Dr. William A. Worstell Profile

Dr. William A. Worstell

Research Scientist

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Publications (6)

Proceedings Article | 1 March 2019 Presentation + Paper

First results developing time-of-flight proton radiography for proton therapy applications

William Worstell, Bernhard Adams, Melvin Aviles, Justin Bond, Ethan Cascio, Till Cremer, Georges El Fakhri, Camden Ertley, Michael Foley, Kira Grogg, Cole Hamel, Hsiao-Ming Lu, Alexey Lyashenko, Michael Minot, Harald Paganetti, Mark Popecki, Michael Stochaj

Proceedings Volume 10948, 109480G (2019) https://doi.org/10.1117/12.2511804

KEYWORDS: Sensors, Microchannel plates, Radiography, Telescopes, Picosecond phenomena, Photodetectors, Oscilloscopes, Quantum efficiency, Resistance, Pulsed laser operation

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Proceedings Article | 19 September 2017 Presentation

Life testing of ALD-GCA MCPs: recent results (Conference Presentation)

Mark Popecki, Christopher Craven, Till Cremer, William Worstell, Michael Minot, Bernhard Adams, Michael Foley, Alexey Lyashenko, Justin Bond, Michael Stochaj, Camden Ertley, Oswald H. Siegmund, Jeffrey Elam, Anil Mane

Proceedings Volume 10397, 103970Y (2017) https://doi.org/10.1117/12.2277365

KEYWORDS: Microchannel plates, Resistance, Atomic layer deposition, Glasses, Thin films, Tolerancing, Manufacturing, Photodiodes

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Proceedings Article | 19 September 2017 Presentation

ALD-microchannel plates for cryogenic applications (Conference Presentation)

Till Cremer, Bernhard Adams, Melvin Aviles, Justin Bond, Christopher Craven, Michael Foley, Alexey Lyashenko, Michael Minot, Mark Popecki, Michael Stochaj, William Worstell, Jeffrey Elam, Anil Mane, Oswald H. Siegmund, Camden Ertley

Proceedings Volume 10397, 103970Z (2017) https://doi.org/10.1117/12.2277185

KEYWORDS: Microchannel plates, Resistance, Cryogenics, Atomic layer deposition, Glasses, Manufacturing, Semiconductors, Temperature metrology, Nanostructures

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Proceedings Article | 30 September 2016 Presentation + Paper

Pilot production and advanced development of large-area picosecond photodetectors

Michael Minot, Bernhard Adams, Melvin Aviles, Justin Bond, Christopher Craven, Till Cremer, Michael Foley, Alexey Lyashenko, Mark Popecki, Michael Stochaj, William Worstell, Anil Mane, Jeffrey Elam, Oswald H. Siegmund, Camden Ertley, Henry Frisch, Andrey Elagin

Proceedings Volume 9968, 99680X (2016) https://doi.org/10.1117/12.2237331

KEYWORDS: Microchannel plates, Picosecond phenomena, Photodetectors, Atomic layer deposition, Sensors, Ceramics, Resistance, Glasses, Quantum efficiency, Indium

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We report pilot production and advanced development performance results achieved for Large Area Picosecond Photodetectors (LAPPD). The LAPPD is a microchannel plate (MCP) based photodetector, capable of imaging with single-photon sensitivity at high spatial and temporal resolutions in a hermetic package with an active area of 400 square centimeters. In December 2015, Incom Inc. completed installation of equipment and facilities for demonstration of early stage pilot production of LAPPD. Initial fabrication trials commenced in January 2016. The “baseline” LAPPD employs an all-glass hermetic package with top and bottom plates and sidewalls made of borosilicate float glass. Signals are generated by a bi-alkali Na₂KSb photocathode and amplified with a stacked chevron pair of “next generation” MCPs produced by applying resistive and emissive atomic layer deposition coatings to borosilicate glass capillary array (GCA) substrates. Signals are collected on RF strip-line anodes applied to the bottom plates which exit the detector via pinfree hermetic seals under the side walls. Prior tests show that LAPPDs have electron gains greater than 107, submillimeter space resolution for large pulses and several mm for single photons, time resolutions of 50 picoseconds for single photons, predicted resolution of less than 5 picoseconds for large pulses, high stability versus charge extraction, and good uniformity. LAPPD performance results for product produced during the first half of 2016 will be reviewed. Recent advances in the development of LAPPD will also be reviewed, as the baseline design is adapted to meet the requirements for a wide range of emerging application. These include a novel ceramic package design, ALD coated MCPs optimized to have a low temperature coefficient of resistance (TCR) and further advances to adapt the LAPPD for cryogenic applications using Liquid Argon (LAr). These developments will meet the needs for DOE-supported RD for the Deep Underground Neutrino Experiment (DUNE), nuclear physics applications such as EIC, medical, homeland security and astronomical applications for direct and indirect photon detection.

