Diagnostic accuracy of a noninvasive hepatic ultrasound score for non-alcoholic fatty liver disease (NAFLD) in the Brazilian Longitudinal Study of Adult Health (ELSA-Brasil)

CONTEXT AND OBJECTIVE: Noninvasive strategies for evaluating non-alcoholic fatty liver disease (NAFLD) have been investigated over the last few decades. Our aim was to evaluate the diagnostic accuracy of a new hepatic ultrasound score for NAFLD in the ELSA-Brasil study.DESIGN AND SETTINGS: Diagnostic accuracy study conducted in the ELSA center, in the hospital of a public university.METHODS: Among the 15,105 participants of the ELSA study who were evaluated for NAFLD, 195 individuals were included in this sub-study. Hepatic ultrasound was performed (deep beam attenuation, hepatorenal index and anteroposterior diameter of the right hepatic lobe) and compared with the hepatic steatosis findings from 64-channel high-resolution computed tomography (CT). We also evaluated two clinical indices relating to NAFLD: the fatty liver index (FLI) and the hepatic steatosis index (HSI).RESULTS: Among the 195 participants, the NAFLD frequency was 34.4%. High body mass index, high waist circumference, diabetes and hypertriglyceridemia were associated with high hepatic attenuation and large anteroposterior diameter of the right hepatic lobe, but not with the hepatorenal index. The hepatic ultrasound score, based on hepatic attenuation and the anteroposterior diameter of the right hepatic lobe, presented the best performance for NAFLD screening at the cutoff point ≥ 1 point; sensitivity: 85.1%; specificity: 73.4%; accuracy: 79.3%; and area under the curve (AUC 0.85; 95% confidence interval, CI: 0.78-0.91)]. FLI and HSI presented lower performance (AUC 0.76; 95% CI: 0.69-0.83) than CT.CONCLUSION: The hepatic ultrasound score based on hepatic attenuation and the anteroposterior diameter of the right hepatic lobe has good reproducibility and accuracy for NAFLD screening

Multimodality Assessment of the Vascular Complications of Adult Liver Transplantation

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A structural-functional MRI-based disease atlas: application to computer-aided-diagnosis of prostate cancer

ABSTRACT Different imaging modalities or protocols of a single patient may convey different types of information regarding a disease for the same anatomical organ/tissue. On the other hand, multi-modal/multi-protocol medical images from several different patients can also provide spatial statistics of the disease occurrence, which in turn can greatly aid in disease diagnosis and aid in improved, accurate biopsy and targeted treatment. It is therefore important to not only integrate medical images from multiple patients into a common coordinate frame (in the form of a population-based atlas), but also find the correlation between these multi-modal/multi-protocol data features and the disease spatial distribution in order to identify different quantitative structural and functional disease signatures. Most previous work on construction of anatomical atlases has focused on deriving a population-based atlas for the purpose of deriving the spatial statistics. Moreover, these models are typically derived from normal or healthy subjects, either explicitly or implicitly, where it is assumed that the inter-patient pathological variation is not large. These methods are not suitable for constructing a disease atlas, where significant differences between patients on account of disease related variations can be expected. In this paper, we present a novel framework for the construction of a multi-parametric MRI-based data-driven disease atlas consisting of multi-modal and multi-protocol data from across multiple patient studies. Our disease atlas contains 3 Tesla structural (T2) and functional (dynamic contrast enhanced (DCE)) prostate in vivo MRI with corresponding whole mount histology specimens obtained via radical prostatectomy. Our atlas construction framework comprises 3 distinct modules: (a) determination of disease spatial extent on the multi-protocol MR imagery for each patient, (b) construction of a multi-protocol MR imaging spatial atlas which captures the geographical proclivity of the disease, and (c) feature extraction and the construction of the data-driven multi-protocol MRI based prostate cancer atlas. The marriage of data driven and spatial atlases could serve as a useful tool for clinicians to identifying structural and functional imaging disease signatures so as to make better, more informed diagnoses. Each spatial location in this atlas can be associated with a high dimensional multi-attribute quantitative feature vector. Additionally, since the feature vectors are extracted from across multiple patient studies, each spatial location in the data-driven atlas can be characterized by a feature distribution (in turn characterized by a mean and standard deviation). Preliminary investigation in quantitatively correlating the disease signatures from across the spatial and data driven atlases suggests that our quantitative atlas framework could emerge as a powerful tool for discovering prostate cancer imaging signatures

Peripheral vascular disease evaluated with reduced-dose gadolinium-enhanced MR angiography

PURPOSE: To demonstrate the utility of low-dose gadolinium-enhanced magnetic resonance (MR) angiography of two consecutive anatomic areas for assessment of peripheral vascular disease. MATERIALS AND METHODS: Fifteen patients underwent gadolinium-enhanced MR angiography for evaluation of lower extremity peripheral vascular disease after conventional digital subtraction angiography (DSA). MR angiography was performed with three-dimensional coronal gradient-echo acquisitions before and during administration of gadopentetate dimeglumine. Two separate, contiguous areas were studied with separate doses of 0.075 and 0.1 mmol/kg gadopentetate dimeglumine. MR angiography findings were compared with DSA findings; DSA was the standard of reference. Treatment options were determined first with MR angiograms and then with DSA images. RESULTS: For distinguishing greater than 50% stenosis from 50% or less stenosis, gadolinium-enhanced MR angiography yielded a sensitivity of 97%, a specificity of 96%, and an accuracy of 97%. In 146 (97%) of 150 anatomic segments, there was essential or total agreement on treatments determined with MR angiography and DSA. In two cases (one case of vascular stent placement and one case of surgical anastomosis), extent of disease was overestimated with MR angiography. The MR study of one infrapopliteal area was insufficient for evaluation. CONCLUSION: Accurate gadolinium-enhanced MR angiography of multiple peripheral vascular areas of the lower extremities can be performed in most patients with less than 0.2 mmol/kg contrast material

Suppression of venous signal in time-of-flight MR angiography of the lower extremities after administration of gadopentetate dimeglumine

PURPOSE: To evaluate a magnetic resonance (MR) angiography time-of-flight technique that can effectively suppress venous signal after gadopentetate dimeglumine administration. MATERIALS AND METHODS: Twelve adult patients underwent MR angiography for the evaluation of peripheral vascular disease. Gradient-echo sequences were performed after the administration of 0.2 mmol/kg gadopentetate dimeglumine. Three sequences were compared: a nontriggered sequence; a gap sequence, an electrocardiographically triggered, segmented sequence with a 7-mm gap between saturation and imaging sections; and a no-gap sequence, a similar sequence as gap but with partially overlapping imaging and saturation sections. For each sequence, identical regions of interest were generated for arterial, venous, and background muscle tissue and noise. A paired Student t test was used to compare the signal-to-noise and contrast-to-noise ratios (C/Ns) among the sequences. In seven patients, the no-gap sequence was used to acquire MR angiograms of the distal lower extremities. RESULTS: The mean artery-muscle C/N was similar for the triggered sequences; both were statistically significantly greater than the ratios for the nontriggered sequence. Venous suppression was much better with the no-gap sequence. Overall, the best artery-vein C/N was also obtained with the no-gap sequence. MR angiograms with effective venous suppression could be obtained only with the no-gap sequence. CONCLUSION: Time-of-flight MR angiograms can be obtained with effective venous suppression after the administration of 0.2 mmol/kg gadopentetate dimeglumine