Navegando por Palavras-chave "Elastography"
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- ItemSomente MetadadadosAnálise de metodologias de pixel tracking dedicadas para a caracterização das lesões ateroscleróticas 2d em estruturas coronárias através de phantoms computacionais(Universidade Federal de São Paulo (UNIFESP), 2019-09-13) Grinet, Marco Antonio Vieira Macedo [UNIFESP]; Moraes, Matheus Cardoso [UNIFESP]; Universidade Federal de São Paulo (UNIFESP)Atherosclerosis is a cardiovascular disease of the arterial wall that occurs in susceptible areas of the main arteries and accumulates an estimated cost of over US$186 billion worldwide. Atherosclerotic lesions are caused by the retention of lipids and form plaques in the internal arterial wall. The risk factor of the patient with atherosclerosis is proportional to morphological aspects and composition of the plaque. Intravascular Ultrasound (IVUS) is a medical imaging modality widely used for evaluating atherosclerotic plaques through elastography. To properly perform elastography, it is necessary to track the displacement of the atherosclerotic plaques by using speckle tracking methods. However, many of the current speckle tracking methods present in the literature were developed for general ultrasound imaging applications, and there no specific method designed for IVUS imaging. Therefore, the goals of this study are to, first, propose a simple IVUS imaging–specific method for tracking the displacement of groups of pixels of interest in sequential IVUS images of the artery under different intraluminal pressures and, second, to evaluate the accuracy of the method through the use of a numerical phantom. The tracking method is based on a Block Matching framework, comparing two distinct frames within a selected region by normalized cross-correlation. Our method, specialized for IVUS applications, reduced the tracking area by implementing a limiting radius and a directional bias during the search. The method was evaluated by using 54 numerical phantom image sequences from 9 distinct arterial models, resulting in different arteries with atherosclerotic plaques under a range of pressures. The mean absolute tracking errors ± SD for our method were 15.56 ± 19.46 μm and 13.04 ± 13.82 μm for the horizontal and vertical directions, respectively, between 2 subsequent frames, and 162.58 ± 305.93 μm and 102.22 ± 130.61 μm from lower to higher pressures in the range of 6 frames. Compared to errors of 98 ± 84 μm and 55 ± 44 μm, and 104 ± 127 μm and 29 ± 57 μm, shown in the literature, we can verify that the proposed speckle tracking method shows better accuracy in IVUS images than other current tracking methods.
- ItemSomente MetadadadosA avaliação da acurácia diagnóstica da elastografia bidimensional por ondas de cisalhamento (2D SWE) na diferenciação entre nódulos tireoidianos benignos e malignos(Universidade Federal de São Paulo (UNIFESP), 2020-07-30) Carneiro Filho, Raimundo Airton Holanda [UNIFESP]; Iared, Wagner [UNIFESP]; Universidade Federal de São PauloObjectives: To evaluate two-dimensional (2D) shear wave elastography (SWE) performance as an independent predictor of malignancy in the diagnostic differentiation of thyroid nodules (TNs), including subgroup analyses of different manufacturers and respective cutoffs points. Methods: The online databases MEDLINE (PubMed), Embase, and the Cochrane Library were searched for articles using 2D SWE in TN evaluation. After good-quality relevant thyroid-specific articles were selected, the main data, plus their sensitivity and specificity, were tabulated. A meta-analysis was performed to obtain summary data on sensitivity and specificity of 2D SWE for the differentiation between benign and malignant TNs. Summary receiver operating characteristic curves were generated to compare the accuracy of data obtained from 3 manufactures. Results: The summary data of sensitivity and specificity parameters of 2D SWE for the differentiation between benign and malignant TNs according to different instruments were, respectively, as follows: SuperSonic SWE (SuperSonic Imagine, Aix-en-Provence, France), 0.63 (95% CI, 0.59–0.66) and 0.81 (95% CI, 0.79–0.83); Virtual Touch tissue imaging and quantification (Siemens Medical Solutions, Mountain View, CA), 0.72 (95% CI, 0.67–0.77) and 0.81 (95% CI, 0.78–0.84); and Toshiba SWE (Toshiba Medical Systems, Tochigi, Japan), 0.77 (95% confidence interval [CI], 0.70–0.83) and 0.76 (95% CI, 0.72–0.81). The summary receiver operating characteristic curves showed the following area under the curve syntheses: SuperSonic SWE, 0.88 (Q* = 0.8102); Virtual Touch tissue imaging and quantification, 0.85 (Q* = 0.7809); and Toshiba SWE, 0.84 (Q* = 0.7707). Positive and negative predictive values varied, respectively, from 16% to 94% and 29% to 100%, considering all included articles. The overall accuracy ranged from 53% to 93%. Conclusions: Two-dimensional SWE can be raised as a relevant diagnostic tool that supports ultrasound in clinical practice in the differentiation between benign and malignant TNs.
