Highlights
- •DLCT allows to estimate electron densities and effective atomic number.
- •DLCT system provided an accuracy to determine electron density (<0.1%).
- •An accuracy to determine atomic number was varied widely with mean −2.0%.
- •Stopping power ratio can be estimated with an accuracy of 0.3%.
- •The accurate measurements could improve dose calculation in radiotherapy treatment.
Abstract
Purpose
Assess the accuracy for quantitative measurements of electron density relative to
water (ρe/ρe,w), effective atomic number (Zeff) and stopping power ratio relative to water (SPRw) using a dual-layer computed tomography (DLCT) system.
Methods and Materials
A tissue characterization phantom was scanned using DLCT with varying scanning parameters
(i.e., tube voltage, rotation time, CTDIvol, and scanning mode) and different reference materials. Then, electron density ρe/ρe,w and atomic number Zeff images were reconstructed, and their values were determined for each reference materials.
Based on these two values, SPRw was calculated. Finally, the percent error (PE) against the theoretical values was
calculated for reference materials.
Results
Significant linear relationships (p < 0.001) were observed between the measured and theoretical ρe/ρe,w (r = 1.000), Zeff (r = 0.989) and SPRw (r = 1.000) values. The PE for each reference material varied from –2.0 to 1.2% (mean,
<0.1%) for electron density ρe/ρe,w, from –6.4 to 8.0% (mean, –2.0%) for atomic number Zeff, and from –2.0 to 1.9% (mean, 0.3%) for stopping power ratio SPRw. The mean PE of ρe/ρe,w (<0.1%), Zeff (<–2.5%) and SPRw (<0.4%) was verified across the variation of scanning parameters (p > 0.85).
Conclusions
DLCT provides a reasonable accuracy in the measurements of ρe/ρe,w, Zeff and SPRw, and could enhance radiotherapy treatment planning and the subsequent outcomes.
Abbreviations:
DECT (dual-energy CT), DLCT (dual-layer CT), SPR (stopping power ratio), PE (percent error)Keywords
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Article info
Publication history
Accepted:
November 15,
2018
Received in revised form:
September 25,
2018
Received:
May 18,
2018
Identification
Copyright
© 2018 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.
