Prog Med Phys.  2025 Mar;36(1):1-7. 10.14316/pmp.2025.36.1.1.

A Novel Approach for Estimating the Effective Atomic Number Using Dual Energy

• Kim JH
• Ahn SH
• Park KW
• Kim JS

• KMID: 2566603
• DOI: http://doi.org/10.14316/pmp.2025.36.1.1

Abstract

Purpose
This study aimed to present a novel method for estimating the effective atomic number (Z_eff ) using dual-energy computed tomography (DECT) designed to improve accuracy and streamline clinical workflows by reducing computational complexity.
Methods
The proposed model leverages the DECT-derived mass attenuation coefficients without detailed compositional analysis. By incorporating additional parameters into the conventional Rutherford model, such as exponential and trigonometric functions, the model effectively captures complex variations in attenuation, enabling precise Z_eff estimation. Model fitting was performed using dual-energy data and evaluated using the percentage difference in error rates.
Results
Compared with the Rutherford model, which recorded a maximum error rate of 0.55%, the proposed model demonstrated a significantly lower maximum error rate of 0.15%, highlighting its precision. Z_eff estimates for various materials closely matched the reference values, confirming the improved accuracy of the model.
Conclusions
The proposed DECT-based model provides a practical and efficient approach to Z_eff estimation, with potential applications in radiation oncology, particularly for accurate stopping power ratio calculations in proton and heavy ion therapies.

Keyword

Effective atomic number; Dual-energy computed tomography; Stopping power ratio; Radiation oncology; Proton therapy

Figure

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  Fig. 1 Fitting result of the Rutherford model. (a) Percentage difference between NIST data and model fitting at 50 keV and 100 keV as a function of atomic number (Z); (b) Mass attenuation coefficient per Z/A (μ) as a function of atomic number (Z) at 50 keV and 100 keV, with NIST data and fitting results.

• 

  Fig. 2 Fitting result of the proposed model. (a) Percentage difference between NIST data and model fitting at 50 keV and 100 keV as a function of atomic number (Z); (b) Mass attenuation coefficient per Z/A (μ) as a function of atomic number (Z) at 50 keV and 100 keV, with NIST data and fitting results.

Reference

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