Dr. Richard A. Ketcham Profile

Dr. Richard A. Ketcham

at Univ of Texas at Austin

SPIE Involvement:

Author

Publications (2)

This will count as one of your downloads.

You will have access to both the presentation and article (if available).

DOWNLOAD NOW

This content is available for download via your institution's subscription. To access this item, please sign in to your personal account.

Email or Username Forgot your username?

Password Forgot your password?

Show

Keep me signed in

No SPIE account? Create an account

Proceedings Article | 10 September 2019 Presentation + Paper

Resolution-invariant measurements of small objects in polychromatic CT data

Richard Ketcham

Proceedings Volume 11113, 111130B (2019) https://doi.org/10.1117/12.2532082

KEYWORDS: Particles, Gold, Point spread functions, Signal attenuation, Calibration, Image segmentation, Computed tomography, 3D metrology, X-rays

Read Abstract +

Features such as particles, pores, or cracks are challenging to measure accurately in CT data when they are small relative to the data resolution, characterized as a point-spread function (PSF). These challenges are particularly acute when paired with segmentation, as the PSF distributes some of the signal from a voxel among neighboring ones; effectively dispersing some of the signal from a given object to a region outside of it. Any feature of interest with one or more dimensions on the order of the PSF will be impacted by this effect, and measurements based on global thresholds necessarily fail. Measurements of the same features should be consistent across different instruments and data resolutions. The PVB (partial volume and blurring) method successfully compensates by quantifying features that are small in all three dimensions based on their attenuation anomaly. By calibrating the CT number of the phase of interest (in this case, gold) it is possible to accurately measure particles down to <6 voxels in data acquired on two instruments, 14 years apart, despite severe artifacts. Altogether, the PVB method is accurate, reproducible, resolution-invariant, and objective; it is also notable for its favorable error structure. The principal challenge is the need for representative effective CT numbers, which reflect not only the features of interest themselves, but also the X-ray spectrum, the size, shape and composition of the enclosing sample, and processing details such as beam-hardening correction. Empirical calibration is the most effective approach.

Proceedings Article | 7 September 2006 Paper

New algorithms for ring artifact removal

Richard Ketcham

Proceedings Volume 6318, 63180O (2006) https://doi.org/10.1117/12.680939

KEYWORDS: Sensors, Data acquisition, Image processing, X-rays, Tomography, Signal attenuation, Calibration, Brain, Reconstruction algorithms, Interfaces

Read Abstract +

This paper describes a set of algorithms that enable virtually complete ring artifact removal from tomographic imagery with minimal to negligible contamination of the underlying data. These procedures were created specifically to deal with data as acquired at the University of Texas high-resolution X-ray CT facility, but are likely to be applicable in other settings as well. In most cases corrections are optimally applied to sinogram data before reconstruction, but a variant is developed for correcting already-reconstructed images. The algorithms make particular use of repetitive aspects of the artifact across images to improve behavior. However, fully utilizing this functionality requires processing entire data sets simultaneously, rather than one image at a time. A number of parameters may be adjusted to optimize results for particular data sets.

My Library

You currently do not have any folders to save your paper to! Create a new folder below.

Folder Name

Folder Description

View contact details

UPDATE YOUR PROFILE

Is this your profile? Update it now.

Sign into your SPIE.org account

Don’t have a profile and want one?

Create an account on SPIE.org

Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks. You are receiving this notice because your organization may not have SPIE eBooks access.*

*Shibboleth/Open Athens users─please sign in to access your institution's subscriptions.

To obtain this item, you may purchase the complete book in print or electronic format on SPIE.org.

ORGANIZATIONAL
Sign in with credentials provided by your organization.

Organizational Username

Organizational Password

Show/Hide Password

INSTITUTIONAL
Select your institution to access the SPIE Digital Library.

SELECT YOUR INSTITUTION

PERSONAL
Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.

PERSONAL SIGN IN

No SPIE Account? Create one

PURCHASE THIS CONTENT

SUBSCRIBE TO DIGITAL LIBRARY

50 downloads per 1-year subscription

Members: $195

Non-members: $335 ADD TO CART

25 downloads per 1 - year subscription

Members: $145

Non-members: $250 ADD TO CART

PURCHASE SINGLE ARTICLE

Includes PDF, HTML & Video, when available

Members:

Non-members: ADD TO CART

Keywords/Phrases

Search In:

Publication Years