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Opportunity at National Institute of Standards and Technology (NIST)

X-Ray Computed Tomography

Location

Physical Measurement Laboratory, Sensor Science Division

RO# Location
50.68.51.C0069 Gaithersburg, MD

Please note: This Agency only participates in the February and August reviews.

Advisers

Name E-mail Phone
Garboczi, Edward Joseph edward.garboczi@nist.gov 303.497.7032
Levine, Zachary H. zlevine@nist.gov 301.975.5453

Description

As practiced, X-ray computed tomography is based on a number of assumptions. Many of these assumptions were necessary in the past due to relatively modest computational resources and may be dominated by the first application to medicine.

As systems press toward higher pixel counts and higher spatial resolution, certain effects in acquiring images that were previously neglected are becoming more important. The list of effects includes Fresnel diffraction or phase coherence effects at the boundaries of materials, which can occur even with tube sources; effects of material composition in addition to electron number density; coherent and incoherent scattering; and texture effects that make a scalar description of a voxel inadequate. In addition, the question of how to assign uncertainty to reconstructions is still an open one. Knowing this uncertainty is a key to understanding the internal structure of material images. For example, in a material containing pores and particles, one must determine whether pores are open or closed or particles are connected or disparate, and what is the actual size and shape of particles and pores when segmented from the matrix. All of these questions depend on the uncertainty of the gray scales assigned in the reconstruction algorithm, which are in turn affected by the physics questions mentioned above.

The goal is to include well-known physics in a computationally efficient way, and to follow this information through the reconstruction so as to quantitatively assign uncertainty in the final images. Ideally, between superior algorithms and superior implementation, it will be possible to build more physics into the reconstructions and thereby gain widespread acceptance in applications.

 

Keywords:
X-ray tomography; X-ray microtomography; High-speed computing; Uncertainty of reconstructions; Fresnel diffraction in tomography; Material composition in tomography;

Eligibility

Citizenship:  Open to U.S. citizens
Level:  Open to Postdoctoral applicants
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