Room: Track 1
Purpose: To determine the spectral separation and dose allocation of the low- and high-energy components of the Siemens TwinBeam split-filter (SF) dual-energy CT (DECT) system and to investigate the potential benefits of increased tube voltage using a benchmarked equivalent source model.
Methods and Materials: Measurements of half-value-layer (HVL) and fan beam profile were used to adjust the equivalent inherent filtration thickness and bowtie filter dimensions to benchmark an equivalent source model of the Siemens SOMATOM Definition Edge 120 kVp beam in MCNP6. A model of the SF was created based on manufacturer specifications and placed within the MCNP6 source model. Simulations were performed to determine the mean energy and spectral separation of the low- and high-energy portions of the 120 kVp split beam. Dose allocation was defined as the ratio of dose from the low-energy components to the total dose at the center of a cylindrical water phantom of radii ranging from 10-20 cm. This methodology was repeated with an increased tube voltage of 140 kVp.
Results: The mean energies of the low- and high-energy components of the TwinBeam equivalent source model were 66.2±0.10 keV and 82.7±0.18 keV, respectively. The spectral separation, defined as the difference in mean energy, was 16.5±0.8 keV. The mean energies and spectral separation increased to 71.9±0.072 keV, 92.9±0.15 keV, and 21.1±0.4 keV, respectively for the 140 kVp+SF source model. The dose contribution from the low-energy portion of the beam was largest for the 10 cm radius phantom at 63% and 65% for the 120 kVp+SF and 140 kVp+SF models, respectively and became indistinguishable with increased radii.
Conclusions: Two equivalent source models of single-source SF DECT with a 120 kVp and 140 kVp were created. There was a greater spectral separation and dose allocation when the tube voltage increased from 120 kVp to 140 kVp.