On the equivalence of image-based dual-energy CT methods for the determination of electron density and effective atomic number in radiotherapy

Christian Möhler; Patrick Wohlfahrt; Christian Richter; Steffen Greilich

doi:10.1016/j.phro.2018.03.003

On the equivalence of image-based dual-energy CT methods for the determination of electron density and effective atomic number in radiotherapy

Phys Imaging Radiat Oncol. 2018 Apr 11:5:108-110. doi: 10.1016/j.phro.2018.03.003. eCollection 2018 Jan.

Authors

Christian Möhler^{1

2}, Patrick Wohlfahrt^{3

4}, Christian Richter^{3

4

5

6}, Steffen Greilich^{1

2}

Affiliations

¹ German Cancer Research Center (DKFZ), 69120 Heidelberg, Germany.
² National Center for Radiation Research in Oncology (NCRO), Heidelberg Institute for Radiation Oncology (HIRO), 69120 Heidelberg, Germany.
³ OncoRay - National Center for Radiation Research in Oncology, Faculty of Medicine and University Hospital Carl Gustav Carus, Technische Universität Dresden, Helmholtz-Zentrum Dresden - Rossendorf, 01307 Dresden, Germany.
⁴ Helmholtz-Zentrum Dresden - Rossendorf, Institute of Radiooncology - OncoRay, 01307 Dresden, Germany.
⁵ Department of Radiation Oncology, Faculty of Medicine and University Hospital Carl Gustav Carus, Technische Universität Dresden, 01307 Dresden, Germany.
⁶ German Cancer Consortium (DKTK), 01307 Dresden, Germany.

Abstract

Dual-energy computed tomography enables the determination of relative electron density and effective atomic number. As this can increase accuracy in radiotherapy treatment planning, a substantial number of algorithms for the determination of the two quantities has been suggested - most of them based on reconstructed CT images. We show that many of these methods share a common theoretical framework. Equations can be transformed from one method to the other by re-definition of the calibration parameters. We suggest that further work should be spent on practical calibration and the reliability of CT numbers rather than on the theoretical framework.

Keywords: Dose calculation; Material characterization; Proton and ion beam therapy; Radiotherapy; Treatment planning.