Improved image quality of helical computed tomography of the head in children by iterative reconstruction

Ono, Shun; Niwa, Tetsu; Yanagimachi, Noriharu; Yamashita, Tomohiro; Okazaki, Takashi; Nomura, Takakiyo; Hashimoto, Jun; Imai, Yutaka

doi:10.1016/j.neurad.2015.07.005

Cited by 8 publications

(6 citation statements)

References 20 publications

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“…The current research findings support a preference for low iteration strengths as reported in some abdominal and cranial studies [29][30][31]. Numerous other authors [1,6,27,[32][33][34][35] report the use of higher iteration strengths without loss of demarcation across multiple anatomic areas. There may be a number of reasons for opinion variation including the CT system used, the Table 2 for exposure protocol and image randomization numbers.…”

Section: Discussionsupporting

confidence: 84%

The Acceptability of Iterative Reconstruction Algorithms in Head CT: An Assessment of Sinogram Affirmed Iterative Reconstruction (SAFIRE) vs. Filtered Back Projection (FBP) Using Phantoms

Harris

Huckle

Anthony

et al. 2017

Journal of Medical Imaging and Radiation Sciences

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Background: Computed tomography (CT) is the primary imaging investigation for many neurologic conditions with a proportion of patients incurring cumulative doses. Iterative reconstruction (IR) allows dose optimization, but head CT presents unique image quality complexities and may lead to strong reader preferences. Objectives: This study evaluates the relationships between image quality metrics, image texture, and applied radiation dose within the context of IR head CT protocol optimization in the simulated patient setting. A secondary objective was to determine the influence of optimized protocols on diagnostic confidence using a custom phantom. Methods and Setting: A three-phase phantom study was performed to characterize reconstruction methods at the local reference standard and a range of exposures. CT numbers and pixel noise were quantified supplemented by noise uniformity, noise power spectrum, contrast-to-noise ratio (CNR), high-and low-contrast resolution. Reviewers scored optimized protocol images based on established reporting criteria. Results: Increasing strengths of IR resulted in lower pixel noise, lower noise variance, and increased CNR. At the reference standard, the image noise was reduced by 1.5 standard deviation and CNR increased by 2.0. Image quality was maintained at 24% relative dose reduction. With the exception of image sharpness, there were no significant differences between grading for IR and filtered back projection reconstructions. Conclusions: IR has the potential to influence pixel noise, CNR, and noise variance (image texture); however, systematically optimized IR protocols can maintain the image quality of filtered back projection. This work has guided local application and acceptance of lower dose head CT protocols.

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Section: Discussionsupporting

confidence: 84%

The Acceptability of Iterative Reconstruction Algorithms in Head CT: An Assessment of Sinogram Affirmed Iterative Reconstruction (SAFIRE) vs. Filtered Back Projection (FBP) Using Phantoms

Harris

Huckle

Anthony

et al. 2017

Journal of Medical Imaging and Radiation Sciences

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“…Utilizing a CT technique justified by recent literature, and by using a previously published robust method of subjectively and objectively assessing image quality, this study demonstrates that there is no significant difference in subjective image quality between studies of the equine head performed with a tube current of 300, 225, or 150 mAs. Subjective scores indicated little difference in proportions of binary score 1 between 225 and 300 mAs.…”

Section: Discussionmentioning

confidence: 70%

“…This was performed by an unblinded veterinary radiology resident (T.D.). Mean and standard deviation (SD) values were used to calculate signal‐to‐noise ratio (SNR) and contrast‐to‐noise ratio (CNR) using the following equations, consistent with previous publications:

SNR = normalMean normalH {normalU}_{normalROI} / S {normalD}_{normalROI}

CNR = {((), mean H U_{LE} - mean H U_{normalMM false)} / ([], (S {D_{LE}}^{2} + S {D_{MM}}^{2})))}^{1 / 2}

…”

Section: Methodsmentioning

confidence: 99%

Standing CT of the equine head: Reducing radiation dose maintains image quality

Davies

Skelly

Puggioni

et al. 2019

Vet Radiology Ultrasound

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Multiple published studies involving computed tomographic (CT) examinations of the equine head utilise a wide range of mAs parameters for image acquisition. This prospective, experimental study assessed the effects of lowering mAs during CT image acquisition on image quality and scatter radiation on 10 cadaver equine heads. Each head was scanned three times at 300, 225, and 150 mAs, with all other scanning parameters remaining constant between series. An anthropomorphic phantom was positioned adjacent to each equine head during image acquisition, mimicking a human bystander, with an ionization chamber attached to the phantom at eye level. Each series was reconstructed using filtered back projection, using medium (H30) and high (H80) frequency reconstruction algorithms. Quantitative image quality assessment was performed by calculating signal to noise ratio (SNR) and contrast to noise ratio (CNR). Two qualitative image quality assessments were performed independently by three blinded board certified veterinary radiologists with a 4 week interval, using a visual grade analysis model adapted from peer reviewed medical literature. Ionization chamber measurements, calculated volume CT dose index (CTDIvol), and dose‐length product (DLP) were recorded. Halving radiation dose during image acquisition from 300 to 150mAs resulted in comparable image quality between series. There was a statistically significant and linear relationship between mAs and scatter radiation to the bystander; halving mAs during image acquisition resulted in halving of scatter radiation. Results of this cadaveric study support the use of lower mAs settings during standing CT examinations of the equine head.

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“…There are two main types of tomographic algorithms: analytical algorithms and iterative algorithms. The analytic algorithms are based on solving the integral equation in the continuous form, while the iterative algorithms focus on solving linear equations of the forward model in the discrete form [8,9]. Filtered Back Projection (FBP) is representative of the analytical algorithm in 2D scanning mode.…”

Section: Introductionmentioning

confidence: 99%

Ordered Subset Expectation Maximum Algorithms Based on Symmetric Structure for Image Reconstruction

Liu

Qiu

2018

Symmetry

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In this paper, we propose the symmetric structure of the reconstructed points discretization model to partition and order the subsets of Ordered Subset Expectation Maximum (OSEM) algorithms for image reconstruction and then simplify the calculation of the projection coefficient matrix while satisfying the balancing properties of subsets. The reconstructed points discretization model was utilized to describe the forward and inverse relationships between the reconstructed points and the projection data according to the distance from the point to the ray rather than the intersection length between the square pixel and the ray. This discretization model provides new approaches for improving and constructing the reconstruction algorithms on the basis of the geometry of the model. The experimental results show that the OSEM algorithms based on the reconstructed points discretization model and its geometric symmetry structure can effectively improve the imaging speed and the imaging precision.

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Improved image quality of helical computed tomography of the head in children by iterative reconstruction

Cited by 8 publications

References 20 publications

The Acceptability of Iterative Reconstruction Algorithms in Head CT: An Assessment of Sinogram Affirmed Iterative Reconstruction (SAFIRE) vs. Filtered Back Projection (FBP) Using Phantoms

The Acceptability of Iterative Reconstruction Algorithms in Head CT: An Assessment of Sinogram Affirmed Iterative Reconstruction (SAFIRE) vs. Filtered Back Projection (FBP) Using Phantoms

Standing CT of the equine head: Reducing radiation dose maintains image quality

Ordered Subset Expectation Maximum Algorithms Based on Symmetric Structure for Image Reconstruction

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