SPIE Journal Paper | 12 July 2016

Numerical observer for atherosclerotic plaque classification in spectral computed tomography

Auranuch Lorsakul, Georges El Fakhri, William Worstell, Jinsong Ouyang, Yothin Rakvongthai, Andrew Laine, Quanzheng Li

JMI, Vol. 3, Issue 03, 035501, (July 2016) https://doi.org/10.1117/12.10.1117/1.JMI.3.3.035501

KEYWORDS: Computed tomography, Signal attenuation, Signal to noise ratio, Sensors, Image filtering, X-ray computed tomography, Arteries, Imaging systems, X-rays, Medical imaging

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Spectral computed tomography (SCT) generates better image quality than conventional computed tomography (CT). It has overcome several limitations for imaging atherosclerotic plaque. However, the literature evaluating the performance of SCT based on objective image assessment is very limited for the task of discriminating plaques. We developed a numerical-observer method and used it to assess performance on discrimination vulnerable-plaque features and compared the performance among multienergy CT (MECT), dual-energy CT (DECT), and conventional CT methods. Our numerical observer was designed to incorporate all spectral information and comprised two-processing stages. First, each energy-window domain was preprocessed by a set of localized channelized Hotelling observers (CHO). In this step, the spectral image in each energy bin was decorrelated using localized prewhitening and matched filtering with a set of Laguerre–Gaussian channel functions. Second, the series of the intermediate scores computed from all the CHOs were integrated by a Hotelling observer with an additional prewhitening and matched filter. The overall signal-to-noise ratio (SNR) and the area under the receiver operating characteristic curve (AUC) were obtained, yielding an overall discrimination performance metric. The performance of our new observer was evaluated for the particular binary classification task of differentiating between alternative plaque characterizations in carotid arteries. A clinically realistic model of signal variability was also included in our simulation of the discrimination tasks. The inclusion of signal variation is a key to applying the proposed observer method to spectral CT data. Hence, the task-based approaches based on the signal-known-exactly/background-known-exactly (SKE/BKE) framework and the clinical-relevant signal-known-statistically/background-known-exactly (SKS/BKE) framework were applied for analytical computation of figures of merit (FOM). Simulated data of a carotid-atherosclerosis patient were used to validate our methods. We used an extended cardiac-torso anthropomorphic digital phantom and three simulated plaque types (i.e., calcified plaque, fatty-mixed plaque, and iodine-mixed blood). The images were reconstructed using a standard filtered backprojection (FBP) algorithm for all the acquisition methods and were applied to perform two different discrimination tasks of: (1) calcified plaque versus fatty-mixed plaque and (2) calcified plaque versus iodine-mixed blood. MECT outperformed DECT and conventional CT systems for all cases of the SKE/BKE and SKS/BKE tasks (all p<0.01). On average of signal variability, MECT yielded the SNR improvements over other acquisition methods in the range of 46.8% to 65.3% (all p<0.01) for FBP-Ramp images and 53.2% to 67.7% (all p<0.01) for FBP-Hanning images for both identification tasks. This proposed numerical observer combined with our signal variability framework is promising for assessing material characterization obtained through the additional energy-dependent attenuation information of SCT. These methods can be further extended to other clinical tasks such as kidney or urinary stone identification applications.

Proceedings Article | 19 March 2014 Paper

A spectral CT technique using balanced K-edge filter set

Yothin Rakvongthai, William Worstell, Georges El Fakhri, Jinsong Ouyang

Proceedings Volume 9033, 90335M (2014) https://doi.org/10.1117/12.2043747

KEYWORDS: Optical filters, Signal attenuation, Spectroscopy, Data acquisition, X-rays, Computed tomography, Image filtering, Cerium, Dysprosium, Silver

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