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. 2022 Nov 27;22(23):9220.
doi: 10.3390/s22239220.

Improving the Accuracy of the Effective Atomic Number (EAN) and Relative Electron Density (RED) with Stoichiometric Calibration on PCD-CT Images

Kihong Son  1 , Daehong Kim  2 , Sooyeul Lee  1
Affiliations

Improving the Accuracy of the Effective Atomic Number (EAN) and Relative Electron Density (RED) with Stoichiometric Calibration on PCD-CT Images

Kihong Son et al. Sensors (Basel). .

Abstract

The photon counting detector (PCD) in computed tomography (CT) can count the number of incoming photons in order to obtain energy information for photons corresponding to user-defined thresholds. Research on the extraction of effective atomic number (EAN) and relative electron density (RED) using dual-energy CT (DECT) is currently underway. This study proposes a method for improving EAN and RED accuracy of tissue-equivalent materials by using PCD-CT-based stoichiometric calibration. After obtaining DECT images in energy bin (EB) and full spectrum (FS) modes for eight tissue-equivalent materials, the EAN was calculated with stoichiometric calibration. Using the EAN image, the RED image was acquired to evaluate the accuracy. The errors of both EAN and RED obtained with EB were within 4%. In particular, the accuracy of RED was higher than that of the FS method. Study results indicate that PCD-CT contributes to improving EAN and RED accuracy. Further studies will be aimed at reducing ring artifacts by pixel-correcting PCD images and improving stopping power ratio (SPR) measurements for dose calculation in particle therapy.

Keywords: EAN; PCD-CT; RED; dual-energy; stoichiometric calibration.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
A phantom containing eight tissue-equivalent materials. The numbers are the same as the substances in Table 1.
Figure 2
Figure 2
A photon counting detector (PCD) computed tomography (CT) system used in this study. There is a rotating platform between the X-ray source and the line type detector. Abbreviations: source to object distance (SOD); object to detector distance (ODD).
Figure 3
Figure 3
Dual-energy CT images shown with linear attenuation coefficients acquired in energy bin (EB) and full spectrum (FS) modes.
Figure 4
Figure 4
Stoichiometric curve fitting results as a function of effective atomic number (EAN) and the linear attenuation ratio for (a) energy bin (EB) and (b) full spectrum (FS) mode.
Figure 5
Figure 5
The upper row indicates effective atomic number (EAN) and relative electron density (RED) images acquired in energy bin (EB) mode. Bottom row is EAN and RED images acquired in full spectrum (FS) mode.
Figure 6
Figure 6
(a) Measured effective atomic number (EAN) and (b) relative electron density (RED) for energy bin (EB) and full spectrum (FS) modes. Mean errors of EAN for EB and FS are 2.48% and 2.04%, respectively. Mean errors of RED for EB and FS are 1.68% and 4.58%, respectively.
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