Upgrading a Computed Tomography Dose Index (CTDI) Phantom to an Electron Density (ED) Phantom for Commissioning a CT Simulator

Abstract

Introduction: A crucial step in commissioning a CT simulator is measuring the conversion relationship between the CT number and Relative Electron Density (RED) and transferring it to the radiotherapy TPS for accurate dose calculation. Material and Methods: In order to automatically reconstruct a DE-Rho series with relative electron density maps of the materials used, 14 tissue-mimicking material plugs were made, their properties were measured, and the developed density phantom was scanned by CT-simulator using the Dual Energy^DE_Direct Density protocol. Results: CT numbers (HU) for various densities of materials were determined. Utilizing the resultant HU from CT scans, the relative electron density, or RED, was computed. The HU-RED calibration curve was created using CT scans that were obtained with different tissue replacements. Conclusion: Particularly for the CT-number calibration in radiation therapy planning, the new Tissue Equivalent Materials (TEMs) may simplify the calibration process without sacrificing the accuracy of the stoichiometric calibration. Our objective was met and the purchase cost was avoided thanks to the developed phantom.

Keywords

• radiotherapy
• treatment planning system
• computed tomography
• calibration curve
• density phantom
• relative electron density