Contrast-to-Noise Ratio and Low-Contrast Object Resolution on Full- and Low-Dose MDCT: SAFIRE Versus Filtered Back Projection in a Low-Contrast Object Phantom and in the Liver

Baker, Mark E.; Dong, Frank; Primak, Andrew N.; Obuchowski, Nancy A.; Einstein, David M.; Gandhi, Namita; Herts, Brian R.; Purysko, Andrei S.; Remer, Erick M.; Vachani, Neil

doi:10.2214/ajr.11.7421

Cited by 155 publications

(126 citation statements)

References 43 publications

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“…streaking) are preserved [15,26,27]. It is of particular interest, therefore, that, although noise reductions have been shown here by the hybrid algorithm consistent with previous studies [15,[27][28][29][30][31], this noise benefit does not necessarily translate to an improvement in low-contrast object detection, even though conservation of noise textures [26,28], enhanced lesion conspicuity [27,[32][33][34] and improved image quality [15,24,[34][35][36] have all been reported with hybrid FBP/iterative methods compared with standard FBP reconstruction. This may be explained in part by the fact that iDose 4 uses FBP for its initial estimate, and, consequently, the B and iDose 4 algorithms will produce similar covariance properties resulting in similar performance for low-contrast lesion detection [37][38][39].…”

Section: Discussionsupporting

confidence: 84%

“…Hybrid approaches that combine an abbreviated form of iterative reconstruction with FBP offer a potential time-effective solution where noise is reduced, important image boundaries maintained and the familiar visual properties (e.g. streaking) are preserved [15,26,27]. It is of particular interest, therefore, that, although noise reductions have been shown here by the hybrid algorithm consistent with previous studies [15,[27][28][29][30][31], this noise benefit does not necessarily translate to an improvement in low-contrast object detection, even though conservation of noise textures [26,28], enhanced lesion conspicuity [27,[32][33][34] and improved image quality [15,24,[34][35][36] have all been reported with hybrid FBP/iterative methods compared with standard FBP reconstruction.…”

Section: Discussionmentioning

confidence: 99%

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Noise-reducing algorithms do not necessarily provide superior dose optimisation for hepatic lesion detection with multidetector CT

Dobeli¹,

Lewis²,

Meikle³

et al. 2013

The British Journal of Radiology

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Cite this article as: Dobeli KL, Lewis SJ, Meikle SR, Thiele DL, Brennan PC. Noise-reducing algorithms do not necessarily provide superior dose optimisation for hepatic lesion detection with multidetector CT. Br J Radiol 2013;86:20120500. Noise-reducing algorithms do not necessarily provide superior dose optimisation for hepatic lesion detection with multidetector CT Objective:To compare the doseoptimisation potential of a smoothing filtered backprojection (FBP) and a hybrid FBP/iterative algorithm to that of a standard FBP algorithm at three slice thicknesses for hepatic lesion detection with multidetector CT.Methods: A liver phantom containing a 9.5-mm opacity with a density of 10 HU below background was scanned at 125, 100, 75, 50 and 25 mAs. Data were reconstructed with standard FBP (B), smoothing FBP (A) and hybrid FBP/iterative (iDose 4 ) algorithms at 5-, 3-and 1-mm collimation. 10 observers marked opacities using a four-point confidence scale. Jackknife alternative freeresponse receiver operating characteristic figure of merit (FOM), sensitivity and noise were calculated.Results: Compared with the 125-mAs/5-mm setting for each algorithm, significant reductions in FOM (p,0.05) and sensitivity (p,0.05) were found for all three algorithms for all exposures at 1-mm thickness and for all slice thicknesses at 25 mAs, with the exception of the 25-mAs/5-mm setting for the B algorithm. Sensitivity was also significantly reduced for all exposures at 3-mm thickness for the A algorithm (p,0.05). Noise for the A and iDose 4 algorithms was approximately 13% and 21% lower, respectively, than for the B algorithm.Conclusion: Superior performance for hepatic lesion detection was not shown with either a smoothing FBP algorithm or a hybrid FBP/iterative algorithm compared with a standard FBP technique, even though noise reduction with thinner slices was demonstrated with the alternative approaches.

