Improvement of Image Quality in Unenhanced Dual-Layer CT of the Head Using Virtual Monoenergetic Images Compared With Polyenergetic Single-Energy CT

Neuhaus, Victor; Abdullayev, Nuran; Hokamp, Nils Große; Pahn, Gregor; Kabbasch, Christoph; Mpotsaris, Anastasios; Maintz, David; Borggrefe, Jan

doi:10.1097/rli.0000000000000367

Cited by 66 publications

(81 citation statements)

References 29 publications

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“…A number of studies have been conducted on the dual‐layer technology, primarily looking at applications of dual‐energy analysis . However, only few studies have yet been published on image quality of conventional images acquired on the IQon .…”

Section: Discussionmentioning

confidence: 99%

“…A number of studies have been conducted on the duallayer technology, primarily looking at applications of dualenergy analysis. 5,[9][10][11][12][13][14][15] However, only few studies have yet been published on image quality of conventional images acquired on the IQon. 16 In general, the conventional images acquired on the IQon are very similar to images acquired on the iCT, as can be seen in Fig.…”

Section: Discussionmentioning

confidence: 99%

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Image quality of conventional images of dual‐layer SPECTRAL CT: A phantom study

et al. 2018

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Purpose: Spectral CT using a dual layer detector offers the possibility of retrospectively introducing spectral information to conventional CT images. In theory, the dual-layer technology should not come with a dose or image quality penalty for conventional images. In this study, we evaluate the influence of a dual-layer detector (IQon Spectral CT, Philips Healthcare) on the image quality of conventional CT images, by comparing these images with those of a conventional but otherwise technically comparable single-layer CT scanner (Brilliance iCT, Philips Healthcare), by means of phantom experiments. Methods: For both CT scanners, conventional CT images were acquired using four adult scanning protocols: (a) body helical, (b) body axial, (c) head helical, and (d) head axial. A CATPHAN 600 phantom was scanned to conduct an assessment of image quality metrics at equivalent (CTDI) dose levels. Noise was characterized by means of noise power spectra (NPS) and standard deviation (SD) of a uniform region, and spatial resolution was evaluated with modulation transfer functions (MTF) of a tungsten wire. In addition, contrast-to-noise ratio (CNR), image uniformity, CT number linearity, slice thickness, slice spacing, and spatial linearity were measured and evaluated. Additional measurements of CNR, resolution and noise were performed in two larger phantoms. Results: The resolution levels at 50%, 10%, and 5% MTF of the iCT and IQon showed small, but significant differences up to 0.25 lp/cm for body scans, and up to 0.2 lp/cm for head scans in favor of the IQon. The iCT and IQon showed perfect CT linearity for body scans, but for head scans both scanners showed an underestimation of the CT numbers of materials with a high opacity. Slice thickness was slightly overestimated for both scanners. Slice spacing was comparable and reconstructed correctly. In addition, spatial linearity was excellent for both scanners, with a maximum error of 0.11 mm. CNR was higher on the IQon compared to the iCT for both normal and larger phantoms with differences up to 0.51. Spatial resolution did not change with phantom size, but noise levels increased significantly. For head scans, IQon had a noise level that was significantly lower than the iCT, on the other hand IQon showed noise levels significantly higher than the iCT for body scans. Still, these differences were well within the specified range of performance of iCT scanners. Conclusions: At equivalent dose levels, this study showed similar quality of conventional images acquired on iCT and IQon for medium-sized phantoms and slightly degraded image quality for (very) large phantoms at lower tube voltages on the IQon. Accordingly, it may be concluded that the introduction of a dual-layer detector neither compromises image quality of conventional images nor increases radiation dose for normal-sized patients, and slightly degrades dose efficiency for large patients at 120 kVp and lower tube voltages.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Image quality of conventional images of dual‐layer SPECTRAL CT: A phantom study

et al. 2018

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“…Furthermore, their method to obtain this diagnostic equation combining ICs from both non‐enhanced and contrast‐enhanced CT images inevitably doubled the patients' radiation exposure. In this study, we used a recently implemented DECT scanner, which only a few studies used . This scanner achieves spectral separation using a different method from the previous fast‐kVp switching scanner in which the X‐ray tube rapidly modulates tube voltage .…”

Section: Discussionmentioning

confidence: 99%

“…In this study, we used a recently implemented DECT scanner, which only a few studies used. [30][31][32][33][34][35] This scanner achieves spectral separation using a different method from the previous fast-kVp switching scanner in which the X-ray tube rapidly modulates tube voltage. 7,8,10 In contrast, our DECT scanner built with 2 scintillating layers has a single X-ray source that operates at a fixed tube potential, typically 120 or 140 kVp.…”

