To compare and combine dual-energy based and iterative metal artefact reduction on hip prosthesis and dental implants in CT.
A total of 46 patients (women:50%,mean age:63±15years) with dental ...implants or hip prostheses (n = 30/20) were included and examined with a second-generation Dual Source Scanner. 120kV equivalent mixed-images were derived from reconstructions of the 100/Sn140kV source images using no metal artefact reduction (NOMAR) and iterative metal artefact reduction (IMAR). We then generated monoenergetic extrapolations at 130keV from source images without IMAR (DEMAR) or from source images with IMAR, (IMAR+DEMAR). The degree of metal artefact was quantified for NOMAR, IMAR, DEMAR and IMAR+DEMAR using a Fourier-based method and subjectively rated on a five point Likert scale by two independent readers.
In subjects with hip prosthesis, DEMAR and IMAR resulted in significantly reduced artefacts compared to standard reconstructions (33% vs. 56%; for DEMAR and IMAR; respectively, p<0.005), but the degree of artefact reduction was significantly higher for IMAR (all p<0.005). In contrast, in subjects with dental implants only IMAR showed a significant reduction of artefacts whereas DEMAR did not (71%, vs. 8% p<0.01 and p = 0.1; respectively). Furthermore, the combination of IMAR with DEMAR resulted in additionally reduced artefacts (Hip prosthesis: 47%, dental implants 18%; both p<0.0001).
IMAR allows for significantly higher reduction of metal artefacts caused by hip prostheses and dental implants, compared to a dual energy based method. The combination of DE-source images with IMAR and subsequent monoenergetic extrapolation provides an incremental benefit compared to both single methods.
Aims/hypothesis
Obesity-linked ectopic fat accumulation is associated with the development of type 2 diabetes. Whether pancreatic and liver steatosis impairs insulin secretion is controversial. We ...examined the crosstalk of human pancreatic fat cells with islets and the role of diabetogenic factors, i.e. palmitate and fetuin-A, a hepatokine released from fatty liver.
Methods
Human pancreatic resections were immunohistochemically stained for insulin, glucagon, somatostatin and the macrophage/monocyte marker CD68. Pancreatic adipocytes were identified by Oil Red O and adiponectin staining. Primary pancreatic pre-adipocytes and differentiated adipocytes were co-cultured with human islets isolated from organ donors and the metabolic crosstalk between fatty liver and fatty pancreas was mimicked by the addition of palmitate and fetuin-A. Insulin secretion was evaluated by ELISA and RIA. Cytokine expression and secretion were assessed by RT-PCR and multiplex assay, respectively. Subcellular distribution of proteins was examined by confocal microscopy and protein phosphorylation by western blotting.
Results
In human pancreatic parenchyma, highly differentiated adipocytes were detected in the proximity of islets with normal architecture and hormone distribution. Infiltration of adipocytes was associated with an increased number of CD68-positive cells within islets. In isolated primary pancreatic pre-adipocytes and differentiated adipocytes, palmitate and fetuin-A induced
IL6
,
CXCL8
and
CCL2
mRNA expression. Cytokine production was toll-like receptor 4 (TLR4)-dependent and further accentuated in pre-adipocytes when co-cultured with islets. In islets,
IL6
and
CXCL8
mRNA levels were also increased by fetuin-A and palmitate. Only in macrophages within the isolated islets, palmitate and fetuin-A stimulated the production of the cytotoxic cytokine IL-1β. Palmitate, but not fetuin-A, exerted pro-apoptotic effects in islet cells. Instead, fetuin-A impaired glucose-induced insulin secretion in a TLR4-independent, but c-Jun N-terminal kinase- and Ca
2+
-dependent, manner.
Conclusions/interpretation
These results provide the first evidence that fetuin-A-mediated metabolic crosstalk of fatty liver with islets may contribute to obesity-linked glucose blindness of beta cells, while fatty pancreas may exacerbate local inflammation.
Ischemic brain edema is subtle and hard to detect by computed tomography within the first hours of stroke onset. We hypothesize that non-enhanced CT (NECT) post-processing with frequency-selective ...non-linear blending ("best contrast"/BC) increases its accuracy in detecting edema and irreversible tissue damage (infarction).
