Room: Exhibit Hall | Forum 1
Purpose: Development and validation of a fast, Fluka-based Monte Carlo source model for patient dose calculations in a wide-beam CT scanner.
Methods: A framework to simulate a wide-beam (up to 160 mm) CT scanner using Fluka Monte Carlo particle transport code was developed. The GE Revolution scanner, with the large body filter at 120 kV, was characterized. The model was validated on AAPM TG 195 benchmark CT test problems, and on dose measurements in CTDI and anthropomorphic phantoms. Axial and helical operation modes, with Tube Current Modulation (TCM), were implemented. Particle simulations in Fluka were executed on a high-performance computing cluster.
Results: The simulation results agreed to better than an average of 4% of the reference simulation results from Report 195 test scenarios, namely: better than 2% for both test problems in case 4 using the PMMA phantom, and better than 5% of the reference result for 14 of 17 organs in case 5, and within 10% for the 3 remaining organs. The Fluka simulation results agreed to better than 2% of the air kerma measured in-air at isocenter of the scanner. The simulated air kerma in the center of the CTDI phantom overestimated the measurement by 7.5%; a correction factor was introduced to account for this. The simulated mean absorbed doses for a chest scan of the pediatric anthropomorphic phantom was completed in ~9 minutes and agreed to within the 95% CI for bone, soft tissue and lung measurements made using MOSFET detectors for fixed current axial and helical scans as well as helical scan with TCM.
Conclusion: A fast, Fluka-based Monte Carlo simulation model of axial and helical acquisition techniques using a wide-beam CT scanner demonstrated good agreement between measured and simulated results for both fixed current and TCM in complex geometry.