Acceptability of virtual unenhanced CT of the aorta as a replacement for the conventional unenhanced phase

Shaida, Nadeem; Bowden, David J.; Barrett, Tristan; Godfrey, Edmund; Taylor, Abby S.; Winterbottom, Andrew; See, Teik Choon; Lomas, David J.; Shaw, Ashley

doi:10.1016/j.crad.2011.10.023

Cited by 25 publications

(8 citation statements)

References 15 publications

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“…The difference was more pronounced in the proximal part of the aorta and less pronounced in the distal part of aorta and the iliac arteries. This attenuation difference between TNC and VNC was more pronounced in our material than has previously been reported (11,12,16). There are several possible explanations to this difference.…”

Section: Discussionsupporting

confidence: 48%

“…There are several possible explanations to this difference. We used tube voltages of 80/Sn140 kVp compared to 100/Sn140 kVp in previous studies (12,16). Compared to the study of Toepker et al (16), in which a total of 110 mL Iomeron 400 mg I/mL contrast medium was used, we used only 80 mL Omnipaque 300 mg I/mL contrast medium.…”

Section: Discussionmentioning

confidence: 99%

“…It has not been well established if the VNC is of acceptable quality to replace the TNC in aortic CTA (12).…”

Section: Introductionmentioning

confidence: 99%

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Reliability of virtual non-contrast computed tomography angiography: comparing it with the real deal

Lehti

Söderberg

Höglund

et al. 2018

Acta Radiologica Open

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BackgroundComputed tomographic angiography (CTA) may require a non-contrast enhanced dataset for the diagnostic workup. By using dual-energy acquisition, it is possible to obtain a virtual non-contrast-enhanced (VNC) dataset, thereby possibly eliminating the non-contrast acquisition and reducing the radiation dose.PurposeTo compare image quality of VNC images reconstructed from arterial phase dual-energy CTA to true non-contrast (TNC) images, and to assess whether VNC images were of sufficient quality to replace TNC images.Material and methodsThirty consecutive patients with suspected abdominal aortic aneurysm, aortic dissection, or subacute control after EVAR/TEVAR were examined with dual-energy CT (DECT). The examination protocol included a single-energy TNC, DECT arterial phase (80 kV/Sn140 kV), and single-energy in venous phase of the aorta. A VNC dataset was obtained from the DE acquisition from arterial phase scans. Mean attenuation and image noise were measured within regions of interest at three levels in the aorta in TNC and VNC images. Comparison of the TNC and VNC images for artefacts was made side-by-side. Subjective evaluation included overall image quality on a 4-grade scale, and quantitative analysis of algorithm-induced artefacts by two experienced readers.ResultsFor all cases, the aortic attenuation was significantly higher at VNC than at TNC. Image noise measured quantitatively was also significantly higher at VNC than at TNC. Subjective image quality was lower for VNC (mean = 3.1 for VNC, 3.7 = for TNC) but there were no cases rated non-diagnostic.ConclusionVNC images based on arterial phase CTA have significantly higher mean attenuation and higher noise levels compared to TNC.

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Section: Discussionsupporting

confidence: 48%

Section: Discussionmentioning

confidence: 99%

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Reliability of virtual non-contrast computed tomography angiography: comparing it with the real deal

Lehti

Söderberg

Höglund

et al. 2018

Acta Radiologica Open

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“…These data suggest that IRF7 silencing by DNA methylation in tumors could result in suppression of immune-regulatory genes important for the surveillance of tumors by cytotoxic immune mechanisms. Other studies have reported an immune-evasion signature dependent on IRF7 in breast and melanoma [40, 43]. To test if such relation between IRF7 and immune-regulatory genes exist in primary LUAD and LUSC tumors, we analyzed the expression of these genes as a function of IRF7 expression, and its promoter methylation status.…”

