An alternative solution to the nonuniform noise propagation problem in fan‐beam FBP image reconstruction

Wang, Jing; Lu, Hongbing; Li, Tianfang; Zhang, Liang

doi:10.1118/1.2064807

Cited by 25 publications

(11 citation statements)

References 5 publications

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“…In order to avoid the non-uniform noise propagation problem in fan-beam geometry, the intersecting area of fan-beam strip and square image pixel was used as the weight, rather than a bi-linear interpolation, in the backprojection step in the FBP algorithm [22]. The non-uniform noise propagation problem in fan-beam CT is believed to be caused by the distance-dependent factor 1/ L 2 in fan-beam FBP reconstruction [23][24].…”

Section: Methodsmentioning

confidence: 99%

Virtual Colonoscopy Screening With Ultra Low-Dose CT and Less-Stressful Bowel Preparation: A Computer Simulation Study

Wang

et al. 2008

IEEE Trans. Nucl. Sci.

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Computed tomography colonography (CTC) or CT-based virtual colonoscopy (VC) is an emerging tool for detection of colonic polyps. Compared to the conventional fiber-optic colonoscopy, VC has demonstrated the potential to become a mass screening modality in terms of safety, cost, and patient compliance. However, current CTC delivers excessive X-ray radiation to the patient during data acquisition. The radiation is a major concern for screening application of CTC. In this work, we performed a simulation study to demonstrate a possible ultra low-dose CT technique for VC. The ultra low-dose abdominal CT images were simulated by adding noise to the sinograms of the patient CTC images acquired with normal dose scans at 100 mAs levels. The simulated noisy sinogram or projection data were first processed by a Karhunen-Loève domain penalized weighted least-squares (KL-PWLS) restoration method and then reconstructed by a filtered backprojection algorithm for the ultra low-dose CT images. The patient-specific virtual colon lumen was constructed and navigated by a VC system after electronic colon cleansing of the orally-tagged residue stool and fluid. By the KL-PWLS noise reduction, the colon lumen can successfully be constructed and the colonic polyp can be detected in an ultra low-dose level below 50 mAs. Polyp detection can be found more easily by the KL-PWLS noise reduction compared to the results using the conventional noise filters, such as Hanning filter. These promising results indicate the feasibility of an ultra low-dose CTC pipeline for colon screening with less-stressful bowel preparation by fecal tagging with oral contrast.

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Section: Methodsmentioning

confidence: 99%

Virtual Colonoscopy Screening With Ultra Low-Dose CT and Less-Stressful Bowel Preparation: A Computer Simulation Study

Wang

et al. 2008

IEEE Trans. Nucl. Sci.

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“…19 and 20 and several approaches to reduce the nonstationarity were proposed in Refs. [21][22][23]. The NPS of a cone beam CT system was studied in Refs.…”

Section: Introductionmentioning

confidence: 99%

The noise power spectrum in CT with direct fan beam reconstruction

Baek

Pelc

2010

Medical Physics

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The noise power spectrum ͑NPS͒ is a useful metric for understanding the noise content in images. To examine some unique properties of the NPS of fan beam CT, the authors derived an analytical expression for the NPS of fan beam CT and validated it with computer simulations. The nonstationary noise behavior of fan beam CT was examined by analyzing local regions and the entire field-of-view ͑FOV͒. This was performed for cases with uniform as well as nonuniform noise across the detector cells and across views. The simulated NPS from the entire FOV and local regions showed good agreement with the analytically derived NPS. The analysis shows that whereas the NPS of a large FOV in parallel beam CT ͑using a ramp filter͒ is proportional to frequency, the NPS with direct fan beam FBP reconstruction shows a high frequency roll off. Even in small regions, the fan beam NPS can show a sharp transition ͑discontinuity͒ at high frequencies. These effects are due to the variable magnification and therefore are more pronounced as the fan angle increases. For cases with nonuniform noise, the NPS can show the directional dependence and additional effects.

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“…Figure 5 shows the reconstruction of the object function f (x, y), which is obtained by the two dimensional fast inverse Fourier transform of the Eq. (34).…”

Section: Simulation Results and Generalized Fourier Slice Theoremmentioning

confidence: 99%

Fan beam image reconstruction with generalized fourier slice theorem

Zhao¹,

Yang²,

Yang³

2014

Journal of X-Ray Science and Technology: Clinical Applications

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For parallel beam geometry the Fourier reconstruction works via the Fourier slice theorem (or central slice theorem, projection slice theorem). For fan beam situation, Fourier slice can be extended to a generalized Fourier slice theorem (GFST) for fan-beam image reconstruction. We have briefly introduced this method in a conference. This paper reintroduces the GFST method for fan beam geometry in details. The GFST method can be described as following: the Fourier plane is filled by adding up the contributions from all fanbeam projections individually; thereby the values in the Fourier plane are directly calculated for Cartesian coordinates such avoiding the interpolation from polar to Cartesian coordinates in the Fourier domain; inverse fast Fourier transform is applied to the image in Fourier plane and leads to a reconstructed image in spacial domain. The reconstructed image is compared between the result of the GFST method and the result from the filtered backprojection (FBP) method. The major differences of the GFST and the FBP methods are: (1) The interpolation process are at different data sets. The interpolation of the GFST method is at projection data. The interpolation of the FBP method is at filtered projection data.(2) The filtering process are done in different places. The filtering process of the GFST is at Fourier domain. The filtering process of the FBP method is the ramp filter which is done at projections. The resolution of ramp filter is variable with different location but the filter in the Fourier domain lead to resolution invariable with location. One advantage of the GFST method over the FBP method is in short scan situation, an exact solution can be obtained with the GFST method, but it can not be obtained with the FBP method. The calculation of both the GFST and the FBP methods are at O(N 3 ), where N is the number of pixel in one dimension.

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An alternative solution to the nonuniform noise propagation problem in fan‐beam FBP image reconstruction

Cited by 25 publications

References 5 publications

Virtual Colonoscopy Screening With Ultra Low-Dose CT and Less-Stressful Bowel Preparation: A Computer Simulation Study

Virtual Colonoscopy Screening With Ultra Low-Dose CT and Less-Stressful Bowel Preparation: A Computer Simulation Study

The noise power spectrum in CT with direct fan beam reconstruction

Fan beam image reconstruction with generalized fourier slice theorem

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