We performed neural network clustering on dynamic contrast-enhanced perfusion magnetic resonance imaging time-series in patients with and without stroke. Minimal-free-energy vector quantization, ...self-organizing maps, and fuzzy c-means clustering enabled self-organized data-driven segmentation with respect to fine-grained differences of signal amplitude and dynamics, thus identifying asymmetries and local abnormalities of brain perfusion. We conclude that clustering is a useful extension to conventional perfusion parameter maps.
Abstract Objectives The aim of this study was to determine whether noncoronary measures from cardiac computed tomography (CT) may enhance the prognostic value of this imaging technology. Background ...When cardiac CT is performed for quantification of coronary artery calcium (CAC) score, information on other cardiac and thoracic structures is available. Methods Participants without known cardiovascular disease from the prospective population based Heinz Nixdorf Recall study underwent noncontrast cardiac CT for CAC score quantification. From CT, epicardial adipose tissue (EAT) volume, left ventricular and left atrial (LA) axial area index, ascending and descending aortic diameters, as well as aortic valve, mitral ring, and thoracic aortic calcification (TAC) were assessed. Incident cardiovascular events included myocardial infarction, stroke, and cardiovascular death. The prognostic value of CT-derived parameters was assessed by Cox regression analysis, receiver operating characteristics, and net reclassification improvement. Results From 3,630 subjects (59 ± 8 years of age, 46% male), 241 (6.6%) developed a cardiovascular event during 9.9 ± 2.6 years of follow-up. In multivariable Cox regression analysis including Framingham Risk Score, CAC (as logCAC + 1), and CT parameters, LA index (hazard ratio HR: 1.22 95% confidence interval CI: 1.05 to 1.41 per SD; p = 0.010) and EAT volume (HR: 1.15 95% CI: 1.01 to 1.30 per SD; p = 0.031) were significantly associated with incident events. In addition, presence of TAC showed an elevated event rate (HR: 1.33 95% CI: 0.97 to 1.81; p = 0.08), whereas all other CT-derived parameters showed no relevant association. The LA index, EAT volume, and presence of TAC together improved the prediction of events over Framingham Risk Score and CAC in receiver operating characteristics analysis (area under the curve: 0.749 to 0.764; p = 0.011), and let to a significant net reclassification improvement (HR: 38.0%; 95% CI: 25.1% to 50.8%). Conclusion Assessment of LA index, EAT volume, and TAC from non–contrast-enhanced cardiac CT improves the prediction of incident hard cardiovascular events above CAC and established risk factors, indicating that quantification of these noncoronary measures may improve the prognostic value of this imaging technology.
The primary aims of this retrospective study were to: (1) evaluate bone quality in different segments of the edentulous jaw and correlate it with demographic data and (2) establish a quantitative and ...objective assessment of bone quality based on the Hounsfield scale.
One hundred one randomly selected computerized tomographic (CT) scans were used for the analysis. Edentulous segments ranging from 10 to 30 mm were selected for evaluation, and the findings were analyzed and correlated to demographics. Implant recipient sites were evaluated visually for bone classification by 2 independent examiners. The same sites were subsequently evaluated digitally using the Hounsfield scale, and the results were correlated with the visual classification.
The 4 quadrants of the mouth displayed Hounsfield unit (HU) values ranging from -240 HU to 1,159 HU. The highest unit/mean density value (559 +/- 208 HU) was found in the anterior mandible, followed by 517 +/- 177 HU for the anterior maxilla, 333 +/- 199 HU for the posterior maxilla, and 321 +/- 132 HU for the posterior mandible. There was no association between the Hounsfield value and density and age or gender. When subjective bone quality was correlated to Hounsfield index findings, only the relationship between HU and type 4 bone was found to be significant.
Knowledge of the Hounsfield value as a quantitative measurement of bone density can be helpful as a diagnostic tool. It can provide the implant surgeon with an objective assessment of bone density, which could result in modification of surgical techniques or extended healing time, especially in situations where poor bone quality is suspected.
