Mr. Andrew G. Davies Profile

Mr. Andrew G. Davies

at Univ of Leeds

SPIE Involvement:

Author

Publications (18)

SPIE Journal Paper | May 2, 2017

Comprehensive assessment of patient image quality and radiation dose in latest generation cardiac x-ray equipment for percutaneous coronary interventions

Gislason-Lee, Amber , Keeble, Claire , Egleston, Daniel , Bexon, Josephine , Kengyelics, Stephen , Davies, Andrew

JMI Vol. 4 Issue 02

KEYWORDS: Image quality, X-rays, X-ray imaging, Angiography, Fluoroscopy, Imaging systems, Image enhancement, Medical imaging, Medicine, Light sources and illumination

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SPIE Journal Paper | October 27, 2015

How much image noise can be added in cardiac x-ray imaging without loss in perceived image quality?

Gislason-Lee, Amber , Kumcu, Asli , Kengyelics, Stephen , Brettle, David , Treadgold, Laura , Sivananthan, Mohan , Davies, Andrew

JEI Vol. 24 Issue 05

KEYWORDS: X-ray imaging, Image quality, X-rays, Angiography, Signal to noise ratio, Calibration, Image processing, Image enhancement, Sensors, Arteries

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SPIE Journal Paper | September 21, 2015

Context sensitive cardiac x-ray imaging: a machine vision approach to x-ray dose control

Kengyelics, Stephen , Gislason-Lee, Amber , Keeble, Claire , Magee, Derek , Davies, Andrew

JEI Vol. 24 Issue 05

KEYWORDS: X-ray imaging, Signal attenuation, X-rays, Machine vision, Control systems, Arteries, Imaging systems, Algorithm development, Blood vessels, Sensors

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PROCEEDINGS ARTICLE | March 16, 2015

Machine vision image quality measurement in cardiac x-ray imaging

Proc. SPIE. 9399, Image Processing: Algorithms and Systems XIII

KEYWORDS: Imaging systems, X-rays, Arteries, Image quality, Iodine, Machine vision, Algorithm development, X-ray imaging, Signal detection, Binary data

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PROCEEDINGS ARTICLE | March 16, 2015

How much image noise can be added in cardiac x-ray imaging without loss in perceived image quality?

Proc. SPIE. 9399, Image Processing: Algorithms and Systems XIII

KEYWORDS: Imaging systems, Image processing, X-rays, Heart, Control systems, Medical imaging, Image quality, Angiography, Image enhancement, X-ray imaging

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PROCEEDINGS ARTICLE | March 16, 2015

Image quality based x-ray dose control in cardiac imaging

Proc. SPIE. 9399, Image Processing: Algorithms and Systems XIII

KEYWORDS: Polymethylmethacrylate, Imaging systems, Signal attenuation, X-rays, Control systems, Computer simulations, Arteries, Image quality, Receptors, X-ray imaging

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PROCEEDINGS ARTICLE | March 16, 2015

Selecting stimuli parameters for video quality assessment studies based on perceptual similarity distances

Proc. SPIE. 9399, Image Processing: Algorithms and Systems XIII

KEYWORDS: Surgery, Image processing, Video, X-rays, Image quality, Video compression, Picosecond phenomena, Laparoscopy, Visibility, Image quality standards

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PROCEEDINGS ARTICLE | April 20, 2005

Effect of flare on computed radiography systems

Proc. SPIE. 5745, Medical Imaging 2005: Physics of Medical Imaging

KEYWORDS: Waveguides, Scanners, Photons, X-rays, Light scattering, Radiography, Computing systems, Chromium, Modulation transfer functions, X-ray imaging

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PROCEEDINGS ARTICLE | June 5, 2003

Image quality of digital radiography using flat detector technology

Proc. SPIE. 5030, Medical Imaging 2003: Physics of Medical Imaging

KEYWORDS: Switching, Sensors, X-rays, Photodiodes, Bone, Image quality, Angiography, Modulation transfer functions, Fluoroscopy, Visibility

