Engineering topics
Smith, Jerel A.
Publications and source records attributed to Smith, Jerel A..
Livermore tomography tools: Accurate, fast, and flexible software for tomographic science
Livermore Tomography Tools (LTT) is a customizable scientific software package that enables a broad range of research and development efforts into computed tomography (CT). Here, it was developed to process x-ray and neutron CT data accurately and rapidly from raw detector counts to reconstructed volumes with the flexibility to handle many special cases. LTT fulfills long-term CT software goals to provide quantitatively accurate results reported in physical units (e.g., mm -1 or cm -1 ) while exploiting all available computational advantages to maximize speed. Written in C/C++ with support for multiple CPUs and GPUs, LTT runs on many computing platforms (Linux/Unix, Windows, and Mac; laptops to supercomputers). As a result, LTT can:process data acquired from various custom-built and commercially available CT scanners, model and simulate x-ray and neutron interactions to encourage algorithm prototyping, and allow for rapid insertion of the latest algorithms.We describe LTT’s software architecture, user interfaces, and its 88 algorithms (as of this writing) for pre-processing, reconstruction, post-processing, and simulation that support many scanner geometries (parallel-, fan-, cone-beam, and custom). Several applications are presented that illustrate LTT’s accuracy, speed, and flexibility relative to other solutions.
System-independent characterization of materials using dual-energy computed tomography
A system for characterizing the material of an object scanned via a dual-energy computed tomography scanner is provided. The system generates photoelectric and Compton sinograms based on a photoelectric-Compton decomposition of low-energy and high-energy sinograms generated from the scan and based on a scanner spectral response model. The system generates a Compton volume with Compton attenuation coefficients from the Compton sinogram and a photoelectric volume with photoelectric attenuation coefficients from the photoelectric sinogram. The system generates an estimated effective atomic number for a voxel and an estimated electron density for the voxel from the Compton attenuation coefficient and photoelectric coefficient for the voxel and scanner-specific parameters. The system then characterizes the material within the voxel based on the estimated effective atomic number and estimated electron density for the voxel. This information can be used to provide a mapping of known effective atomic numbers and known electron densities to known materials.
Method to Extract System-Independent Material Properties From Dual-Energy X-Ray CT
In 2016, we published a method for processing dual-energy computed tomography (DECT) data called system-independent rho-e/Z-e (ρ e /Z e ) or SIRZ. Using data from multiple DECT systems and spectra, SIRZ estimated the electron density ρ e and effective atomic number Z e (based on published X-ray cross sections), for a set of known specimens. However, the decomposition process required complex spectral modeling of the DECT system, which made SIRZ difficult to implement and automate. This paper describes the subsequent work on “SIRZ-2” to simplify the spectral modeling, automate the process, and improve its range and versatility. The SIRZ-2 basis functions are more accurate for the X-ray energy range (<;200 keV) and materials that are common to DECT applications in security and nondestructive characterization. To evaluate the SIRZ-2 performance, eight well-characterized specimens (with Z e of 6-20) were scanned with multiple spectral pairs (up to 200 keV) on seven different DECT systems, including a commercial airport luggage scanner. For these varied tests, the average SIRZ-2 relative errors for ρ e estimates were four times lower (0.7% compared to 3.0% for SIRZ), while average Z e relative errors were comparably low for both methods (<;1.5%). Average precision errors were also low (<;2.3% for both). SIRZ-2 produces accurate, repeatable, and system-independent material property estimates of (ρ e , Z e ) that can be directly compared across DECT systems and over time.
System-independent characterization of materials using dual-energy computed tomography
In this study, we present a new decomposition approach for dual-energy computed tomography (DECT) called SIRZ that provides precise and accurate material description, independent of the scanner, over diagnostic energy ranges (30 to 200 keV). System independence is achieved by explicitly including a scanner-specific spectral description in the decomposition method, and a new X-ray-relevant feature space. The feature space consists of electron density, ρ e , and a new effective atomic number, Z e , which is based on published X-ray cross sections. Reference materials are used in conjunction with the system spectral response so that additional beam-hardening correction is not necessary. The technique is tested against other methods on DECT data of known specimens scanned by diverse spectra and systems. Uncertainties in accuracy and precision are less than 3% and 2% respectively for the (ρ e , Z e ) results compared to prior methods that are inaccurate and imprecise (over 9%).
Documentation of the ISA Micro Computed Tomography System
This document is intended to provide information on the ISA Micro Computed Tomography (MicroCT) system that will be installed in Yavne, Israel. X-ray source, detector, and motion control hardware are specified as well as specimen platforms, containers, and reference material types. Most of the details on the system are derived from Reference 1 and 2.
Plan for the Purchase of MCT and EDS Reference Materials, Source Filters, Cu Strips, and Carousel Sub-Assemblies
The goal of this effort is to improve the quality and consistency of MCT and EDS data across the program. New references, aluminum (Al) and Cu filters, and Cu strips will be of known high purity and quality, traceable to documented chemical analyses. A single Program organization will be responsible to purchase, fabricate, assemble, inspect, control, and supply these items to the Program to ensure adequate and uniform quality and quality control.
TP75-MicroCT Test Bed Data Acquisition for Multi-Energy Zeff and Rho-e Decomposition Analysis
LLNL has been tasked to develop a system independent method that will characterize Home Made Explosives (HME) materials. The objective of this test plan is to acquire Computed Tomography (CT) data on two LLNL systems (MCT-TB and HEAF). The CT data will be used in evaluating potential System Independent Decomposition methods.
ZeCalc Algorithm Details
This report documents the implementation of the Java application ZeCalc (as released in version 3 on October 18, 2012), which calculates “Z e ”, a newly-defined “effective atomic number” for mixtures and compounds. Z e differs from the traditional Z eff in that it is based upon the x-ray cross section of the material, so it is more amenable to radiographic applications. Additionally, ZeCalc calculates ρ e , the volumetric electron density (with units of electron‐mol/cm 3 ), for materials with a specified composition and volumetric mass density, ρ m with units of g/cm 3 ).
Case for an Improved Effective-Atomic Number for the Electronic Baggage Scanning Program (Rev. 1)
Z eff , a parameter representing an “effective atomic number” for a material, plays an important role in the Electronic Baggage Scanning Program (EBSP) to detect threats in dual-energy computed tomography (CT) baggage-scanning systems. We believe that Zeff, as defined and used on this program, does not provide the most accurate representation of a material's x-ray properties.. We present the case for a new method that defines an effective atomic number for compounds and mixtures, which we refer to as Z e . Unlike Z eff , Z e is tied by definition to the x-ray absorption properties of each specific material. Use of this alternative will provide a more accurate scale for calibrating LLNL-designed Micro-CT systems and vendor-built Explosives Detection Systems (EDS) against standard reference materials, and it will provide a more accurate physical characterization of the x-ray properties of materials evaluated on those systems. This document, (1) Describes the current usage of the Z eff parameter; (2) Details problems entailed in the use of the Z eff parameter; (3) Proposes a well-defined alternative—Z e ; (4) Proposes and demonstrates an algorithm for optimally associating Z e with any specified compound or mixture; (5) Discusses issues that can impact the usefulness of an effective-Z model; and (6) Recommends that, in order that the chosen effective-Z parameter not materially impact the accuracy of data produced by the EBSP program, the use of Z eff be replaced by Z e .