Section: Discussionmentioning

confidence: 99%

Dual‐energy CT iodine quantification for characterizing focal thyroid lesions

Lee

Seo

et al. 2018

Head & Neck

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Background To determine the usefulness of dual‐energy CT (DECT) iodine quantification to classify the focal thyroid lesions. Methods We retrospectively enrolled a total of 76 cytopathologically confirmed focal thyroid lesions (mean size: 1.9 cm). After drawing a region of interest on the DECT‐derived iodine maps, the obtained iodine concentration values of thyroid nodules (IC_N) and normalized IC_N were compared between 3 groups: papillary thyroid carcinoma (PTC), benign nodule, and cyst. Results From all lesions, 46, 17, and 13 were assigned to the PTC, benign nodule, and cyst groups. IC_N was the highest in the benign nodule, lower in the PTC, and the lowest in the cyst (median [interquartile range]: 4.3 [3.13‐5.48], 3.15 [2.29‐4.01], 0.60 [0.33‐0.88], all P < .001). Similarly, the normalized IC_N values were all statistically different from each other (P < .05).The multi‐class area under the curves using the optimal cutoff values were 0.931 for IC_N and 0.918, 0.920 for normalized IC, respectively. Conclusion DECT iodine quantification could be helpful to classify the focal thyroid lesions.

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“…A benefit of projection space decomposition is the intrinsic reduction in beam hardening artifacts. A reduction in beam hardening artifacts on virtual monoenergetic images created from dual-layer spectral CT data compared to conventional images has been demonstrated for head imaging, 25 myocardial perfusion imaging, 27 coronary stent imaging, 28 and imaging of hip prostheses. 29 This registration of spectral data also allows the identification and removal of anti-correlated noise in basis material raw data sets, facilitating noise suppression while preserving signal.…”

Section: A1 Dual-layer Detectorsmentioning

confidence: 99%

Principles and applications of multienergy CT: Report of AAPM Task Group 291

McCollough

Boedeker

Cody³

et al. 2020

Medical Physics

138

195

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In x-ray computed tomography (CT), materials with different elemental compositions can have identical CT number values, depending on the mass density of each material and the energy of the detected x-ray beam. Differentiating and classifying different tissue types and contrast agents can thus be extremely challenging. In multienergy CT, one or more additional attenuation measurements are obtained at a second, third or more energy. This allows the differentiation of at least two materials. Commercial dual-energy CT systems (only two energy measurements) are now available either using sequential acquisitions of low-and high-tube potential scans, fast tube-potential switching, beam filtration combined with spiral scanning, dual-source, or dual-layer detector approaches. The use of energy-resolving, photon-counting detectors is now being evaluated on research systems. Irrespective of the technological approach to data acquisition, all commercial multienergy CT systems circa 2020 provide dual-energy data. Material decomposition algorithms are then used to identify specific materials according to their effective atomic number and/or to quantitate mass density. These algorithms are applied to either projection or image data. Since 2006, a number of clinical applications have been developed for commercial release, including those that automatically (a) remove the calcium signal from bony anatomy and/or calcified plaque; (b) create iodine concentration maps from contrast-enhanced CT data and/or quantify absolute iodine concentration; (c) create virtual noncontrast-enhanced images from contrast-enhanced scans; (d) identify perfused blood volume in lung parenchyma or the myocardium; and (e) characterize materials according to their elemental compositions, which can allow in vivo differentiation between uric-acid and non-uric-acid urinary stones or uric acid (gout) or non-uric-acid (calcium pyrophosphate) deposits in articulating joints and surrounding tissues. In this report, the underlying physical principles of multienergy CT are reviewed and each of the current technical approaches are described. In addition, current and evolving clinical applications are introduced. Finally, the impact of multienergy CT technology on patient radiation dose is summarized.

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Improvement of Image Quality in Unenhanced Dual-Layer CT of the Head Using Virtual Monoenergetic Images Compared With Polyenergetic Single-Energy CT

Abstract: In comparison to polyenergetic images, virtual monoenergetic images reconstructed from unenhanced DLCT of the head at 65 keV and 120 keV allow to optimize gray-white matter contrast and reduce beam hardening artifacts caused by the skull, respectively.

Cited by 66 publications

References 29 publications

Image quality of conventional images of dual‐layer SPECTRAL CT: A phantom study

Image quality of conventional images of dual‐layer SPECTRAL CT: A phantom study

Dual‐energy CT iodine quantification for characterizing focal thyroid lesions

Principles and applications of multienergy CT: Report of AAPM Task Group 291

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