Abstract
Purpose: Nonstationarity is an important aspect of imaging performance in CT and cone-beam CT (CBCT), especially for systems employing iterative reconstruction. This work presents a theoretical framework for both filtered-backprojection (FBP) and penalized-likelihood (PL) reconstruction that includes explicit descriptions of nonstationary noise, spatial resolution, and task-based detectability index. Potential utility of the model was demonstrated in the optimal selection of regularization parameters in PL reconstruction. Methods: Analytical models for local modulation transfer function (MTF) and noise-power spectrum (NPS) were investigated for both FBP and PL reconstruction, including explicit dependence on the object and spatial location. For FBP, a cascaded systems analysis framework was adapted to account for nonstationarity by separately calculating fluence and system gains for each ray passing through any given voxel. For PL, the point-spread function and covariance were derived using the implicit function theorem and first-order Taylor expansion according toFessler [Mean and variance of implicitly defined biased estimators (such as penalized maximum likelihood): Applications to tomography, IEEE Trans. Image Process. 5(3),
Original language | English (US) |
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Article number | 081902 |
Journal | Medical physics |
Volume | 41 |
Issue number | 8 |
DOIs | |
State | Published - 2014 |
Keywords
- cascaded systems analysis
- cone-beam CT
- detectability index
- image quality
- imaging task
- modulation transfer function
- noise-power spectrum
- nonstationary noise
- penalized-likelihood reconstruction
- statistical reconstruction
ASJC Scopus subject areas
- Biophysics
- Radiology Nuclear Medicine and imaging