness estimates derived from hemispherical photography. Digital photography was effective and more convenient and inexpensive than film cameras, but until the differences we observed are better explained, we recommend caution when comparisons are made between the two techniques. We also concluded that spherical densiometers effectively characterize forest light environments.

scholarly journals The effect of modern PET technology and techniques on the EANM paediatric dosage card

2021 ◽  
Author(s):  
John Dickson ◽  
Uta Eberlein ◽  
Michael Lassmann
Keyword(s):  
Image Quality ◽  
Field Of View ◽  
Published Data ◽  
Axial Field ◽  
Short Article ◽  
Pet Ct ◽  
Class B ◽  
Total Body ◽  
Bed Position ◽  
Pet Scanners

Abstract Aim Recent advancements in PET technology have brought with it significant improvements in PET performance and image quality. In particular, the extension of the axial field of view of PET systems, and the introduction of semiconductor technology into the PET detector, initially for PET/MR, and more recently available long-field-of-view PET/CT systems (≥ 25 cm) have brought a step change improvement in the sensitivity of PET scanners. Given the requirement to limit paediatric doses, this increase in sensitivity is extremely welcome for the imaging of children and young people. This is even more relevant with PET/MR, where the lack of CT exposures brings further dose reduction benefits to this population. In this short article, we give some details around the benefits around new PET technology including PET/MR and its implications on the EANM paediatric dosage card. Material and methods  Reflecting on EANM adult guidance on injected activities, and making reference to bed overlap and the concept of MBq.min bed−1 kg−1, we use published data on image quality from PET/MR systems to update the paediatric dosage card for PET/MR and extended axial field of view (≥ 25 cm) PET/CT systems. However, this communication does not cover the expansion of paediatric dosing for the half-body and total-body scanners that have recently come to market. Results In analogy to the existing EANM dosage card, new parameters for the EANM paediatric dosage card were developed (class B, baseline value: 10.7 MBq, minimum recommended activity 10 MBq). The recommended administered activities for the systems considered in this communication range from 11 MBq [18F]FDG for a child with a weight of 3 kg to 149 MBq [18F]FDG for a paediatric patient weight of 68 kg, assuming a scan of 3 min per bed position. The mean effective dose over all ages (1 year and older) is 2.85 mSv. Conclusion With this, recommendations for paediatric dosing are given for systems that have not been considered previously.

Ахроматизированные объективы тепловизоров

2020 ◽  
Vol 14 (4) ◽  
pp. 360-367
Author(s):  
И.П. Шишкин ◽  
А.П. Шкадаревич
Keyword(s):  
Image Quality ◽  
Thermal Imaging ◽  
Infrared Region ◽  
Field Of View ◽  
Pixel Size ◽  
Variable Focus

Дано описание конструкции ахроматизированных объективов, работающих в ИК‑области спектра (8–12 мкм). При проектировании тепловизионных объективов необходимо учитывать тот факт, что размер пиксела современных микроболометров составляет 10–12 мкм, а плотность пикселей достигла формата 1 280 × 1 024. Эти параметры определяют более высокие требования, предъявляемые к качеству изображения, разрешающей способности и полю зрения разрабатываемого объектива. При этом объектив должен быть светосильным, термостабилизированным и иметь фокусировку. Рассмотрены объективы: 4-линзовый с фокусом 50 мм, 3-линзовый с фокусом 150 мм и 7-линзовый с переменным фокусом 30–150 мм. A description is given of the design of achromatized lenses operating in the infrared region of the spectrum (8–12 μm). When designing thermal imaging lenses, it is necessary to take into account the fact that the pixel size of modern microbolometers is 10–12 μm, and the pixel density has reached 1280 × 1024 format. These parameters determine higher requirements for image quality, resolution and field of view of the developed lens. In this case, the lens should be fast, thermally stabilized and have focus. The following lenses are considered: 4-lens with a focus of 50 mm, 3-lens with a focus of 150 mm and 7-lens with a variable focus of 30–150 mm.

Error analysis and optimal design of reduction relay lens for field of view stitching applications

Sensor Review ◽  
2021 ◽  
Vol 41 (1) ◽  
pp. 87-92
Author(s):  
Xinjie Zhang ◽  
Fansen Kong ◽  
Zhiyuan Gu ◽  
Xiao Shen
Keyword(s):  
Remote Sensing ◽  
Image Quality ◽  
High Accuracy ◽  
Structure Design ◽  
Reduction Ratio ◽  
Field Of View ◽  
Machining Accuracy ◽  
Optical Remote Sensing ◽  
Optical Elements ◽  
Content Type

Purpose FOV splicing optical remote sensing instruments have a strict requirement for the focal length consistency of the lens. In conventional optical-mechanical structure design, each optical element is equally distributed with high accuracy and everyone must have a high machining and assembly accuracy. For optical remote sensors with a large number of optical elements, this design brings great difficulties to lens manufacture and alignment. Design/methodology/approach Taking the relay lens in an optical remote sensing instrument with the field of view splicing as an example, errors of the system are redistributed to optical elements. Two optical elements, which have the greatest influence on modulation transfer function (MTF) of the system are mounted with high accuracy centering and the other elements are fixed by gland ring with common machining accuracy. The reduction ratio consistency difference among lenses is compensated by adjusting the optical spacing between the two elements. Findings Based on optical system simulation analysis, the optimized structure can compensate for the difference of reduction ratio among lens by grinding the washer thickness in the range of ±0.37 mm. The test data for the image quality of the lens show that the MTF value declined 0.043 within ±0.4 mm of space change between two barrels. The results indicate that the reduction ratio can be corrected by adjusting the washer thickness and the image quality will not obviously decline. Originality/value This paper confirms that this work is original and has not been published elsewhere nor is it currently under consideration for publication elsewhere. In this paper, the optimum structural design of the reduction relay lens for the field of view stitching applications is reported. The method of adjusting washer thickness is applied to compensate for the reduction ratio consistency difference of lenses. The optimized structure also greatly reduces the difficulty of lenses manufacture, alignment and improves the efficiency of assembly.

Evaluation of Image Quality According to Presence or Absence of Upper limbs in Scan Field of View During CT Examinations (Including LUNG MAN)

2017 ◽  
Vol 40 (4) ◽  
pp. 567-573
Author(s):  
Yuying Zhang ◽  
◽  
Haoyang Zheng ◽  
Kang-gyo Jung ◽  
Yu-Jin Cho ◽  
...  
Keyword(s):  
Image Quality ◽  
Field Of View ◽  
Upper Limbs

Apochromatic Collimator Objective Lens Design with Big Field of View

2013 ◽  
Vol 710 ◽  
pp. 413-418
Author(s):  
Fei Guo ◽  
Mei Zhao ◽  
Mai Yu Zhou ◽  
Ming Quan Yang ◽  
Shan Shan Cong
Keyword(s):  
Image Quality ◽  
Structural Parameters ◽  
Optical Design ◽  
Field Of View ◽  
Practical Significance ◽  
Large Field ◽  
Objective Lens ◽  
Initial Structure ◽  
Core Part

Objective lens is the core part of a collimator, its quality has a direct impact on the collimators quality. Due to the small field of view and low image quality requirement, general collimator objective lens is difficult to achieve the requirement of testing an aerial camera s performance. So designing a large field of view, apochromatic collimator objective lens has an important practical significance. In this paper, the major qualifications were first proposed to design the collimator objective lens,according to which the initial configuration was confirmed. Then we used the ZEMAX optical design software to optimize the initial structure and normalized the optimized structural parameters. Finally the image quality of collimator objective lens was evaluated to make it achieve the requirement of qualifications.

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