Purpose: This work creates a novel tool that significantly improves our understanding of distribution of scattered radiation in modern clinical diagnostic CT.
Methods: A hybrid simulation method was developed to estimate the distribution of scatter radiation in a Philips Brilliance Big-bore CT scanner. Radiation transport was simulated with Geant4 in the scanned object and all components of the CT, up to entry of scatter into the 1D antiscatter grid (ASG). Wherein the ASG, an analytical method was employed to quantify the scatter transmission factor. Highly accurate geometry of CT components, including bowtie filter was modeled based on CAD meshing technique and incorporated in Geant4 simulation. The standard electromagnetic physics, emstandard_opt4, which has the most up-to-date cross-section for low-energy photon was used in the simulation. The scatter-to-primary ratio (SPR) of the CT system were acquired for 90 kVp and 140 kVp.
Results: SPR under variety of imaging condition, such as imaging with bowtie, with ASG, with different collimations (i.e., 3 mm, 6mm, 12 mm, and 24 mm) were obtained quantitatively. We observed that SPR lineally increase with collimation size. SPR of 90 kVp is lightly higher than 140 kVp, e.g., up to 0.14% with 24 mm collimation. Bowtie filter slightly reduces SPR, e.g., up to 0.5% for 90 kVp with 24 mm collimation, and up to 0.2% for 140 kVp with 24 mm collimation. ASG can substantially reduces SPR, e.g., up to 5.5% for 90 kVp with 24 mm collimation, and up to 3.8% for 140 kVp with 24mm collimation.
Conclusion: In this study, we developed a hybrid simulation method to systematically quantify the scatter radiation distribution for the Big-bore CT. According to the simulation results, we found that the bowtie filter can slightly reduce the scatter radiation, and the ASG can substantially reduce the scatter radiation.
Funding Support, Disclosures, and Conflict of Interest: This study was supported by NIH RO1 CA 212638.
Not Applicable / None Entered.