Aim To identify independent predictors of contrast medium-induced acute kidney injury (CI-AKI) after enhanced multidetector-row computed tomography (MDCT) prior to transcatheter aortic valve ...implantation (TAVI) in high-risk patients. Materials and methods The present single-centre study analysed retrospectively 361 patients who were assessed using MDCT prior to TAVI. CI-AKI was defined as an increase in serum creatinine (SCr) of ≥25% or ≥0.5 mg/dl in at least one sample over baseline (24 h before MDCT) and at 24, 48, and 72 h after MDCT. Results A total of 38 patients (10.5%) experienced CI-AKI. As compared to patients without CI-AKI, they presented more frequently with estimated glomerular filtration rate (eGFR) <60 ml/min/1.73m2 , (81.6% versus 64.4%, p = 0.045) and tended to receive higher volumes of iodinated contrast media (ICM; 55.3% versus 39%, p = 0.057). There was a significant interaction between baseline eGFR and the amount of intravenous ICM administered ( p for interaction = <0.001) identifying the amount of ICM >90 ml as independent predictive factor of CI-AKI only in patients with baseline eGFR <60 ml/min/1.73m2 (OR 2.615; 95% CI: 1.21–5.64). Conclusion One in ten elderly patients with aortic stenosis undergoing MDCT to plan a TAVI procedure experienced CI-AKI after intravenous ICM injection. Intravenous administration of <90 ml of ICM reduces this risk in patients with or without pre-existing impaired renal function. However, in the majority of patients renal function recovers before the TAVI procedure.
Changes in x-ray attenuating tissue caused by lung disorders like emphysema or fibrosis are subtle and thus only resolved by high-resolution computed tomography (CT). The structural reorganization, ...however, is of strong influence for lung function. Dark-field CT (DFCT), based on small-angle scattering of x-rays, reveals such structural changes even at resolutions coarser than the pulmonary network and thus provides access to their anatomical distribution. In this proof-of-concept study we present x-ray in vivo DFCTs of lungs of a healthy, an emphysematous and a fibrotic mouse. The tomographies show excellent depiction of the distribution of structural – and thus indirectly functional – changes in lung parenchyma, on single-modality slices in dark field as well as on multimodal fusion images. Therefore, we anticipate numerous applications of DFCT in diagnostic lung imaging. We introduce a scatter-based Hounsfield Unit (sHU) scale to facilitate comparability of scans. In this newly defined sHU scale, the pathophysiological changes by emphysema and fibrosis cause a shift towards lower numbers, compared to healthy lung tissue.
•We present so far unreported x-ray scatter dark-field CT scans of living mice performed with a Talbot–Lau interferometer.•Dark field gives access to structural information not provided by attenuation CT at scales below the detector pixel size.•Changes of lung alveoli structure are clearly visualized by dark-field CT for emphysema and fibrosis.
Lung diseases pose one of the leading causes of death worldwide. They are often difficult to diagnose at an early stage due to low sensitivity of conventional medical imaging systems towards structural changes of the lung tissue. With dark-field imaging based on scattering of x-rays such structural changes can be visualized even at imaging system resolutions coarser than the lung alveoli, as opposed to conventional x-ray imaging based on attenuation. By overcoming experimental scan time and dose issues, we report the first dark-field computed tomography scans on living mice, demonstrating excellent depiction of the anatomical distribution of pathological lung changes.
The aim of the study was to implement an abdominal CT angiography protocol using 100 kVp and to compare SNR and CNR, as well as subjective image quality, to a standard CT angiography protocol using ...120 kVp on a 16 detector-row CT scanner. Forty-eight patients were referred for routine abdominal CT angiography on a 16 detector-row CT scanner. Patients were scanned using either 120 or 100 kVp at constant mAs settings. Vessel opacification was provided by automated contrast injection using similar injection protocols. Density measurements were performed along the aorto-iliac axis with SNR and CNR calculation. In addition, the estimated effective patient radiation dose was calculated. Results of both protocols were compared. The 100-kVp protocol (432+/-80 HU) showed a significantly higher vessel density than the 120-kVp (333+/-90 HU; P<0.001) protocol, corresponding to an average increase in signal intensity of 30.7%. SNR (36.0 vs 37.0) and CNR (31.1 vs 31.7) for the 100-kV protocol were not significantly lower that those for the standard protocol (P=0.79 and P=0.87), whilst the average estimated dose was significantly lower using the 100-kVp protocol (6.7+/-0.4 vs 10.1+/-1.2 mSv; P<0.0001). Tube kVp reduction from 120 to 100 kVp allows for significant reduction of patient dose in abdominal CT angiography, without significant change in SNR,CNR and image quality.
