Noise reduction for low-dose helical CT by fully 3D penalized weighted least-squares sinogram smoothing

Jing Wang, Tianfang Li, Hongbing Lu, Zhengrong Liang

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

1 Scopus citations


Helical computed tomography (HCT) has several advantages over conventional step-and-shoot CT for imaging a relatively large object, especially for dynamic studies. However, HCT may increase X-ray exposure significantly to the patient. This work aims to reduce the radiation by lowering the X-ray tube current (mA) and filtering the low-mA (or dose) sinogram noise. Based on the noise properties of HCT sinogram, a three-dimensional (3D) penalized weighted least-squares (PWLS) objective function was constructed and an optimal sinogram was estimated by minimizing the objective function. To consider the difference of signal correlation among different direction of the HCT sinogram, an anisotropic Markov random filed (MRP) Gibbs function was designed as the penalty. The minimization of the objection function was performed by iterative Gauss-Seidel updating strategy. The effectiveness of the 3D-PWLS sinogram smoothing for low-dose HCT was demonstrated by a 3D Shepp-Logan head phantom study. Comparison studies with our previously developed KL domain PWLS sinogram smoothing algorithm indicate that the KL+2D-PWLS algorithm shows better performance on in-plane noise-resolution trade-off while the 3D-PLWS shows better performance on r-axis noise-resolution trade-off. Receiver operating characteristic (ROC) studies by using channelized Hotelling observer (CHO) shows that 3D-PWLS and KL+2DPWLS algorithms have similar performance on detectability in low-contrast environment.

Original languageEnglish (US)
Title of host publicationMedical Imaging 2006
Subtitle of host publicationPhysics of Medical Imaging
StatePublished - Jun 30 2006
EventMedical Imaging 2006: Physics of Medical Imaging - San Diego, CA, United States
Duration: Feb 12 2006Feb 16 2006

Publication series

NameProgress in Biomedical Optics and Imaging - Proceedings of SPIE
Volume6142 III
ISSN (Print)1605-7422


OtherMedical Imaging 2006: Physics of Medical Imaging
Country/TerritoryUnited States
CitySan Diego, CA


  • 3D PWLS criterion
  • Anisotropic MRP Gibbs function
  • Low-dose HCT
  • Noise reduction
  • ROC curves of CHO observer studies
  • Sinogram smoothing

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Biomaterials
  • Atomic and Molecular Physics, and Optics
  • Radiology Nuclear Medicine and imaging


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