Dr. Andrew G. Davies Profile

Dr. Andrew G. Davies

Lecturer at Univ of Leeds

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Author

Publications (20)

Proceedings Article | 3 April 2023 Presentation + Paper

A visibility overshoot index for interventional x-ray image quality assessment

Asli Kumcu, Ljiljana Platiša, Bart Goossens, Amber Gislason-Lee, Andrew Davies, Gerard Schouten, Dimitri Buytaert, Klaus Bacher, Wilfried Philips

Proceedings Volume 12467, 124670T (2023) https://doi.org/10.1117/12.2652548

KEYWORDS: Signal detection, X-rays, Visualization, Visibility, Visual process modeling, X-ray imaging, Image quality, Dose control

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Proceedings Article | 8 July 2021 Presentation + Paper

Sub-surface damage detection in marble structures using THz time domain and laser feedback interferometric imaging

Aparajita Bandyopadhyay, Karl Bertling, Diksha Garg, Khushboo Singh, Tim Gillespie, Yah Leng Lim, Lianhe Li, Paul Dean, Dragan Indjin, Edmund Linfield, A. Giles Davies, Aleksandar Rakic, Amartya Sengupta

Proceedings Volume 11784, 117840T (2021) https://doi.org/10.1117/12.2592548

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SPIE Journal Paper | 2 May 2017

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

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

JMI, Vol. 4, Issue 02, 025501, (May 2017) https://doi.org/10.1117/12.10.1117/1.JMI.4.2.025501

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 | 27 October 2015

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

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

JEI, Vol. 24, Issue 05, 051006, (October 2015) https://doi.org/10.1117/12.10.1117/1.JEI.24.5.051006

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 | 21 September 2015

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

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

JEI, Vol. 24, Issue 05, 051002, (September 2015) https://doi.org/10.1117/12.10.1117/1.JEI.24.5.051002

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 | 16 March 2015 Paper

Image quality based x-ray dose control in cardiac imaging

Andrew Davies, Stephen Kengyelics, Amber Gislason-Lee

Proceedings Volume 9399, 93990E (2015) https://doi.org/10.1117/12.2082795

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

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Proceedings Article | 16 March 2015 Paper

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

Asli Kumcu, Ljiljana Platiša, Heng Chen, Amber Gislason-Lee, Andrew Davies, Peter Schelkens, Yves Taeymans, Wilfried Philips

Proceedings Volume 9399, 93990F (2015) https://doi.org/10.1117/12.2083431

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

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Proceedings Article | 16 March 2015 Paper

Machine vision image quality measurement in cardiac x-ray imaging

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

Proceedings Volume 9399, 93990J (2015) https://doi.org/10.1117/12.2083208

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

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Proceedings Article | 16 March 2015 Paper

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

Amber Gislason-Lee, Asli Kumcu, Stephen Kengyelics, Laura Rhodes, Andrew Davies

Proceedings Volume 9399, 93990L (2015) https://doi.org/10.1117/12.2082788

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

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Proceedings Article | 20 April 2005 Paper

Effect of flare on computed radiography systems

John Rowlands, Stephen Kengyelics, Andrew Davies, Winston Ji, Kuo Yan

Proceedings Volume 5745, (2005) https://doi.org/10.1117/12.597382

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

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Proceedings Article | 5 June 2003 Paper

Image quality of digital radiography using flat detector technology

Thierry Ducourant, David Couder, Thibaut Wirth, J. Trochet, Raoul Bastiaens, Tom Bruijns, Hans Luijendijk, Bernhard Sandkamp, Andrew Davies, Dominique Didier, Agustin Gonzalez, Sylvain Terraz, Daniel Ruefenacht

Proceedings Volume 5030, (2003) https://doi.org/10.1117/12.479969

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

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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 | 3 May 2002 Paper

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

Tom Bruijns, Raoul Bastiaens, Bart Hoornaert, Eric von Reth, Falko Busse, Volker Heer, Thierry Ducourant, Arnold Cowen, Andrew Davies, Francois Terrier

Proceedings Volume 4682, (2002) https://doi.org/10.1117/12.465574

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

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Proceedings Article | 25 April 2000 Paper

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

Tom Bruijns, Thijs Adriaansz, Arnold Cowen, Andrew Davies, Stephen Kengyelics, Kourosh Kiani, Han Kroon, Hans Luijendijk

Proceedings Volume 3977, (2000) https://doi.org/10.1117/12.384484

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

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Proceedings Article | 28 May 1999 Paper

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

Tom Bruijns, Robert Bury, Falko Busse, Andrew Davies, Arnold Cowen, Walter Ruetten, Hans Reitsma

Proceedings Volume 3659, (1999) https://doi.org/10.1117/12.349507

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

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Proceedings Article | 28 May 1999 Paper

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

Stephen Kengyelics, Arnold Cowen, Andrew Davies

Proceedings Volume 3659, (1999) https://doi.org/10.1117/12.349494

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

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Proceedings Article | 24 May 1999 Paper

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

Andrew Davies, Arnold Cowen, Tom Bruijns

Proceedings Volume 3663, (1999) https://doi.org/10.1117/12.349639

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

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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 | 15 April 1996 Paper

Spatial resolution requirements for soft-copy reporting in digital radiography

Andrew Davies, Arnold Cowen, Richard Fowler, Robert Bury, Geoff Parkin, David Lintott, Delia Martinez, Asif Safudim

Proceedings Volume 2707, (1996) https://doi.org/10.1117/12.238461

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

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Proceedings Article | 15 April 1996 Paper

First experiences with a dry digital laser imager for computed radiography

Arnold Cowen, Andrew Davies, Stephen Kengyelics, Edmund Baker, Gavin McLeod, Geoff Parkin

Proceedings Volume 2707, (1996) https://doi.org/10.1117/12.238480

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

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Proceedings Article | 27 March 1996 Paper

Optimizing the processing and presentation of PPCR imaging

Andrew Davies, Arnold Cowen, Geoff Parkin, Robert Bury

Proceedings Volume 2712, (1996) https://doi.org/10.1117/12.236857

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

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Proceedings Article | 14 September 1993 Paper

An image processing algorithm for PPCR imaging

Arnold Cowen, Anthony Giles, Andrew Davies, A. Workman

Proceedings Volume 1898, (1993) https://doi.org/10.1117/12.154569

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

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