We retrospectively analyzed the NECT scans of 76 consecutive patients with ischemic stroke (exclusively middle cerebral artery territory-MCA) before and after post-processing with BC both at baseline before reperfusion therapy and at follow-up (5.73±12.74 days after stroke onset) using the Alberta Stroke Program Early CT Score (ASPECTS). We assessed the differences in ASPECTS between unprocessed and post-processed images and calculated sensitivity, specificity, and predictive values of baseline NECT using follow-up CT serving as reference standard for brain infarction.
NECT detected brain tissue hypoattenuation in 35 of 76 patients (46.1%). This number increased to 71 patients (93.4%) after post-processing with BC. Follow-up NECT confirmed brain infarctions in 65 patients (85.5%; p = 0.012). Post-processing increased the sensitivity of NECT for brain infarction from 35/65 (54%) to 65/65 (100%), decreased its specificity from 11/11 (100%) to 7/11 (64%), its positive predictive value (PPV) from 35/35 (100%) to 65/69 (94%) and increased its accuracy 46/76 (61%) to 72/76 (95%).
This post-hoc analysis suggests that post-processing of NECT with BC may increase its sensitivity for ischemic brain damage significantly.
Abstract
OBJECTIVES
Preventing type A aortic dissection requires reliable prediction. We developed and validated a multivariable prediction model based on anthropometry to define patient-adjusted ...thresholds for aortic diameter and length.
METHODS
We analysed computed tomography angiographies and clinical data from 510 control patients, 143 subjects for model validation, 125 individuals with ascending aorta ectasia (45–54 mm), 58 patients with aneurysm (≥55 mm), 206 patients with type A aortic dissection and 19 patients who had received a computed tomography angiography ≤2 years before they suffered from a type A aortic dissection. Computed tomography angiographies were analysed using curved planar reformations.
RESULTS
In the control group, the mean ascending aortic diameter was 33.8 mm standard deviation (SD) ±5.2 mm, and the length, measured from the aortic valve to the brachiocephalic trunk, was 91.9 mm (SD ±12.2 mm); both diameter and length were correlated with anthropometric parameters and were smaller than the respective values in all pathological groups (P < 0.001). Multivariable linear regression analysis of the control group revealed that age, sex and body surface area were predictors of ascending aorta diameter (R2 = 0.40) and length (R2 = 0.26). Bicuspidity of the aortic valve was not included in the model; its prevalence was only 3.2% in the control group but >25% in the ectasia and aneurysm groups.
CONCLUSIONS
The regression model provides a patient-adjusted prediction of the thresholds for aortic diameter and length. In our retrospective data, the model resulted in better identification of aortas at the risk of dissection than the conventional 55-mm diameter threshold. The model is available as an Internet calculator (www.aorticcalculator.com).
•No significant difference in muscular fat quantification between DECT and MRI.•Systematic underestimation of −1.7% of liver fat in DECT compared to MRI.•Liver and muscular fat quantification in ...portal-venous phase DECT is feasible.
To investigate the feasibility of liver fat quantification in contrast-enhanced dual source dual energy computed tomography (DECT) using multi-echo Dixon magnetic resonance imaging (MRI) as reference standard.
Patients who underwent MRI of the liver including a multi-echo Dixon sequence for estimation of proton density fat fraction in 2017 as well as contrast-enhanced DECT imaging of the abdomen were included in this retrospective, monocentric IRB approved study. Furthermore, patients with a hepatic fat amount >5% who were examined in 2018 with MRI and DECT were included. The final study group consisted of 81 patients with 90 pairs of examinations. Analysis of parameter maps was performed manually using congruent regions of interest which were placed in the liver parenchyma, in the erector spinae muscles, and psoas major muscles.
Mean patient age was 61 ± 13 years. Median time between MRI and DECT was 48 days. MRI liver fat quantification resulted in a median of 3.8% (IQR: 2.2–8.2%) compared to 1.8% (IQR: 0–6.3%) in DECT (p < 0.001), with a Spearman correlation of 0.73. Bland-Altman analysis resulted in a systematic underestimation of liver fat in DECT, with a mean difference of −1.7%. Fat quantification in the erector spinae muscles (p = 0.257) and the psoas major muscles (p = 0.208) was not significantly different in DECT compared to MRI.
Liver and muscular fat quantification in portal-venous phase DECT is feasible with good to excellent correlation compared to a multi-echo Dixon MRI sequence analysis. While there is an underestimation of the liver fat content in DECT, there are no significant differences between DECT and MRI fat quantification of the erector spinae and psoas major muscles.
