Dual-layer detector CT of the head: Initial experience in visualization of intracranial hemorrhage and hypodense brain lesions using virtual monoenergetic images

Lennartz, Simon; Laukamp, Kai Roman; Neuhaus, Victor; Hokamp, Nils Große; Blanc, Markus Le; Maus, Volker; Kabbasch, Christoph; Mpotsaris, Anastasios; Maintz, David; Borggrefe, Jan

doi:10.1016/j.ejrad.2018.09.010

Cited by 31 publications

(37 citation statements)

References 22 publications

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“…While different emission-based DECT systems have been available for more than a decade, recently, a detector-based approach was introduced, referred to as spectral detector CT (SDCT). By using a dual-layer detector, it enables a simultaneous detection of low-and high-energy photons with complete temporal and spatial registration, allowing for a retrospective reconstruction of VMIs in a range from 40 to 200 kiloelectronvolt (keV) for every scan [10][11][12].…”

Section: Introductionmentioning

confidence: 99%

Virtual monoenergetic images from spectral detector computed tomography facilitate washout assessment in arterially hyper-enhancing liver lesions

et al. 2020

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Objectives To investigate whether the increased soft tissue contrast of virtual monoenergetic images (VMIs) obtained from a spectral detector computed tomography (SDCT) system improves washout assessment of arterially hyper-enhancing liver lesions. Methods Fifty-nine arterially hyper-enhancing lesions in 31 patients (age 65 ± 9 years, M/W 20/11) were included in this IRB-approved study. All patients underwent multi-phase SDCT for HCC screening. MRI, CEUS or biopsy within 3 months served as standard of reference to classify lesions as LiRADS 3 or 4/5. VMIs and conventional images (CIs) were reconstructed. Visual analysis was performed on 40, 60, and 80 kiloelectronvolt (keV) and CIs by 3 radiologists. Presence and visibility of washout were assessed; image quality and confidence of washout evaluation were evaluated on 5-point Likert scales. Signal-to-noise ratio (SNR), lesion-to-liver contrast-to-noise ratio (CNR) (|HUlesion–HUliver|/SDliver) and washout (|HUlesion–HUliver|) were calculated. Statistical assessment was performed using ANOVA and Wilcoxon test. Results On subjective lesion analysis, the highest level of diagnostic confidence and highest sensitivity for the detection of lesion washout were found for 40-keV VMIs (40 keV vs. CI, 81.3 vs. 71.3%). Image quality parameters were significantly better in low-kiloelectronvolt VMIs than in CIs (p < 0.05; e.g. SNRliver: 40 keV vs. CIs, 12.5 ± 4.1 vs. 5.6 ± 1.6). In LiRADS 4/5 lesions, CNR and quantitative washout values were significantly higher in 40-keV VMIs compared to CIs (p < 0.05; e.g. CNR and washout in 40 keV vs. CIs, 2.3 ± 1.6 vs. 0.8 ± 0.5 and 29.0 ± 19.1 vs. 12.9 ± 6.9 HU, respectively). Conclusion By increasing lesion contrast, low-kiloelectronvolt VMIs obtained from SDCT improve washout assessment of hyper-enhancing liver lesions with respect to washout visibility and diagnostic confidence. Key Points • Low-kiloelectronvolt virtual monoenergetic images from spectral detector CT facilitate washout assessment in arterially hyper-enhancing liver lesions. • Image quality and quantitative washout parameters as well as subjective washout visibility and diagnostic confidence benefit from low-kiloelectronvolt virtual monoenergetic images.

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Section: Introductionmentioning

confidence: 99%

Virtual monoenergetic images from spectral detector computed tomography facilitate washout assessment in arterially hyper-enhancing liver lesions

et al. 2020

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“…Mean optimal keV values for diagnostic assessment were significantly lower in combination of VMI with MAR (~170 keV) compared to VMI (~180 keV) alone. Due to their physical properties higher keV VMI reduce brain tissue contrast 26,29 , the combination of VMI and MAR enables to receive optimal artifact reduction at lower keV values, where loss of tissue contrast is lower 14,22,26,29 . To achieve optimal results, we therefore recommend using the combination VMI and MAR between 140 to 200 keV.…”

Section: Discussionmentioning

confidence: 99%

Virtual monoenergetic images and post-processing algorithms effectively reduce CT artifacts from intracranial aneurysm treatment

