Correlation between CT attenuation value and iodine concentration in vitro: Discrepancy between gemstone spectral imaging on single-source dual-energy CT and traditional polychromatic X-ray imaging

Objectives: To estimate the minimum detectable iodine concentration on multiple dual-energy CT (DECT) platforms. Methods and materials: A phantom containing iodine concentrations ranging from 0 to 10 mg ml−1 was scanned with five dual-energy platforms (two rapid kilo volt switching (r-kVs), one dual source (DS), one sequential acquisition and one split-filter). Serial dilutions of 300 mg ml−1 iodinated contrast material were used to generate concentrations below 2 mg ml−1. Iodine density and virtual monoenergetic images were reviewed by three radiologists to determine the minimum visually detectable iodine concentration. Contrast-to-noise ratios (CNRs) were calculated. Results: 1 mg mL−1 (~0.8 mg mL−1 corrected) was the minimum visually detectable concentration among the platforms and could be seen by all readers on the third-generation r-kVs and DS platforms. Conclusions: At low concentrations, CNR for monoenergetic images was highest on the DS platform and lowest in the sequential acquisition and split-filter platforms. Advances in knowledge: The results of this study corroborate previous in vivo estimates of iodine detection limits at DECT and provide a comparison for the performance of different DECT platforms at low iodine concentrations in vitro.

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Dual-energy x-ray imaging technique for in vitro tissue composition measurement

Medical Physics ◽

10.1118/1.597283 ◽

1994 ◽

Vol 21 (11) ◽

pp. 1807-1815 ◽

Cited By ~ 10

Author(s):

M. Moreau ◽

D. W. Holdsworth ◽

A. Fenster

Keyword(s):

Imaging Technique ◽

Dual Energy ◽

Tissue Composition ◽

X Ray ◽

X Ray Imaging ◽

Composition Measurement

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A Spectrum-Adaptive Decomposition Method for Effective Atomic Number Estimation Using Dual Energy CT

Electronic Imaging ◽

10.2352/issn.2470-1173.2020.14.coimg-293 ◽

2020 ◽

Vol 2020 (14) ◽

pp. 293-1-293-7

Author(s):

Ankit Manerikar ◽

Fangda Li ◽

Avinash C. Kak

Keyword(s):

Atomic Number ◽

Decomposition Method ◽

Traditional Approach ◽

Effective Atomic Number ◽

Dual Energy ◽

Performance Comparison ◽

Estimation Methods ◽

Dual Energy Ct ◽

Projection Data ◽

X Ray

Dual Energy Computed Tomography (DECT) is expected to become a significant tool for voxel-based detection of hazardous materials in airport baggage screening. The traditional approach to DECT imaging involves collecting the projection data using two different X-ray spectra and then decomposing the data thus collected into line integrals of two independent characterizations of the material properties. Typically, one of these characterizations involves the effective atomic number (Zeff) of the materials. However, with the X-ray spectral energies typically used for DECT imaging, the current best-practice approaches for dualenergy decomposition yield Zeff values whose accuracy range is limited to only a subset of the periodic-table elements, more specifically to (Z < 30). Although this estimation can be improved by using a system-independent ρe — Ze (SIRZ) space, the SIRZ transformation does not efficiently model the polychromatic nature of the X-ray spectra typically used in physical CT scanners. In this paper, we present a new decomposition method, AdaSIRZ, that corrects this shortcoming by adapting the SIRZ decomposition to the entire spectrum of an X-ray source. The method reformulates the X-ray attenuation equations as direct functions of (ρe, Ze) and solves for the coefficients using bounded nonlinear least-squares optimization. Performance comparison of AdaSIRZ with other Zeff estimation methods on different sets of real DECT images shows that AdaSIRZ provides a higher output accuracy for Zeff image reconstructions for a wider range of object materials.

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