Evaluation of dose calculation in Direct Density algorithm reconstruction images using dual energy CT for Radiotherapy

Abstract

Background

Computed tomography (CT) is used in the simulation and treatment planning process. The dose calculation is based on the HU-ED calibration curve, which varies with tube voltages. A single HU-ED curve of standard 120 kV is used for dose calculation. However, Direct Density algorithm can reconstruct images from different tube voltages, regardless of the HU-ED calibration curve. This study aims to evaluate the radiation doses between the standard kV and the Direct Density reconstruction images.

Methods

The image acquisition and data collection followed the machine protocol. Electron density phantom was scanned with Brain, Head and Neck, Breast, Abdomen and Pelvis protocol, the scanning was performed for all the tube voltages including 70, 80, 100, 120 and 140 kV. HU-ED curves from standard kV and Direct Density reconstruction were created in the treatment planning system. After that, the homogeneous phantom (Solid water phantom) and heterogeneous phantom were scanned using Thorax and Head and neck protocol. The radiation doses between the standard kV images (120 kV) and the Direct Density reconstruction images in different tube voltages including 80, 100, 120, and 140 kV were compared.

Results

The results showed that the dose calculation did not show the difference between the standard kV and the Direct Density reconstruction for all the tube voltage in homogeneous and heterogeneous phantom at p-value < 0.05.

Conclusion

The difference in the radiation dose was less than 1%, indicating that images obtained from Direct Density reconstruction can be used to calculate radiation doses in clinical practice. Moreover, the patient dose can be reduced by selecting lower energy levels in the simulation process.