Construction of a computational MDCT model for simulations of the detector signals

Objective

To develop a computational model of a multi-detector CT scanner (MDCT), which could be used to simulate the signal of each detector element in the MDCT by using the Monte Carlo method.

Methods

The CT scanner was modelled, including the X-ray source, the bowtie filter, the collimator, the couch and the detector panel. Under a general scanning condition, the signal in each detector element was simulated based on the model by using the MCNPX code. Both the energy spectra at different tube voltages and energy deposition in the detector panel at different collimations were simulated to test the robustness of the MDCT model built in this study. Furthermore, the simulated signals in each detector element were compared with their recorded signals. The accuracies were evaluated by the relative root mean square error (RRMSE) and the structural similarity (SSIM) for each detector element and the whole detector panel, respectively.

Results

The simulated energy spectra before and after passing through the phantom and simulated energy deposition in the detector panel were rational. In the scan range from the apex of lung to pubic symphysis, the RRMSE of the 18 axial projections ranged from 0.02 to 0.17, with an average of 0.08. And the SSIMs were calculated to be 0.979 and 0.976 for projections with the largest peak signal and the smallest peak signal, respectively.

Conclusions

The computational model of the MDCT developed in this study is accurate and successful, it is helpful for further accurate simulations of the radiation dose and image quality of the MDCT.