The effect of tube voltage and current on the CT number and relative electron density in computed tomography simulator

Abstract

Background: Nowadays, the dominant role in cancer treatment is radiotherapy. For accurate dose calculations, it is necessary to provide a correct relationship between the CT numbers and electron density because the change in electron voltage and current leads to changing relationship between CT number and the relative electron density in the computed tomography simulator. Objective: To study the effect of tube voltage and current on the CT number and relative electron density in the computed tomography simulator. Methods: Two trials were performed by providing tube voltage 70, 80, 100, 120, and 140 kVp with a constant current set to 300 mAs and the second experiment was set to the constant tube voltage by adjusting the current value from the lowest to the largest. For 70 kVp vary the current from 100-500 mAs, for 80 kVp vary the current from 100-600 mAs, for 100 kVp vary the current from 100-700 mAs, for 120 kVp vary the current from 100-700 mAs and 140 kVp vary the current from 100-600 mAs. Results: The tube voltage increases the differences between RED–CT number curves due to the current variations decrease. In the range of tube voltage 100-140 kVp, the difference between CT number is 0.25 ± 1.05, 0.47 ± 3.02 and 0.02 ± 0.21, respectively. Conclusions: The appropriate tube voltage was in the range of 100-140 kVp, where the current has little effect on the relationship between the CT number and the relative electron density.