Section: Resultsmentioning

confidence: 99%

Alterations of immune response of non-small cell lung cancer with Azacytidine

et al. 2013

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Innovative therapies are needed for advanced Non-Small Cell Lung Cancer (NSCLC). We have undertaken a genomics based, hypothesis driving, approach to query an emerging potential that epigenetic therapy may sensitize to immune checkpoint therapy targeting PD-L1/PD-1 interaction. NSCLC cell lines were treated with the DNA hypomethylating agent azacytidine (AZA – Vidaza) and genes and pathways altered were mapped by genome-wide expression and DNA methylation analyses. AZA-induced pathways were analyzed in The Cancer Genome Atlas (TCGA) project by mapping the derived gene signatures in hundreds of lung adeno (LUAD) and squamous cell carcinoma (LUSC) samples. AZA up-regulates genes and pathways related to both innate and adaptive immunity and genes related to immune evasion in a several NSCLC lines. DNA hypermethylation and low expression of IRF7, an interferon transcription factor, tracks with this signature particularly in LUSC. In concert with these events, AZA up-regulates PD-L1 transcripts and protein, a key ligand-mediator of immune tolerance. Analysis of TCGA samples demonstrates that a significant proportion of primary NSCLC have low expression of AZA-induced immune genes, including PD-L1. We hypothesize that epigenetic therapy combined with blockade of immune checkpoints – in particular the PD-1/PD-L1 pathway – may augment response of NSCLC by shifting the balance between immune activation and immune inhibition, particularly in a subset of NSCLC with low expression of these pathways. Our studies define a biomarker strategy for response in a recently initiated trial to examine the potential of epigenetic therapy to sensitize patients with NSCLC to PD-1 immune checkpoint blockade.

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“…One such scenario is in a multiphasic vascular study that typically includes nonenhanced arterial and venous phase images for evaluation of an endograft, where true nonenhanced images help distinguish high-attenuation tissues or calcifications from iodine (Fig 18). By omitting the nonenhanced phase and instead using virtual nonenhanced images obtained from arterial or venous phase dual-energy data, radiation savings of up to 40% can be achieved (96-100) without compromising diagnostic utility, although there have been reports of decreased attenuation of calcium and stents as well as the appearance of pulsation artifacts (98,101). Further radiation dose savings of up to 64% can be achieved in the detection of endoleaks by eliminating both the dedicated nonenhanced and arterial phases and acquiring only the venous phase dual-energy data.…”

Section: Radiation Dose Savingsmentioning

confidence: 99%

Update on Cardiovascular Applications of Multienergy CT

Kalisz¹,

Halliburton²,

Abbara³

et al. 2017

RadioGraphics

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Advances in scanner technology enabling shorter scan times, improvements in spatial and temporal resolution, and more dose-efficient data reconstruction coupled with rapidly growing evidence from clinical trials have established computed tomography (CT) as an important imaging modality in the evaluation of cardiovascular disorders. Multienergy (or spectral or dual-energy) CT is a relatively recent advance in which attenuation data from different energies are used to characterize materials beyond what is possible at conventional CT. Current technologies for multienergy CT are either source based (ie, dual source, rapid kilovoltage switching, dual spin, and split beam) or detector based (ie, dual layer and photon counting), and material-based decomposition occurs in either image or projection space. In addition to conventional diagnostic images, multienergy CT provides image sets such as iodine maps, virtual nonenhanced, effective atomic number, and virtual monoenergy (VM) images as well as data at the elemental level (CT fingerprinting), which can complement and in some areas overcome the limitations posed by conventional CT methods. In myocardial perfusion imaging, iodine maps improve the sensitivity of perfusion defects, and VM images improve the specificity by decreasing artifacts. Iodine maps are also useful in improving the performance of CT in delayed-enhancement imaging. In pulmonary perfusion imaging, iodine maps enhance the sensitivity of detection of both acute and chronic pulmonary emboli. Low-energy (as measured in kiloelectron volts) VM images allow enhancement of vascular contrast, which can either be used to lower contrast dose or salvage a suboptimal contrast-enhanced study. High-energy VM images can be used to decrease or eliminate artifacts such as beam-hardening and metallic artifacts. Virtual nonenhanced images have similar attenuation as true nonenhanced images and help in reducing radiation dose by eliminating the need for the latter in multiphasic vascular studies. Other potential applications of multienergy CT include calcium scoring from virtual nonenhanced images created from coronary CT angiograms and myocardial iron quantification. Online supplemental material is available for this article. RSNA, 2017.

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Acceptability of virtual unenhanced CT of the aorta as a replacement for the conventional unenhanced phase

Cited by 25 publications

References 15 publications

Reliability of virtual non-contrast computed tomography angiography: comparing it with the real deal

Reliability of virtual non-contrast computed tomography angiography: comparing it with the real deal

Alterations of immune response of non-small cell lung cancer with Azacytidine

Update on Cardiovascular Applications of Multienergy CT

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