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One of the most demanding applications in dynamic X-Ray imaging is Digital Subtraction Angiography (DSA). As opposed to other applications such as Radiography or Fluoroscopy, there has been so far limited attempts to introduce DSA with flat detector (FD) technology: Up to now, only part of the very demanding requirements could be taken into account. In order to enable an introduction of FD technology also in this area, a complete understanding of all physical phenomena related to the use of this technology in DSA is necessary. This knowledge can be used for detector design and performance optimization. Areas of research include fast switching between several detector operating modes (e.g. switching between fluoroscopy and high dose exposure modes and vice versa) and non stability during the DSA run e.g. due to differences in gain between subsequent images. Furthermore, effects of local and global X-Ray overexposure (due to direct radiation), which can cause temporal artifacts such as ghosting, may have a negative impact on the image quality. Pixel shift operations and image subtraction enhance the visibility of any artifact. The use of a refresh light plays an important role in the optimization process. Both an 18x18 cm² as well as a large area 30x40 cm² flat panel detector are used for studying the various phenomena. Technical measurements were obtained using complex imaging sequences representing the most demanding application conditions. Studies on subtraction test objects were performed and vascular applications have been carried out in order to confirm earlier findings. The basis for comparison of DSA is, still, the existing and mature IITV technology. The results of this investigation show that the latest generation of dynamic flat detectors is capable of handling this kind of demanding application. Not only the risk areas and their solutions and points of attention will be addressed, but also the benefits of present FD technology with respect to state-of-the-art IITV technology regarding DSA will be discussed.

PROCEEDINGS ARTICLE | May 3, 2002

Image quality of a large-area dynamic flat detector: comparison with a state-of-the-art II/TV system

Proc. SPIE. 4682, Medical Imaging 2002: Physics of Medical Imaging

KEYWORDS: Imaging systems, Sensors, X-rays, Radiography, CCD cameras, Image quality, Image intensifiers, Modulation transfer functions, Fluoroscopy, X-ray imaging

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PROCEEDINGS ARTICLE | April 25, 2000

Simulation of the image quality of an a-Si flat x-ray detector system in low-dose fluoroscopic applications

Proc. SPIE. 3977, Medical Imaging 2000: Physics of Medical Imaging

KEYWORDS: Signal to noise ratio, Imaging systems, Sensors, Calibration, X-rays, Interference (communication), Image quality, Fluoroscopy, X-ray imaging, X-ray detectors

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One of the issues in (alpha) -Si:H X-ray detectors is signal to noise ratio for low dose fluoroscopic applications. An optimized sensitivity of the X-ray detection system together with low and isotropic system noise characteristics are primary pre-conditions needed for maximum image quality. However, in spite of high DQE numbers of this Flat Detector technology in radiological and fluoroscopic application areas, a SNR for low dose fluoroscopy is found, which is inferior to that found with Image Intensifier-TV based systems. The problem area is a small dose range, producing gray levels just above absolute dark. Except for the dark level, these levels can (dependent on the application area) contain clinically relevant information. Since scatter affects the darker parts of the relevant image areas there will be noise in those areas, caused by X-ray quantum statistics and readout noise. The objective of the simulations is to investigate the influence of the various system noise components on the image quality. A level of system noise can be found where the subjective image quality is mainly determined by the X-ray quantum statistics and where the readout noise does not necessarily have to be invisible in totally dark parts. The simulation concerns a threshold contrast detail detectability (TCDD) observation test, where observers score discs of various diameter and absorption in an image sequence (being a fixed scene of the test object with (temporal) X-ray noise and system noise). The dynamic sequence is based upon total simulation, i.e. the test object as well as the X-ray noise and the system noise components were simulated. To verify the simulations also an image sequence was acquired on a Flat Detector system. The observations are done at various dose levels, with and without post processing to obtain noise reduction like it is used in clinical practice for this kind of system. The sequences are observed on a medical CRT display.

PROCEEDINGS ARTICLE | May 28, 1999

Technical and clinical assessments of an experimental flat dynamic x-ray image detector system

Proc. SPIE. 3659, Medical Imaging 1999: Physics of Medical Imaging

KEYWORDS: Signal to noise ratio, Imaging systems, Spatial frequencies, Sensors, X-rays, Image quality, Image enhancement, Fluoroscopy, X-ray imaging, X-ray detectors

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PROCEEDINGS ARTICLE | May 28, 1999

Image quality evaluation of a direct digital radiography detector operating in a UK radiology department

