Dr. Steven W. Tilley Profile

Dr. Steven W. Tilley

Imaging Analyst

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Publications (10)

Proceedings Article | 28 May 2019 Paper

Optimized spatial-spectral CT for multi-material decomposition

Matthew Tivnan, Wenying Wang, Steven Tilley, Jeffrey Siewerdsen, J. Stayman

Proceedings Volume 11072, 1107211 (2019) https://doi.org/10.1117/12.2534333

KEYWORDS: Optical filters, Linear filtering, Image filtering, Sensors, Model-based design, X-ray computed tomography, Imaging systems, Gold, Nonlinear filtering, Data acquisition

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Proceedings Article | 28 May 2019 Paper

Known-component model-based material decomposition for dual energy imaging of bone compositions in the presence of metal implant

S. Liu, S. Tilley, Q. Cao, J. Siewerdsen, J. Stayman, W. Zbijewski

Proceedings Volume 11072, 1107213 (2019) https://doi.org/10.1117/12.2534725

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Dual energy computed tomography (DE CT) is a promising technology for the assessment of bone compositions. One of potential applications involves evaluations of fracture healing using longitudinal measurements of callus mineralization. However, imaging of fractures is often challenged by the presence of metal fixation hardware. In this work, we report on a new simultaneous DE reconstruction-decomposition algorithm that integrates the previously introduced Model-Based Material Decomposition (MBMD) with a Known-Component (KC) framework to mitigate metal artifacts. The algorithm was applied to the DE data obtained on a dedicated extremity cone-beam CT (CBCT) with capability for weight-bearing imaging. To acquire DE projections in a single gantry rotation, we exploited a unique multisource design of the system, where three X-ray sources were mounted parallel to the axis of rotation. The central source provided high energy (HE) data at 120 kVp, while the two remaining sources were operated at a low energy (LE) of 60 kVp. This novel acquisition trajectory further motivates the use of MBMD to accommodate this complex DE sampling pattern. The algorithm was validated in a simulation study using a digital extremity phantom. The phantom consisted of a water background with an insert containing varying concentrations of calcium (50 – 175 mg/mL). Two configurations of titanium implants were considered: a fixation plate and an intramedullary nail. The accuracy of calcium-water decompositions obtained with the proposed KC-MBMD algorithm was compared to MBMD without metal component model. Metal artifacts were almost completely removed by KC-MBMD. Relative absolute errors of calcium concentration in the vicinity of metal were 6% - 31% for KC-MBMD (depending on the calcium insert and implant configuration), compared favorably to 48% - 273% for MBMD. Moreover, accuracy of concentration estimates for KC-MBMD in the presence of metal implant approached that of MBMD in a configuration without implant (6%-23%). The proposed algorithm achieved accurate DE material decomposition in the presence of metal implants using a non-conventional, axial multisource DE acquisition pattern.

Proceedings Article | 28 May 2019 Paper

Local response prediction in model-based CT material decomposition

Wenying Wang, Steven Tilley, Matthew Tivnan, J. Webster Stayman

Proceedings Volume 11072, 110720Z (2019) https://doi.org/10.1117/12.2534437

KEYWORDS: Point spread functions, Model-based design, X-ray computed tomography, Image quality, Spectral computed tomography

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Proceedings Article | 4 March 2019 Presentation

Robust photometric stereo endoscopy via deep learning trained on synthetic data (Conference Presentation)

Faisal Mahmood, Daniel Borders, Richard Chen, Jordan Sweer, Steven Tilley, Norman Nishioka, J. Webster Stayman, Nicholas Durr

Proceedings Volume 10871, 108710N (2019) https://doi.org/10.1117/12.2509878

KEYWORDS: Endoscopy, Colorectal cancer, Endoscopes, Data modeling, 3D modeling, Colon, Light sources, Error analysis, Cancer, Cameras

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Proceedings Article | 1 March 2019 Presentation + Paper

Physical modeling and performance of spatial-spectral filters for CT material decomposition

Matthew Tivnan, Steven Tilley, J. Stayman

Proceedings Volume 10948, 109481A (2019) https://doi.org/10.1117/12.2513481

KEYWORDS: Sensors, Motion models, Performance modeling, Iodine, Data modeling, Gold, X-rays, Detection and tracking algorithms, Reconstruction algorithms

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Proceedings Article | 9 March 2018 Presentation + Paper

High-resolution extremity cone-beam CT with a CMOS detector: evaluation of a clinical prototype in quantitative assessment of bone microarchitecture

Q. Cao, M. Brehler, A. Sisniega, S. Tilley, M. Shiraz Bhurwani, J. Stayman, J. Yorkston, J. Siewerdsen, W. Zbijewski

Proceedings Volume 10573, 105730R (2018) https://doi.org/10.1117/12.2293810

KEYWORDS: Bone, CMOS sensors, Image segmentation, Prototyping, Sensors, Scanners, Modulation transfer functions, Imaging systems, Amorphous silicon, Scintillators

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Purpose: A prototype high-resolution extremity cone-beam CT (CBCT) system based on a CMOS detector was developed to support quantitative in vivo assessment of bone microarchitecture. We compare the performance of CMOS CBCT to an amorphous silicon (a-Si:H) FPD extremity CBCT in imaging of trabecular bone.

