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BibTeX
Iterative image-domain decomposition for dual-energy CT
Medical physics (Lancaster), 2014-04, Vol.41 (4), p.041901-n/a
Niu, Tianye
Dong, Xue
Petrongolo, Michael
Zhu, Lei
2014
Details
Autor(en) / Beteiligte
Niu, Tianye
Dong, Xue
Petrongolo, Michael
Zhu, Lei
Titel
Iterative image-domain decomposition for dual-energy CT
Ist Teil von
Medical physics (Lancaster), 2014-04, Vol.41 (4), p.041901-n/a
Ort / Verlag
United States: American Association of Physicists in Medicine
Erscheinungsjahr
2014
Link zum Volltext
Quelle
Wiley Online Library All Journals
Beschreibungen/Notizen
Purpose: Dual energy CT (DECT) imaging plays an important role in advanced imaging applications due to its capability of material decomposition. Direct decomposition via matrix inversion suffers from significant degradation of image signal-to-noise ratios, which reduces clinical values of DECT. Existing denoising algorithms achieve suboptimal performance since they suppress image noise either before or after the decomposition and do not fully explore the noise statistical properties of the decomposition process. In this work, the authors propose an iterative image-domain decomposition method for noise suppression in DECT, using the full variance-covariance matrix of the decomposed images. Methods: The proposed algorithm is formulated in the form of least-square estimation with smoothness regularization. Based on the design principles of a best linear unbiased estimator, the authors include the inverse of the estimated variance-covariance matrix of the decomposed images as the penalty weight in the least-square term. The regularization term enforces the image smoothness by calculating the square sum of neighboring pixel value differences. To retain the boundary sharpness of the decomposed images, the authors detect the edges in the CT images before decomposition. These edge pixels have small weights in the calculation of the regularization term. Distinct from the existing denoising algorithms applied on the images before or after decomposition, the method has an iterative process for noise suppression, with decomposition performed in each iteration. The authors implement the proposed algorithm using a standard conjugate gradient algorithm. The method performance is evaluated using an evaluation phantom (Catphan©600) and an anthropomorphic head phantom. The results are compared with those generated using direct matrix inversion with no noise suppression, a denoising method applied on the decomposed images, and an existing algorithm with similar formulation as the proposed method but with an edge-preserving regularization term. Results: On the Catphan phantom, the method maintains the same spatial resolution on the decomposed images as that of the CT images before decomposition (8 pairs/cm) while significantly reducing their noise standard deviation. Compared to that obtained by the direct matrix inversion, the noise standard deviation in the images decomposed by the proposed algorithm is reduced by over 98%. Without considering the noise correlation properties in the formulation, the denoising scheme degrades the spatial resolution to 6 pairs/cm for the same level of noise suppression. Compared to the edge-preserving algorithm, the method achieves better low-contrast detectability. A quantitative study is performed on the contrast-rod slice of Catphan phantom. The proposed method achieves lower electron density measurement error as compared to that by the direct matrix inversion, and significantly reduces the error variation by over 97%. On the head phantom, the method reduces the noise standard deviation of decomposed images by over 97% without blurring the sinus structures. Conclusions: The authors propose an iterative image-domain decomposition method for DECT. The method combines noise suppression and material decomposition into an iterative process and achieves both goals simultaneously. By exploring the full variance-covariance properties of the decomposed images and utilizing the edge predetection, the proposed algorithm shows superior performance on noise suppression with high image spatial resolution and low-contrast detectability.
Sprache
Englisch
Identifikatoren
ISSN: 0094-2405
eISSN: 2473-4209
DOI: 10.1118/1.4866386
Titel-ID: cdi_crossref_primary_10_1118_1_4866386
Format
–
Schlagworte
ALGORITHMS
,
best linear unbiased estimation
,
Biological material, e.g. blood, urine
,
Haemocytometers
,
Computed tomography
,
Computerised tomographs
,
computerised tomography
,
COMPUTERIZED TOMOGRAPHY
,
conjugate gradient methods
,
covariance matrices
,
DECOMPOSITION
,
Density measurement
,
Digital computing or data processing equipment or methods, specially adapted for specific applications
,
dual‐energy CT
,
edge detection
,
edge predetection
,
General statistical methods
,
Head - diagnostic imaging
,
Image data processing or generation, in general
,
image denoising
,
Image enhancement or restoration, e.g. from bit‐mapped to bit‐mapped creating a similar image
,
IMAGE PROCESSING
,
Image Processing, Computer-Assisted - methods
,
image resolution
,
image‐domain decomposition
,
INHIBITION
,
ITERATIVE METHODS
,
LEAST SQUARE FIT
,
least squares approximations
,
matrix inversion
,
Matrix theory
,
Medical image noise
,
medical image processing
,
Medical image reconstruction
,
Medical image smoothing
,
Medical image spatial resolution
,
Medical imaging
,
Medical X‐ray imaging
,
Noise
,
noise suppression
,
Numerical linear algebra
,
PHANTOMS
,
Phantoms, Imaging
,
RADIOLOGY AND NUCLEAR MEDICINE
,
SIGNAL-TO-NOISE RATIO
,
SMOOTH MANIFOLDS
,
SPATIAL RESOLUTION
,
Tomography, X-Ray Computed - methods
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