PURPOSE The purpose of this study is to systematically evaluate the effect of tube voltage, current kernels, and monoenergetic post-processing on stent visualization. METHODS A 6 mm chrome-cobalt ...peripheral stent was placed in a dedicated phantom and scanned with the available tube voltage settings of a third-generation dual-source scanner in single-energy (SE) and dual-energy (DE) mode. Images were reconstructed using the latest convolution kernels and monoenergetic reconstructions (40-190 keV) for DE. The sharpness of stent struts (S), struts width (SW), contr ast-t o-noi se-ra tios (CNR), and pseudoenhancement (PE) between the vessel with and without stent were analyzed using an in-house built automatic analysis tool. Measurements were standardized through calculated z-scores. Z-scores were combined for stent (SQ), luminal (LQ), and overall depiction quality (OQ) by adding S and SW, CNR and SW and PE, and S and SW and CNR and PE. Two readers rated overall stent depiction on a 5-point Likert-scale. Agreement was calculated using linear-weighted kappa. Correlations were calculated using Spearman correlation coefficient. RESULTS Maximum values of S and CNR were 169.1 HU/pixel for DE; 100/ Sn 150 kV; Qr59; 40 keV and 50.0 for SE; 70 kV; Bv36. Minimum values of SW and PE were 2.615 mm for DE; 80 to 90/ Sn 150 kV; Qr59; 140 to 190 keV and 0.12 HU for DE; 80/ Sn 150 kV; Qr36; 190 keV. Best combined z-scores of SQ, LQ, and OQ were 4.53 for DE; 100/ Sn 150 kV; Qr 59; 40 keV, 1.23 for DE; 100/ Sn 150 kV; Qr59; 140 keV and 2.95 for DE; 90/ Sn 150 kV; Qr59; 50 keV. Best OQ of SE was ranked third with 2.89 for SE; 90 kV; Bv59. Subjective agreement was excellent (kappa = 0.86; P < .001) and correlated well with OQ (r.sub.s = 0.94, P < .001). CONCLUSION Combining DE computed tomography (CT) acquisition with the latest kernels and monoenergetic post-processing allows for improved stent visualization as compared with SECT. The best overall results were obtained for monoenergetic reconstructions with 50 keV from DECT 90/Sn 150 kV acquisitions using kernel Qr59.
To assess virtual non-enhanced dual energy computed tomography (DECT) reconstruction as a potential alternative to true non-enhanced thoracic and abdominal CT scans in patients with suspected active ...hemorrhage.
Ninety-seven consecutive patients with suspected active bleeding, who underwent routine triphasic CT with intravenous contrast, were included. All patients underwent single energy non-enhanced (TNE) and arterial phase CT as well as venous DECT. Using commercially available software, venous dual energy images were used to generate virtual non-enhanced images (VNE). TNE and VNE were evaluated regarding subjective image quality and diagnostic confidence on a 5-point-scale. The consistency of interpretation with respect to presence and type of hemorrhage between conventional triphasic CT including TNE and biphasic CT with simulated VNE was assessed by two blinded independent readers.
Among the included subjects (mean age: 66.3 ± 14.5 years, 63.9% male), 37.1% were diagnosed with acute hemorrhage. VNE yielded significantly lower image quality but superior reduction of artefacts as compared to TNE (p ≤ 0.001). Diagnostic confidence was rated high for both TNE and VNE with a significant superiority of TNE (p = 0.003). Triphasic and biphasic CT datasets yielded perfect intrareader agreement regarding presence and type of hemorrhage. The interrater agreement was almost perfect (K = 0.955). Radiation dose was significantly reduced using biphasic dual energy CT with VNE (p ≤ 0.001).
Virtual non-enhanced images yield comparable diagnostic confidence and perfect agreement with true non-enhanced images for assessment of acute hemorrhage. This suggests that true non-enhanced images could be replaced by virtual non-enhanced images resulting in a significant reduction of radiation dose.
Background and Purpose
To compare the accuracy of subjective Alberta Stroke Program Early CT Score (sASPECTS) evaluation and that of an automated prototype software (aASPECTS) on nonenhanced CT ...(NECT) in patients with early anterior territory stroke and controls using side‐to‐side quantification of hypoattenuated brain areas.