Methods: The prototype CMOS-based CBCT involves a DALSA Xineos3030 detector (99 μm pixels) with 400 μm-thick CsI scintillator and a compact 0.3 FS rotating anode x-ray source. We compare the performance of CMOS CBCT to an a- Si:H FPD scanner built on a similar gantry, but using a Varian PaxScan2530 detector with 0.137 mm pixels and a 0.5 FS stationary anode x-ray source. Experimental studies include measurements of Modulation Transfer Function (MTF) for the detectors and in 3D image reconstructions. Image quality in clinical scenarios is evaluated in scans of a cadaver ankle. Metrics of trabecular microarchitecture (BV/TV, Bone Volume/Total Volume, TbSp, Trabecular Spacing, and TbTh, trabecular thickness) are obtained in a human ulna using CMOS CBCT and a-Si:H FPD CBCT and compared to gold standard μCT.

Results: The CMOS detector achieves ~40% increase in the f20 value (frequency at which MTF reduces to 0.20) compared to the a-Si:H FPD. In the reconstruction domain, the FWHM of a 127 μm tungsten wire is also improved by ~40%. Reconstructions of a cadaveric ankle reveal enhanced modulation of trabecular structures with the CMOS detector and soft-tissue visibility that is similar to that of the a-Si:H FPD system. Correlations of the metrics of bone microarchitecture with gold-standard μCT are improved with CMOS CBCT: from 0.93 to 0.98 for BV/TV, from 0.49 to 0.74 for TbTh, and from 0.9 to 0.96 for TbSp.

Conclusion: Adoption of a CMOS detector in extremity CBCT improved spatial resolution and enhanced performance in metrics of bone microarchitecture compared to a conventional a-Si:H FPD. The results support development of clinical applications of CMOS CBCT in quantitative imaging of bone health.

Proceedings Article | 9 March 2018 Presentation + Paper

A general CT reconstruction algorithm for model-based material decomposition

Steven Tilley, Wojciech Zbijewski, Jeffrey Siewerdsen, J. Webster Stayman

Proceedings Volume 10573, 105731E (2018) https://doi.org/10.1117/12.2293776

KEYWORDS: Calcium, Switching, X-rays, Reconstruction algorithms, Model-based design, Data modeling, Sensors, CT reconstruction, X-ray detectors

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Proceedings Article | 9 March 2017 Presentation + Paper

Deformable known component model-based reconstruction for coronary CT angiography

X. Zhang, S. Tilley, S. Xu, A. Mathews, E. McVeigh, J. Stayman

Proceedings Volume 10132, 1013213 (2017) https://doi.org/10.1117/12.2255303

KEYWORDS: Metals, Lead, Model-based design, Arteries, CT reconstruction, Electrodes, Heart, Signal attenuation, Optical spheres, X-rays, Copper

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Proceedings Article | 22 March 2016 Paper

Nonlinear statistical reconstruction for flat-panel cone-beam CT with blur and correlated noise models

Steven Tilley, Jeffrey Siewerdsen, Wojciech Zbijewski, J. Webster Stayman

Proceedings Volume 9783, 97830R (2016) https://doi.org/10.1117/12.2216126

KEYWORDS: Systems modeling, Spatial resolution, Model-based design, Performance modeling, Computed tomography, Scanners, Algorithm development, Statistical modeling, Deconvolution, Mammography, Sensors, Data modeling, Imaging systems

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Proceedings Article | 19 March 2014 Paper

Generalized least-squares CT reconstruction with detector blur and correlated noise models

J. Webster Stayman, Wojciech Zbijewski, Steven Tilley, Jeffrey Siewerdsen

Proceedings Volume 9033, 903335 (2014) https://doi.org/10.1117/12.2043067

KEYWORDS: Spatial resolution, Sensors, Data modeling, Systems modeling, Reconstruction algorithms, Statistical modeling, Model-based design, CT reconstruction, Photons, Imaging systems

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Showing 5 of 10 publications

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