Evaluation of scatter mitigation strategies for X-ray cone-beam CT: Impact of scatter subtraction and anti-scatter grids on contrast-to-noise ratio

Dimitrios Lazos, Giovanni Lasio, Joshua Evans, Jeffrey F. Williamson

Research output: Chapter in Book/Report/Conference proceedingConference contribution

2 Scopus citations

Abstract

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.

Original languageEnglish
Title of host publicationMedical Imaging 2007
Subtitle of host publicationPhysics of Medical Imaging
EditionPART 1
DOIs
StatePublished - Oct 15 2007
Externally publishedYes
EventMedical Imaging 2007: Physics of Medical Imaging - San Diego, CA, United States
Duration: Feb 18 2007Feb 22 2007

Publication series

NameProgress in Biomedical Optics and Imaging - Proceedings of SPIE
NumberPART 1
Volume6510
ISSN (Print)1605-7422

Conference

ConferenceMedical Imaging 2007: Physics of Medical Imaging
CountryUnited States
CitySan Diego, CA
Period02/18/0702/22/07

Keywords

  • Artifacts
  • Cone-beam computed tomography
  • Reconstruction
  • Simulation

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    Lazos, D., Lasio, G., Evans, J., & Williamson, J. F. (2007). Evaluation of scatter mitigation strategies for X-ray cone-beam CT: Impact of scatter subtraction and anti-scatter grids on contrast-to-noise ratio. In Medical Imaging 2007: Physics of Medical Imaging (PART 1 ed.). [65101V] (Progress in Biomedical Optics and Imaging - Proceedings of SPIE; Vol. 6510, No. PART 1). https://doi.org/10.1117/12.713610