Methods
We retrospectively analyzed the NECT scans of 42 consecutive patients with ischemic stroke before reperfusion and 42 controls using first sASPECTS and subsequently aASPECTS. We assessed the differences in Alberta Stroke Program Early CT Score (ASPECTS) and calculated the sensitivity and specificity of NECT with CT perfusion, whereas cerebral blood volume (CBV) served as the reference standard for brain infarction.
Results
The clot was located in the middle cerebral artery (MCA) in 47.6% of cases and the internal carotid artery (ICA) in 28.6% of cases. Ten cases presented combined ICA and MCA occlusions. The stroke was right sided in 52.4% of cases and left sided in 47.6%. Reader‐based NECT analysis yielded a median sASPECTS of 10. The median CBV‐based ASPECTS was 7. Compared to the area of decreased CBV, sASPECTS yielded a sensitivity of 12.5% and specificity of 86.8%. The software prototype (aASPECTS) yielded an overall sensitivity of 65.5% and a specificity of 92.2%. The interreader agreement for ASPECTS evaluation of admission NECT and follow‐up CT was almost perfect (κ = .93). The interreader agreement of the CBV color map evaluation was substantial (κ = .77).
Conclusions
aASPECTS of NECT can outperform sASPECTS for stroke detection.
PURPOSE Differentiation of incidental adrenal lesions remains a challenge in diagnostic imaging, especially on single-phase portal venous computed tomography (CT) in the oncological setting. The aim ...of the study was to explore the ability of dual-energy CT (DECT)-based iodine quantification and virtual non-contrast (VNC) imaging and advanced radiomic analysis of DECT for differentiation of adrenal adenomas from metastases. METHODS A total of 46 patients with 49 adrenal lesions underwent clinically indicated staging DECT and magnetic resonance imaging. Median values of quantitative parameters such as VNC, fat fraction, and iodine density in DECT images were collected and compared between adenomas and metastases using non-parametric tests. Magnetic resonance imaging, washout CT, and clinical follow-up were used as a reference standard. Diagnostic accuracy was assessed by calculating receiver operating characteristics. A DECT tumor analysis prototype software was used for semiautomatic segmentation of adrenal lesions and extraction of radiomic features. A radiomics prototype was used to analyze the data with multiple logistic regression and random forest classification to determine the area under the curve (AUC). RESULTS The study cohort (60.87% women; mean age: 66.91 + or - 12.93 years) consisted of 32 adenomas and 17 metastases. DECT-based VNC imaging (AUC = 0.89) and fat quantification (AUC = 0.86) differentiate between adrenal adenomas and metastases with high diagnostic accuracy (P < .001). Analysis of radiomic features revealed that DECT features such as VNC imaging and fat fraction (AUC = 0.87-0.89; < .001) and radiomic features such as 90th percentile and total energy (AUC = 0.88-0.93; P < .001) differentiate with high diagnostic accuracy between adrenal adenomas and metastases. Random forest classification revealed an AUC of 0.83 for separating adrenal adenomas from metastases. CONCLUSION Virtual non-contrast imaging and fat quantification as well as extraction of radiomic features accurately differentiate between adrenal adenomas and metastases on single-phase oncologic staging DECT.
This study investigated the efficacy of single-phase dual-energy CT (DECT) in differentiating pulmonary hamartomas from malignant lung lesions using virtual non-contrast (VNC), iodine, and fat ...quantification. Forty-six patients with 47 pulmonary lesions (mean age: 65.2 ± 12.1 years; hamartomas-to-malignant lesions = 22:25; male: 67%) underwent portal venous DECT using histology, PET-CT and follow-up CTs as a reference. Quantitative parameters such as VNC, fat fraction, iodine density and CT mixed values were statistically analyzed. Significant differences were found in fat fractions (hamartomas: 48.9%; malignancies: 22.9%;
≤ 0.0001) and VNC HU values (hamartomas: -20.5 HU; malignancies: 17.8 HU;
≤ 0.0001), with hamartomas having higher fat content and lower VNC HU values than malignancies. CT mixed values also differed significantly (
≤ 0.0001), but iodine density showed no significant differences. ROC analysis favored the fat fraction (AUC = 96.4%; sensitivity: 100%) over the VNC, CT mixed value and iodine density for differentiation. The study concludes that the DECT-based fat fraction is superior to the single-energy CT in differentiating between incidental pulmonary hamartomas and malignant lesions, while post-contrast iodine density is ineffective for differentiation.
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