Image quality evaluation of dual-layer spectral detector CT of the chest and comparison with conventional CT imaging

Doerner, Jonas; Hauger, Myriam; Hickethier, Tilman; Byrtus, Jonathan; Wybranski, Christian; Hokamp, Nils Große; Maintz, David; Haneder, Stefan

doi:10.1016/j.ejrad.2017.05.016

Cited by 60 publications

(47 citation statements)

References 20 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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“…This technology allows the acquisition of energy-selective projection data in the two detection layers simultaneously and therefore directly generating spectral information for each CT scan without the need to select specific protocols [ 8 ]. Compared with DSCT, DLCT seems to be superior in generating highly accurate virtual monoenergetic images (VMIs) [ 9 , 10 ] to recognise different materials and to quantitate elemental decompositions, such as intravenous contrast agents or bone mineral density [ 11 – 13 ], which may be of great benefit when estimating electron densities.…”

Section: Introductionmentioning

confidence: 99%

Dual-layer spectral computed tomography: measuring relative electron density

et al. 2018

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BackgroundX-ray and particle radiation therapy planning requires accurate estimation of local electron density within the patient body to calculate dose delivery to tumour regions. We evaluate the feasibility and accuracy of electron density measurement using dual-layer computed tomography (DLCT), a recently introduced dual-energy CT technique.MethodsTwo calibration phantoms were scanned with DLCT and virtual monoenergetic images (VMIs) at 50 keV and 200 keV were generated. We investigated two approaches to obtain relative electron densities from these VMIs: to fit an analytic interaction cross-sectional model and to empirically calibrate a conversion function with one of the phantoms. Knowledge of the emitted x-ray spectrum was not required for the presented work.ResultsThe results from both methods were highly correlated to the nominal values (R > 0.999). Except for the water and lung inserts, the error was within 1.79% (average 1.53%) for the cross-sectional model and 1.61% (average 0.87%) for the calibrated conversion. Different radiation doses did not have a significant influence on the measurement (p = 0.348, 0.167), suggesting that the methods are reproducible. Further, we applied these methods to routine clinical data.ConclusionsOur study shows a high validity of electron density estimation based on DLCT, which has potential to improve the procedure and accuracy of measuring electron density in clinical practice.

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“…In iodine contrast-enhanced CT, virtual monoenergetic images at 40 keV (hereafter, VMI 40keV ) result in greater iodine attenuation due to imaging near k-edge of iodine (33.3 keV), resulting in a higher x-ray absorption. Low-kiloelectron volt imaging with CT enhances vessel contrast, image quality, and the detection of hypervascularized lesions (18)(19)(20)(21). Previous studies have shown that iodine overlay (IO) images hold the potential for an improved detection of occult metastases (22).…”

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confidence: 99%

Dual-Energy CT–derived Iodine Maps: Use in Assessing Pleural Carcinomatosis

Lennartz¹,

Blanc

Zopfs

et al. 2019

Radiology

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To evaluate the use of spectral CT for differentiation between noncalcified benign pleural lesions and pleural carcinomatosis. Materials and Methods: In this retrospective study, patients who underwent contrast agent-enhanced late venous phase spectral CT of the chest between June 1, 2016, and July 1, 2018 with histopathologic and/or imaging confirmation of noncalcified pleural lesions were evaluated. Conventional images, iodine overlay (IO) images, and virtual monoenergetic images at 40 keV (hereafter, VMI 40keV) were reconstructed from contrast-enhanced spectral chest CT. Four blinded radiologists determined lesion presence and indicated lesion conspicuity and diagnostic certainty. Hounsfield unit attenuation from conventional images and iodine concentration (IC) (in milligrams per milliliter) from IO images were determined. Area under the receiver operating characteristics curve determined thresholds for quantitative lesion differentiation and cutoff values were validated in an independent data set. Results: Eighty-four patients were included (mean age, 66.2 years; 54 men and 30 women; 44 patients with cancer with confirmed pleural carcinomatosis and 40 patients with benign pleural lesions). The area under the receiver operating characteristics curve for IC was greater than that of conventional Hounsfield units (0.96 vs 0.91; P  .05, respectively). The optimal IC threshold was 1.3 mg/mL, with comparable sensitivity and specificity when applied to the test data set. The sensitivities to depict pleural carcinomatosis with spectral reconstructions versus conventional CT were 96% (199 of 208) and 83% (172 of 208), respectively, with specificities of 84% (161 of 192) and 63% (120 of 192), respectively (P  .001 each). Conclusion: Compared with conventional images, spectral CT with iodine maps improved both quantitative and qualitative determination of pleural carcinomatosis versus noncalcified benign pleural lesions.

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Image quality evaluation of dual-layer spectral detector CT of the chest and comparison with conventional CT imaging

Cited by 60 publications

References 20 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-layer spectral computed tomography: measuring relative electron density

Dual-Energy CT–derived Iodine Maps: Use in Assessing Pleural Carcinomatosis

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