Evaluation of noise power spectra of CT images

Metheany, Kathrine G.; Kwan, Alexander L. C.; Boone, John M.

doi:10.1117/12.708308

Cited by 3 publications

(3 citation statements)

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“…This section was used to evaluate noise frequency characteristics, for which NPS with reference to other research regarding CT image noise characteristics was used [24][25][26]. …”

Section: Evaluation Using a Cylindrical Test Phantommentioning

confidence: 99%

Development of DICOM image-based CT low dose simulator using fan-beam transform

Horiuchi

Yamamoto²,

Murase

2013

THC

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BACKGROUND: Projection-data based method is established as an accurate simulation of low-dose CT, but cooperation of the CT manufacturer is required. Image-based method is awaited for independent and efficient research. OBJECTIVE: To develop and verify image-based method for adding noise to DICOM images. METHODS: This technique reproduces projection data by fan-beam transform of the DICOM image data and by creating and reconstructing noise projections into a noise image that can be added to the original image. A cylindrical test phantom and anthropomorphic phantom were used to verify the simulation method for both standard and adaptive iterative reconstruction methods. RESULTS: The simulated images compared favorably with actual images. Standard deviation difference of the simulated images were 1.27% ± 0.81% (cylindrical phantom) and ranged from 1.61% ± 0.81% (head), to 5.41% ± 1.57% (hepatic portal region) (anthropomorphic phantom). The standard deviation difference of the cylindrical phantom with the adaptive iterative technique were 3.41% ± 1.76% at 50% ASIR and 3.85% ± 1.82% at 100% ASIR. The simulated noise power spectra of both types of images were comparable to the actual images. CONCLUSION: We developed and validated a DICOM image-based low-dose simulation that allows researchers to perform dose reduction research independently and efficiently.

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“…This section was used to evaluate noise frequency characteristics, for which NPS with reference to other research regarding CT image noise characteristics was used [24][25][26]. …”

Section: Evaluation Using a Cylindrical Test Phantommentioning

confidence: 99%

Development of DICOM image-based CT low dose simulator using fan-beam transform

Horiuchi

Yamamoto²,

Murase

2013

THC

View full text Add to dashboard Cite

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“…9,10 Many NPS studies have been conducted in the past to assess the noise characteristics of clinical CT systems. [11][12][13] Traditionally, the NPS is estimated by ensemble averaging multiple realizations of noise-only images. 14 However, the estimation error increases when there are a limited number of images.…”

Section: Introductionmentioning

confidence: 99%

“…The NPS plays a key role in image quality (IQ) evaluation as it can be used for predicting detection performance 6–8 or calculating detective quantum efficiency (DQE) 9,10 . Many NPS studies have been conducted in the past to assess the noise characteristics of clinical CT systems 11–13 …”

Section: Introductionmentioning

confidence: 99%

Method to estimate fan‐beam CT noise power spectrum using two basis functions with a limited number of noise realizations

Jang

Baek

2022

Medical Physics

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Purpose The noise power spectrum (NPS) plays a key role in image quality (IQ) evaluation as it can be used for predicting detection performance or calculating detective quantum efficiency (DQE). Traditionally, the NPS is estimated by ensemble averaging multiple realizations of noise‐only images. However, the estimation error increases when there are a limited number of images. Since the estimation error directly affects the image quality (IQ) index, an accurate NPS estimation method is required. Recent works have proposed NPS estimation methods using the radial one‐dimensional (1D) NPS as the basis; however, when sharp kernels are used during image reconstruction, these methods cannot accurately estimate the amplitude of each angular spoke of the 2D NPS composed of different cutoff frequencies determined from the complementary projection magnification factors for different spatial regions. In this work, we propose a 2D NPS estimation method that reflects the accurate amplitude of each angular spoke for fan‐beam CT images. Methods An angular spoke of the 2D NPS is composed of two basis functions with different cutoff frequencies determined from the complementary projection magnification factors. The proposed method estimates these two weighting factors for each basis function by minimizing the mean‐squared error (MSE) between the 2D NPS estimated from 10 noise realizations. Two noise profiles and two types of apodization filters (i.e., rectangular and Hanning) were used to reconstruct the noise‐only images. To examine the nonstationary noise property of fan‐beam CT images, the 2D NPS was estimated at three different local regions. The estimation accuracy of the proposed method was further improved by estimating the approximate weighting factors with sinusoidal functions, considering that the weighting factors vary slowly throughout the view angles. Regression orders of 1 to 4 were used during these estimations. The approximate weighting factors were then multiplied with each of the basis functions to estimate the 2D NPS. The normalized mean‐squared error (NMSE) was used as an index to compare the performance of each NPS estimation method, with the analytical 2D NPS as the reference. Further validation was performed using XCAT phantom data. Results We observed that the 2D NPS estimated using two basis functions reflected the accurate amplitude of each angular spoke, whereas the 2D NPS estimated using the radial 1D NPS as the basis could not. The 2D NPS estimated by applying the approximate weighting factors showed improved performance compared with that estimated using two basis functions. In addition, unlike the view‐independent noise cases, where a lower regression order showed higher estimation performance, a higher regression order showed higher estimation performance in the view‐dependent noise cases. Conclusions In this work, we propose a 2D NPS estimation method that reflects the accurate amplitude of each angular spoke for fan‐beam CT images using two basis functions. We observed that the proposed ...

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