The large contribution of scatter to cone-beam computed tomography (CBCT) x-ray projections significantly degrades
image quality, both through streaking and cupping artifacts and by loss of low contrast boundary detectability. The goal
of this investigation is to compare the efficacy of three widely used scatter mitigation methods: subtractive scatter
correction (SSC); anti-scatter grids (ASG); and beam modulating with bowtie filters; for improving signal-to-noise ratio
(SNR), contrast, contrast-to-noise ratio (CNR) and cupping artifacts. A simple analytic model was developed to predict
scatter-to-primary ratio (SPR) and CNR as a function of cylindrical phantom thickness. In addition, CBCT x-ray
projections of a CatPhan QA phantom were measured, using a Varian CBCT imaging system, and computed, using an
inhouse Monte Carlo photon-transport code to more realistically evaluate the impact of scatter mitigation techniques.
Images formed with uncorrected sinograms acquired without ASGs and bow-tie filter show pronounced cupping
artifacts and loss of contrast. Subtraction of measured scatter profiles restores image uniformity and CT number
accuracy, but does not improve CNR, since the improvement in contrast almost exactly offset by the increase in relative
x-ray noise. ASGs were found to modestly improve CNR (up to 20%, depending ASG primary transmission and
selectivity) only in body scans, while they can reduce CNR for head phantoms where SPR is low.