- ItemAcesso aberto (Open Access)Avaliação da Fibrose Hepática por Elastografia nos pacientes portadores de Esquistossomose Mansônica(Universidade Federal de São Paulo (UNIFESP), 2019-06-11) Lima, Leila Maria Soares Tojal De Barros [UNIFESP]; Parise, Edison Roberto [UNIFESP]; Lacet, Celina Maria Costa [UNIFESP]; http://lattes.cnpq.br/2511547113985954; http://lattes.cnpq.br/8624120197731317; Universidade Federal de São Paulo (UNIFESP)Introduction: Schistosomiasis persists as an important public health problem. Its main pathogenic event is hepatic fibrosis, associated with disease progression and its prognosis. The applicability of hepatic elastography in the evaluation of schistosomal fibrosis remains undefined. Objectives: To correlate the degree of fibrosis obtained by transient liver elastography (TE) with sonographic graduation and clinical forms of patients with schistosomiasis mansoni (SM). Methods: A cross sectional study with prospective inclusion of patients with SM, in all its forms, coming from the hepatology outpatient clinic of the University Hospital of the Federal University of Alagoas and from active search in Alagoas municipalities with high endemicity. Clinical and laboratory characteristics (clinical form, AST dosage, ALT, gammaGT, alkaline phosphatase and platelet count) were evaluated. The patients were classified according to the degree of hepatic fibrosis of the Niamey sonographic protocol, adopted by the World Health Organization, gold standard in this study. The TE, performed with FIBROSCAN ECHOSENS 502 device, was correlated with sonographic findings and its performance was calculated as area under the ROC curve (AUC). Results: A total of 117 patients with schistosomiasis mansoni, 55.6% female and 44.4% male, with mean age of 47 + 15 years were studied, 37 patients with intestinal forms, 12 with hepatointestinal form and 68 with compensated hepatosplenic form. Applying the Niamey sonographic protocol, the patients were regrouped for a better statistical analysis in absent fibrosis (A) 34.2%, mild to moderate fibrosis (MM) 27.4% and intense fibrosis (I) 38.5% of the sample. The median value of TE in the entire study population was 8.0 kPa; in the hepatointestinal form 4.4 kPa, in the hepatointestinal form 5.8 kPa and in the hepatosplenic form 10.6 kPa, with statistical differentiation between the clinical forms (p<0.01). In the correlation between TE and ultrasonography (US), patients in group A presented a median of 4.7 kPa; group MM 9.3 kPa and group I 10.3 kPa. There was a significant difference in TE values between groups A and MM and between groups A and I (p <0.05). TE was not able to differentiate patients from the MM and I groups. In the bivariate analysis between the markers of fibrosis and the clinical and laboratory characteristics, the TE and the sonographic classification of Niamey showed a strong and direct correlation with the clinical form (r>=0.77) and moderate and direct with the levels of AST and GGT (0.45<=r<=0.56). The cut-off point of TE to define the presence of fibrosis according to the sonographic classification that presented the best sensitivity and specificity ratio was 6.1 kPa (AUC 0.92) and for advanced fibrosis 8.9 kPa (AUC 0.791). Conclusions: The TE had a direct correlation with the sonographic classification of Niamey and was able to differentiate the clinical forms of SM. Based on the AUC value, TE has proven to be effective in detecting the presence of schistosomiasis fibrosis and may assist in the identification of advanced forms of liver disease caused by Schistosoma mansoni.