TY - GEN
T1 - Evaluation of scatter mitigation strategies for X-ray cone-beam CT
T2 - Medical Imaging 2007: Physics of Medical Imaging
AU - Lazos, Dimitrios
AU - Lasio, Giovanni
AU - Evans, Joshua
AU - Williamson, Jeffrey F.
PY - 2007
Y1 - 2007
N2 - 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.
AB - 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.
KW - Artifacts
KW - Cone-beam computed tomography
KW - Reconstruction
KW - Simulation
UR - http://www.scopus.com/inward/record.url?scp=35148827537&partnerID=8YFLogxK
U2 - 10.1117/12.713610
DO - 10.1117/12.713610
M3 - Conference contribution
AN - SCOPUS:35148827537
SN - 081946628X
SN - 9780819466280
T3 - Progress in Biomedical Optics and Imaging - Proceedings of SPIE
BT - Medical Imaging 2007
Y2 - 18 February 2007 through 22 February 2007
ER -