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et al. 2020

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To evaluate artifact reduction by virtual monoenergetic images (VMI) and metal artifact reduction algorithms (MAR) as well as the combination of both approaches (VMI MAR) compared to conventional CT images (CI) as standard of reference. In this retrospective study, 35 patients were included who underwent spectral-detector CT (SDCT) with additional MAR-reconstructions due to artifacts from coils or clips. CI, VMI, MAR and VMI MAR (range: 100-200 keV, 10 keV-increment) were reconstructed. Region-of-interest based objective analysis was performed by assessing mean and standard deviation of attenuation (HU) in hypo-and hyperdense artifacts from coils and clips. Visually, extent of artifact reduction and diagnostic assessment were rated. Compared to CI, VMI ≥ 100 keV, MAR and VMI MAR between 100-200 keV increased attenuation in hypoattenuating artifacts (CI/VMI 200keV /MAR/VMI MAR200keV , HU: −77.6 ± 81.1/−65.1 ± 103.2/−36.9 ± 27.7/−21.1 ± 26.7) and decreased attenuation in hyperattenuating artifacts (HU: 47.4 ± 32.3/42.1 ± 50.2/29.5 ± 18.9/20.8 ± 25.8). However, differences were only significant for MAR in hypodense and VMI MAR in hypo-and hyperdense artifacts (p < 0.05). Visually, hypo-and hyperdense artifacts were significantly reduced compared to CI by VMI ≥140/100keV , MAR and VMI MAR≥100keV. Diagnostic assessment of surrounding brain tissue was significantly improved in VMI ≥100keV , MAR and VMI MAR≥100keV. The combination of VMI and MAR facilitates a significant reduction of artifacts adjacent to intracranial coils and clips. Hence, if available, these techniques should be combined for optimal reduction of artifacts following intracranial aneurysm treatment. Intracranial aneurysms are a common vascular disorder with a prevalence of approximately 4%, which can be expected to increase due to an ageing population 1,2. In case of rupture they are associated with a mortality risk of up to 50% [1]. Ruptured as well as unruptured aneurysms are commonly treated with surgical clipping or endovascular coiling 3,4. Postoperative imaging is pivotal to detect postoperative complications and ensure therapy success for which computed tomography (CT) is frequently applied besides digital subtraction angiography and magnetic resonance imaging 5. However, evaluation of brain parenchyma adjacent to clips and coils is often impaired by metal artifacts. Artifacts commonly appear as hypo-and hyperdense areas surrounding the metal material. These kind of artifacts result from a combination of beam-hardening caused by absorption of low energetic photons 6,7 , photon starvation resulting from complete absorption of all photons 7,8 , and scatter artifacts that can occur due to greater attenuation differences, e.g. soft tissue and dense metal material 9. Combined, these effects can result in strong interferences that may impair depiction and interpretation of surrounding brain tissue. Therefore, evaluation of post-interventional complications, such as tissue damage, haemorrhage, infarction and oedema may be limited 10. Further, any futur...

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“…Dual-layer spectral CT (DLCT) acquisitions allow material decomposition (virtual non-contrast, iodine-only imaging, and effective atomic numbers) as well as the calculation of virtual monoenergetic images. Several clinical studies have already been performed showing the advantages of DLCT for head CT for imaging intracerebral lesions and hemorrhage, for thoracic CT, for vertebral CT for differentiating bone lesions, and for abdominal CT angiographies for improved delineation of visceral arteries [ 1 – 5 ]. However, for the image acquisition of such data, a tube potential of either 140 kVp or 120 kVp is necessary to allow for spectral decomposition under the exploitation of the energy-specific x-ray absorption of different materials.…”

Section: Introductionmentioning

confidence: 99%

Image quality evaluation of dual-layer spectral CT in comparison to single-layer CT in a reduced-dose setting

et al. 2020

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Objectives To quantitatively and qualitatively evaluate image quality in dual-layer CT (DLCT) compared to single-layer CT (SLCT) in the thorax, abdomen, and pelvis in a reduced-dose setting. Methods Intraindividual, retrospective comparisons were performed in 25 patients who received at least one acquisition of all three acquisition protocols SLCTlow (100 kVp), DLCThigh (120 kVp), and DLCTlow (120 kVp), all covering the venous-phase thorax, abdomen, and pelvis with matched CTDIvol between SLCTlow and DLCTlow. Reconstruction parameters were identical between all scans. Image quality was assessed quantitatively at 10 measurement locations in the thorax, abdomen, and pelvis by two independent observers, and subjectively with an intraindividual forced choice test between the three acquisitions. Dose-length product (DLP) and CTDIvol were extracted for dose comparison. Results Despite matched CTDIvol in acquisition protocols, CTDIvol and DLP were lower for SLCTlow compared to DLCTlow and DLCThigh (DLP 408.58, 444.68, 647.08 mGy·cm, respectively; p < 0.0004), as automated tube current modulation for DLCTlow reached the lower limit in the thorax (mean 66.1 mAs vs limit 65 mAs). Noise and CNR were comparable between SLCTlow and DLCTlow (p values, 0.29–0.51 and 0.05–0.20), but CT numbers were significantly higher for organs and vessels in the upper abdomen for SLCTlow compared to DLCTlow. DLCThigh had significantly better image quality (Noise and CNR). Subjective image quality was superior for DLCThigh, but no difference was found between SLCTlow and DLCTlow. Conclusions DLCTlow showed comparable image quality to SLCTlow, with the additional possibility of spectral post-processing. Further dose reduction seems possible by decreasing the lower limit of the tube current for the thorax. Key Points • Clinical use of reduced-dose DLCT is feasible despite the required higher tube potential. • DLCT with reduced dose shows comparable objective and subjective image quality to reduced-dose SLCT. • Further dose reduction in the thorax might be possible by adjusting mAs thresholds.

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Dual-layer detector CT of the head: Initial experience in visualization of intracranial hemorrhage and hypodense brain lesions using virtual monoenergetic images

Cited by 31 publications

References 22 publications

Virtual monoenergetic images from spectral detector computed tomography facilitate washout assessment in arterially hyper-enhancing liver lesions

Virtual monoenergetic images from spectral detector computed tomography facilitate washout assessment in arterially hyper-enhancing liver lesions

Virtual monoenergetic images and post-processing algorithms effectively reduce CT artifacts from intracranial aneurysm treatment

Image quality evaluation of dual-layer spectral CT in comparison to single-layer CT in a reduced-dose setting

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