The MRI study within the German National Cohort, a large-scale, population-based, longitudinal study in Germany, comprises comprehensive characterization and phenotyping of a total of 30 000 ...participants using 3-Tesla whole-body MR imaging. A multi-centric study design was established together with dedicated core facilities for e. g. managing incidental findings or providing quality assurance. As such, the study represents a unique opportunity to substantially impact imaging-based risk stratification leading to personalized and precision medicine. Supported by the developments in the field of computational science, the newly developing scientific field of radiomics has large potential for the future. In the present article we provide an overview on population-based imaging and Radiomics and conceptualize the rationale and design of the MRI study within the German National Cohort.
• Population-based imaging and Radiomics constitute two emerging fields with great oppertunities and challenges for Radiology.• As part of the MRI-study of the NAKO approximately 30 000 subjects will undergo 3 Tesla whole-body MRI.• MR Imaging data is publicly accessable and will provide important insights into the natural history of disease processes and personalized risk profiles of the general population. Citation Format: • Schlett CL, Hendel T, Weckbach S et al. Population-Based Imaging and Radiomics: Rationale and Perspective of the German National Cohort MRI Study. Fortschr Röntgenstr 2016; 188: 652 - 661.
The selection of patients for endovascular therapy is an important issue in stroke imaging. The aim of this study was to determine the predictive value of 3 different dynamic CT angiography ...parameters, occlusion length, collateralization extent, and time delay to maximum enhancement, for latest generation of stent retriever thrombectomy recanalization outcomes in patients with acute ischemic stroke.
In this study, subjects were selected from an initial cohort of 2059 consecutive patients who had undergone multiparametric CT, including whole-brain CT perfusion. We included all patients with a complete occlusion of the M1 segment of the MCA or the carotid T and subsequent intra-arterial stent retriever thrombectomy. Dynamic CT angiography was reconstructed from whole-brain CT perfusion raw datasets. Angiographic outcome was scored by using the modified TICI scale; and clinical outcome, by using the modified Rankin Scale. Logistic regression analyses were performed to determine independent predictors of a favorable angiographic (mTICI = 3) and clinical outcome (mRS ≤2).
Sixty-nine patients (mean age, 68 ± 14 years; 46% men) were included for statistical analysis. In the regression analysis, a short occlusion length was an independent predictor of favorable angiographic outcome (OR, 0.41; P < .05). Both collateralization grade (OR, 1.00; P > .05) and time delay to peak enhancement (OR, 0.90; P > .05) failed to predict a favorable angiographic outcome. None of the dynamic CT angiography predictors were significantly associated with clinical outcome on discharge (OR, 0.664-1.011; P = .330-.953) or at 90 days (OR, 0.779-1.016; P = .130-.845).
A short occlusion length as determined by dynamic CT angiography is an independent predictor of a favorable angiographic outcome of stent retriever thrombectomy in patients with ischemic stroke.
In clinically established-absorption-based-biomedical x-ray imaging, contrast agents with high atomic numbers (e.g. iodine) are commonly used for contrast enhancement. The development of novel x-ray ...contrast modalities such as phase contrast and dark-field contrast opens up the possible use of alternative contrast media in x-ray imaging. We investigate using ultrasound contrast agents, which unlike iodine-based contrast agents can also be administered to patients with renal impairment and thyroid dysfunction, for application with a recently developed novel x-ray dark-field imaging modality. To produce contrast from these microbubble-based contrast agents, our method exploits ultra-small-angle coherent x-ray scattering. Such scattering dark-field x-ray images can be obtained with a grating-based x-ray imaging setup, together with refraction-based differential phase-contrast and the conventional attenuation contrast images. In this work we specifically show that ultrasound contrast agents based on microbubbles can be used to produce strongly enhanced dark-field contrast, with superior contrast-to-noise ratio compared to the attenuation signal. We also demonstrate that this method works well with an x-ray tube-based setup and that the relative contrast gain even increases when the pixel size is increased from tenths of microns to clinically compatible detector resolutions about up to a millimetre.
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