Proc. SPIE. 3659, Medical Imaging 1999: Physics of Medical Imaging

KEYWORDS: Imaging systems, Spatial frequencies, Sensors, Image processing, Photons, X-rays, Radiography, Chromium, Image quality, X-ray imaging

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PROCEEDINGS ARTICLE | May 24, 1999

Psychophysical evaluation of the image quality of a dynamic flat-panel digital x-ray image detector using the threshold contrast detail detectability (TCDD) technique

Proc. SPIE. 3663, Medical Imaging 1999: Image Perception and Performance

KEYWORDS: Imaging systems, Cameras, Sensors, Image processing, Denoising, X-rays, Image quality, Fluoroscopy, X-ray imaging, X-ray detectors

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We are currently in an era of active development of the digital X-ray imaging detectors that will serve the radiological communities in the new millennium. The rigorous comparative physical evaluations of such devices are therefore becoming increasingly important from both the technical and clinical perspectives. The authors have been actively involved in the evaluation of a clinical demonstration version of a flat-panel dynamic digital X-ray image detector (or FDXD). Results of objective physical evaluation of this device have been presented elsewhere at this conference. The imaging performance of FDXD under radiographic exposure conditions have been previously reported, and in this paper a psychophysical evaluation of the FDXD detector operating under continuous fluoroscopic conditions is presented. The evaluation technique employed was the threshold contrast detail detectability (TCDD) technique, which enables image quality to be measured on devices operating in the clinical environment. This approach addresses image quality in the context of both the image acquisition and display processes, and uses human observers to measure performance. The Leeds test objects TO[10] and TO[10+] were used to obtain comparative measurements of performance on the FDXD and two digital spot fluorography (DSF) systems, one utilizing a Plumbicon camera and the other a state of the art CCD camera. Measurements were taken at a range of detector entrance exposure rates, namely 6, 12, 25 and 50 (mu) R/s. In order to facilitate comparisons between the systems, all fluoroscopic image processing such as noise reduction algorithms, were disabled during the experiments. At the highest dose rate FDXD significantly outperformed the DSF comparison systems in the TCDD comparisons. At 25 and 12 (mu) R/s all three-systems performed in an equivalent manner and at the lowest exposure rate FDXD was inferior to the two DSF systems. At standard fluoroscopic exposures, FDXD performed in an equivalent manner to the DSF systems for the TCDD comparisons. This would suggest that FDXD would therefore perform adequately in a clinical fluoroscopic environment and our initial clinical experiences support this. Noise reduction processing of the fluoroscopic data acquired on FDXD was also found to further improve TCDD performance for FDXD. FDXD therefore combines acceptable fluoroscopic performance with excellent radiographic (snap shot) imaging fidelity, allowing the possibility of a universal x-ray detector to be developed, based on FDXD's technology. It is also envisaged that fluoroscopic performance will be improved by the development of digital image enhancement techniques specifically tailored to the characteristics of the FDXD detector.

PROCEEDINGS ARTICLE | April 15, 1996

Spatial resolution requirements for soft-copy reporting in digital radiography

Proc. SPIE. 2707, Medical Imaging 1996: Image Display

KEYWORDS: Imaging systems, Image processing, Radiography, Diagnostics, Image resolution, Chromium, Bone, Image quality, Image enhancement, Spatial resolution

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PROCEEDINGS ARTICLE | April 15, 1996

First experiences with a dry digital laser imager for computed radiography

Proc. SPIE. 2707, Medical Imaging 1996: Image Display

KEYWORDS: Imaging systems, Spatial frequencies, Image processing, Error analysis, Radiography, Diagnostics, Printing, Image quality, Laser systems engineering, Clinical trials

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PROCEEDINGS ARTICLE | March 27, 1996

Optimizing the processing and presentation of PPCR imaging

Proc. SPIE. 2712, Medical Imaging 1996: Image Perception

KEYWORDS: Chest, Imaging systems, Image processing, Radiography, Diagnostics, Chromium, Lung, Mammography, Image enhancement, Algorithm development

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PROCEEDINGS ARTICLE | September 14, 1993

An image processing algorithm for PPCR imaging

Proc. SPIE. 1898, Medical Imaging 1993: Image Processing

KEYWORDS: Chest, Image processing, Radiography, Computing systems, Diagnostics, Chromium, Image quality, Image enhancement, Algorithm development, Image quality standards

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Showing 5 of 18 publications

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