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Section: Discussionsupporting

confidence: 84%

Section: Discussionmentioning

confidence: 99%

Noise-reducing algorithms do not necessarily provide superior dose optimisation for hepatic lesion detection with multidetector CT

Dobeli¹,

Lewis²,

Meikle³

et al. 2013

The British Journal of Radiology

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“…All statistical iterative reconstruction algorithms achieve significant noise reduction and have been reported to allow dose reductions in the range of 30%-50% while maintaining image quality (21,(29)(30)(31)(32)(33)(34)(35)(36). With ASIR (GE Healthcare), SAFIRE (Siemens Healthcare), and iDose (Philips Healthcare) (4), the degree of noise reduction on the final image can be customized with userselected levels.…”

Section: Statistical Iterative Reconstructionmentioning

confidence: 99%

“…The diagnostic accuracy when evaluating objects with high contrast (such as renal calculi at CT angiography) is only minimally affected with use of low-dose protocols, whereas it is more adversely affected when evaluating objects with low contrast (such as hepatic metastasis). This holds true even when iterative image reconstruction is applied, such that even though the measured image noise would remain constant with low-dose protocols, lesion detectability would be reduced with use of aggressive dose reduction techniques (32). The optimal dose reduction achieved with iterative image reconstruction depends on the imaging task and should not be based solely on the goal of reducing image noise.…”

Section: Ct Dose Reduction and Maintenance Of Diagnostic Accuracymentioning

confidence: 99%

Emerging Techniques for Dose Optimization in Abdominal CT

Kaza¹,

Platt²,

Goodsitt

et al. 2014

RadioGraphics

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Recent advances in computed tomographic (CT) scanning technique such as automated tube current modulation (ATCM), optimized x-ray tube voltage, and better use of iterative image reconstruction have allowed maintenance of good CT image quality with reduced radiation dose. ATCM varies the tube current during scanning to account for differences in patient attenuation, ensuring a more homogeneous image quality, although selection of the appropriate image quality parameter is essential for achieving optimal dose reduction. Reducing the x-ray tube voltage is best suited for evaluating iodinated structures, since the effective energy of the x-ray beam will be closer to the k-edge of iodine, resulting in a higher attenuation for the iodine. The optimal kilovoltage for a CT study should be chosen on the basis of imaging task and patient habitus. The aim of iterative image reconstruction is to identify factors that contribute to noise on CT images with use of statistical models of noise (statistical iterative reconstruction) and selective removal of noise to improve image quality. The degree of noise suppression achieved with statistical iterative reconstruction can be customized to minimize the effect of altered image quality on CT images. Unlike with statistical iterative reconstruction, model-based iterative reconstruction algorithms model both the statistical noise and the physical acquisition process, allowing CT to be performed with further reduction in radiation dose without an increase in image noise or loss of spatial resolution. Understanding these recently developed scanning techniques is essential for optimization of imaging protocols designed to achieve the desired image quality with a reduced dose.

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“…Individually, each has been studied intensively before leading to the clinical application [3][4][5][6][7][8][9][10] . Lower tube voltage can provide better contrast because iodine preferentially absorbs much more photons at low tube voltage, but at lower tube voltage, images can be undesirably noisy [8][9][10][11] .…”

Section: Introductionmentioning

confidence: 99%

Size dependence of inherent image quality of a 2nd generation dual source CT scanner

Zhang

Solomon

Samei

2015

IJDI

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The fast developing CT technologies have complicated the protocol optimization process. Since there are increasing numbers of free parameters that can be adjusted, it is imperative to know exactly how these parameters affect the image quality. This paper examines the effect of varying dose level, tube voltage, reconstruction methods and the AEC function on the CT image quality across different sizes. A size varying phantom, consisting of five cylindrical tiers, was used. To assess the image quality, task transfer function (TTF), noise power spectra (NPS), contrast, and detectability index was computed and compared across sizes. It was found that from small to large size, detectability increased more as the dose increased. When the CTDIvol increased from 0.7 to 22.6 mGy, the detectability for the smallest size section increased by four fold but increased by eight fold for the largest section. Low tube voltage exhibited superior detectability and contrast for all sections, especially for the small size sections, where detectability doubled for the smallest section when tube voltage decreased from 120 kV to 80 kV. TTF curves showed considerable dependence on size, but more pronounced dependence on reconstruction techniques. In conclusion, small size phantoms were affected very differently from large size phantoms by dose levels, reconstruction methods, and tube voltage selection. Low tube voltage and iterative reconstruction technique can deliver superior image quality for small patients. Due to beam hardening and substantially increased noise at low tube voltage for large patients, high tube voltage is still recommended for large patients to retain image quality.

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Contrast-to-Noise Ratio and Low-Contrast Object Resolution on Full- and Low-Dose MDCT: SAFIRE Versus Filtered Back Projection in a Low-Contrast Object Phantom and in the Liver

Abstract: Lower dose scans reconstructed with SAFIRE have a higher CNR. The ability of SAFIRE to improve low-contrast object detection and conspicuity depends on the radiation dose level. At low radiation doses, low-contrast objects are invisible, regardless of reconstruction technique.

Cited by 155 publications

References 43 publications

Noise-reducing algorithms do not necessarily provide superior dose optimisation for hepatic lesion detection with multidetector CT

Noise-reducing algorithms do not necessarily provide superior dose optimisation for hepatic lesion detection with multidetector CT

Emerging Techniques for Dose Optimization in Abdominal CT

Size dependence of inherent image quality of a 2nd generation dual source CT scanner

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