Full Content is available to subscribers

Subscribe/Learn More  >
Proceedings Article

Modeling and control of nonstationary noise characteristics in filtered-backprojection and penalized likelihood image reconstruction

[+] Author Affiliations
G. J. Gang, J. W. Stayman, W. Zbijewski, J. H. Siewerdsen

Johns Hopkins Univ. (United States)

Proc. SPIE 8668, Medical Imaging 2013: Physics of Medical Imaging, 86681G (March 19, 2013); doi:10.1117/12.2008408
Text Size: A A A
From Conference Volume 8668

  • Medical Imaging 2013: Physics of Medical Imaging
  • Robert M. Nishikawa; Bruce R. Whiting
  • Lake Buena Vista (Orlando Area), Florida, USA | February 09, 2013

abstract

Purpose: Nonstationarity of CT noise presents a major challenge to the assessment of image quality. This work presents models for imaging performance in both filtered backprojection (FBP) and penalized likelihood (PL) reconstruction that describe not only the dependence on the imaging chain but also the dependence on the object as well as the nonstationary characteristics of the signal and noise. The work furthermore demonstrates the ability to impart control over the imaging process by adjusting reconstruction parameters to exploit nonstationarity in a manner advantageous to a particular imaging task. Methods: A cascaded systems analysis model was used to model the local noise-power spectrum (NPS) and modulation transfer function (MTF) for FBP reconstruction, with locality achieved by separate calculation of fluence and system gain for each view as a function of detector location. The covariance and impulse response function for PL reconstruction (quadratic penalty) were computed using the implicit function theorem and Taylor expansion. Detectability index was calculated under the assumption of local stationarity to show the variation in task-dependent image quality throughout the image for simple and complex, heterogeneous objects. Control of noise magnitude and correlation was achieved by applying a spatially varying roughness penalty in PL reconstruction in a manner that improved overall detectability. Results: The models provide a foundation for task-based imaging performance assessment in FBP and PL image reconstruction. For both FBP and PL, noise is anisotropic and varies in a manner dependent on the path length of each view traversing the object. The anisotropy in turn affects task performance, where detectability is enhanced or diminished depending on the frequency content of the task relative to that of the NPS. Spatial variation of the roughness penalty can be exploited to control noise magnitude and correlation (and hence detectability). Conclusions: Nonstationarity of image noise is a significant effect that can be modeled in both FBP and PL image reconstruction. Prevalent spatial-frequency-dependent metrics of spatial resolution and noise can be analyzed under assumptions of local stationarity, providing a means to analyze imaging performance as a function of location throughout the image. Knowledgeable selection of a spatially-varying roughness penalty in PL can potentially improve local noise and spatial resolution in a manner tuned to a particular imaging task. Keywords: cascaded systems analysis, nonstationarity, filtered backprojection, penalized-likelihood reconstruction, noise-power spectrum, covariance matrix, imaging task, detectability index © (2013) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Citation

G. J. Gang ; J. W. Stayman ; W. Zbijewski and J. H. Siewerdsen
" Modeling and control of nonstationary noise characteristics in filtered-backprojection and penalized likelihood image reconstruction ", Proc. SPIE 8668, Medical Imaging 2013: Physics of Medical Imaging, 86681G (March 19, 2013); doi:10.1117/12.2008408; http://dx.doi.org/10.1117/12.2008408


Access This Proceeding
Sign in or Create a personal account to Buy this proceeding ($15 for members, $18 for non-members).

Figures

Tables

NOTE:
Citing articles are presented as examples only. In non-demo SCM6 implementation, integration with CrossRef’s "Cited By" API will populate this tab (http://www.crossref.org/citedby.html).

Some tools below are only available to our subscribers or users with an online account.

Related Content

Customize your page view by dragging & repositioning the boxes below.

Related Book Chapters

Topic Collections

Advertisement
  • Don't have an account?
  • Subscribe to the SPIE Digital Library
  • Create a FREE account to sign up for Digital Library content alerts and gain access to institutional subscriptions remotely.
Access This Proceeding
Sign in or Create a personal account to Buy this proceeding ($15 for members, $18 for non-members).
Access This Proceeding
Sign in or Create a personal account to Buy this article ($15 for members, $18 for non-members).
Access This Chapter

Access to SPIE eBooks is limited to subscribing institutions and is not available as part of a personal subscription. Print or electronic versions of individual SPIE books may be purchased via SPIE.org.