An x-ray computed tomography (CT) simulator based on the Monte Carlo
N-particle radiation transport computer code (MCNP4C) was developed for
simulation of both fan- and cone-beam CT scanners. A user-friendly interface
running under Matlab 6.5.1 creates the scanner geometry at different views
as MCNP4C’s input file. The full simulation of x-ray tube, phantom
and detectors with single-slice, multi-slice and flat detector configurations
was considered. The simulator was validated through comparison with
experimental measurements of different nonuniform phantoms with varying
sizes on both a clinical and a small-animal CT scanner. There is good
agreement between the simulated and measured projections and reconstructed
images. Thereafter, the effects of bow-tie filter, phantom size and septa length
on scatter distribution in fan-beam CT were studied in detail. The relative
difference between detected total, primary and scatter photons for septa length
varyingbetween0and95mmis11.2%,1.9%and84.1%,respectively,whereas
the scatter-to-primary ratio decreases by 83.8%. The developed simulator is a
powerfultoolforevaluatingtheeffectofphysical, geometricalandotherdesign
parameters on scanner performance and image quality in addition to offering a
versatile tool for investigating potential artefacts and correction schemes when
using CT-based attenuation correction on dual-modality PET/CT units.
Development and validation of MCNP4C-based Monte Carlo simulator for fan- and cone-beam x-ray CT