Dr. Daniel Shedlock Profile

Dr. Daniel Shedlock

Senior Scientist at Varex Imaging

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Publications (7)

Proceedings Article | 9 March 2017 Paper

1D pixelated MV portal imager with structured privacy film: a feasibility study

Pavlo Baturin, Daniel Shedlock, Marios Myronakis, Ross Berbeco, Josh Star-Lack

Proceedings Volume 10132, 1013240 (2017) https://doi.org/10.1117/12.2254606

KEYWORDS: Sensors, Photons, Gold, Spatial resolution, Reflection, Scintillators, Modulation transfer functions, Quantum efficiency, Optical filters, Radio optics, Imaging systems, Amorphous silicon, Electronic components, Electronic imaging

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Proceedings Article | 23 March 2015 Paper

Prototype 1.75 MV X-band linear accelerator testing for medical CT and industrial nondestructive testing applications

James Clayton, Daniel Shedlock, Steven Vanderet, George Zentai, Josh Star-Lack, Richard LaFave, Gary Virshup

Proceedings Volume 9438, 943813 (2015) https://doi.org/10.1117/12.2084394

KEYWORDS: Imaging systems, Prototyping, Nondestructive evaluation, X-rays, X-ray computed tomography, X band, Radiotherapy, Amorphous silicon, Metals, X-ray imaging

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Proceedings Article | 19 March 2014 Paper

Measurement of imaging properties of scintillating fiber optic plate

George Zentai, Arundhuti Ganguly, Josh Star-Lack, Gary Virshup, Hayley Hirsh, Daniel Shedlock, David Humber

Proceedings Volume 9033, 90333Q (2014) https://doi.org/10.1117/12.2043887

KEYWORDS: Modulation transfer functions, Imaging systems, X-rays, X-ray imaging, Fiber optics, Scintillators, Crystals, Fiber optics tests, Sensors, Copper

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Proceedings Article | 19 March 2014 Paper

Reflection properties of scintillator-septum candidates for a pixelated MeV detector

Mihye Shin, Josh Star-Lack, Martin Janecek, Eric Abel, Daniel Shedlock, Rebecca Fahrig

Proceedings Volume 9033, 90331H (2014) https://doi.org/10.1117/12.2043281

KEYWORDS: Sensors, Reflectivity, Reflection, Interfaces, Reflectors, Glasses, Scintillators, Surface finishing, Optical properties, Polishing

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Proceedings Article | 24 September 2007 Paper

An adapted modulation transfer function for x-ray backscatter radiography by selective detection

Nissia Sabri, Edward Dugan, Alan Jacobs, Daniel Shedlock

Proceedings Volume 6706, 670614 (2007) https://doi.org/10.1117/12.739070

KEYWORDS: Modulation transfer functions, Fourier transforms, Imaging systems, Image quality, X-rays, Radiography, Point spread functions, Sensors, X-ray imaging, Backscatter

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Proceedings Article | 17 September 2005 Paper

Optimization of an RSD x-ray backscatter system for detecting defects in the space shuttle external tank thermal foam insulation

Daniel Shedlock, Benjamin Addicott, Edward Dugan, Alan Jacobs

Proceedings Volume 5923, 59230S (2005) https://doi.org/10.1117/12.618591

KEYWORDS: Sensors, X-rays, Foam, Backscatter, Collimators, Aluminum, X-ray detectors, X-ray imaging, Defect detection, Monte Carlo methods

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A new Compton x-ray backscatter imaging technique, backscatter radiography by selective detection (RSD), has been used for inspection of the spray-on-foam-insulation (SOFI) on the space shuttle external tank. RSD employs detection of selected backscatter field components, by using specially designed detectors with movable detector collimators, to achieve high image contrast. The optimization study utilized test panels with simulated and natural defects in the spray-on foam insulation. Some of the test panels include structural features, stiffener-stringers and connection flanges, which were bolted to an aluminum base plate representative of the external tank. The SOFI was then layed down over the base plate and structural components with thicknesses varying from a few tens of mm up to a few hundred mm. The simulated defects range in cross-sectional size from 6 × 6 mm to 50 × 50 mm. Natural defects including roll-over voids and knit-line delaminations have a wide range of sizes, geometries, and orientations with a minimum critical cross-sectional size of 6 mm. Imaging registration is currently obtained at 0.05 seconds per 2 mm pixel, or about 19 minutes per 0.093 m²(1 ft²). The current system is being evaluated to enhance the detection of natural defects of a minimal critical size. Monte Carlo (MC) simulations with MCNP5 are being used to determine the history and corresponding spectrum of the detected photons that are responsible for improving defect image contrast. The simulation results are used in combination with experimental data to select optimal detector configurations. Detector configurations are sensitive not only to the type of defect being detected, but also the defect's depth in SOFI, distance from aluminum substrate, and defect orientation. Additional parameters including detector type, detection mode, and x-ray illumination beam size were also evaluated. Both NaI and plastic (BC404) scintillation detectors in pulse and integral mode were used to determine their effect on image quality and defect detection sensitivity. The x-ray illumination beam geometry (round versus square) and beam spot size were varied to determine resolution and the effect on defect contrast. The current system using pulse mode NaI detectors, and a 2 mm round x-ray illumination beam can detect the presence of the smallest critical size defects at a scan rate of 0.05 seconds per 2 mm pixel.

Proceedings Article | 26 October 2004 Paper

Detection of defects in foam thermal insulation using lateral migration backscatter x-ray radiography

Edward Dugan, Alan Jacobs, Dan Shedlock, Dan Ekdahl

Proceedings Volume 5541, (2004) https://doi.org/10.1117/12.559719

KEYWORDS: Sensors, Foam, Collimators, X-rays, Radiography, Backscatter, Aluminum, Defect detection, X-ray imaging, Mouth

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