1,723,014 research outputs found
Simulated Cervical ARFI
No full textEvery day, 1,300 children in the U.S. and an additional 34,000 children worldwide are born prematurely. This study acts as a feasibility study for a proposed ultrasonic technique for the identification of preterm birth risk factors using an acoustic technique known as Acoustic Radiation Force Impulse (ARFI) imaging. A 3D finite element model was constructed to optimize transducer ARFI parameters in a layered cervix structure prior to clinical evaluation. The transducer model optimized in this study was the AcuNavTM (Siemens Medical Solutions, Mountain View, CA). Cervix model structural geometry and material properties were varied according to anticipated pregnancy induced property fluctuation. Transmitted ARFI acoustic fields were generated by applying a Field II derived pulse to the 3D model[15]. Optimization procedures were performed in the following order: focal depth evaluation, transmit frequency optimization, effect of material property variation and the application of ARFI shear wave speed calculation algorithms to a layered cervical structure. Results indicated that ARFI evaluation of a layered cervix structure was most feasible using an 8MHz transmit frequency in the focal range of 5-10mm axial depth. It was observed that material property estimation errors were most likely when ARFI excitations were focused near a material boundary. A phenomenon was noted where shear waves initiated in stiffer media were slowed as a function of their relative proximity to a more compliant medium. Overall, these simulation studies demonstrate that ARFI shear wave imaging in the cervix is feasible; a model has been developed that can be used to evaluate the accuracy of shear stiffness estimates in the cervix to help address the important clinical problem of premature cervical ripening.</p
The diagnostic performance of ARFI in staging cirrhosis (F = 4).
No full text(A) Forest plot for the pooled estimates of sensitivity and specificity of ARFI on the differentiation of cirrhosis. (B) Fagan nomogram for the differentiation of hepatic cirrhosis with ARFI. (C) The summary receiver operating curve (SROC) and corresponding area under ROC (AUROC) for the differentiation of hepatic cirrhosis with ARFI. (D) SROC curve and corresponding AUROC for the differentiation of hepatic cirrhosis with ARFI in patients with NAFLD or NASH.</p
Применение ARFI-эластографии для оценки жесткости паренхимы щитовидной железы у детей, подростков и молодых взрослых
Full text linkIntroduction. Thyroid diseases occupy the first place in the overall structure of endocrine diseases in children and adolescents. A problem is the objectification of the results of the subsidiary methods. One of the ways to improve ultrasound techniques - development of elastography. Purpose. Determine the velocity of the shear wave propagation (ARFI-elastography) in the parenchyma of the thyroid in children and adolescents without endocrine pathology. Material and methods. Ultrasound researches of the thyroid gland were made in 195 children and adolescents. Results. For children up to 1.5 years the average value of ARFI was 1.3 m/s (range 0.9-2.3), increasing to 2.3 (1.7-3.6) in people aged 22 years and older. Age dynamics in the shear wave velocity consistent with the morphological changes. Conclusion. Shear wave velocity (ARFI-elastography) can be used as normative. Increasing the speed of the shear wave propagation in older people reflects age-related changes of the thyroid gland parenchyma.Введение. Заболевания щитовидной железы занимают первое место в общей структуре эндокринной патологии у детей и подростков. Актуальна задача объективизации результатов вспомогательных методов исследования. Одно из направлений - развитие УЗИ-эластографии. Цель исследования: определить скорость распространения сдвиговой волны (ARFI-эластография) в паренхиме щитовидной железы у детей и подростков без эндокринной патологии. Материал и методы. Проведено УЗИ щитовидной железы 195 пациентам в возрасте от 1,5 до 27 лет. Результаты. Для детей до 3 лет средняя величина ARFI составила 1,3 м/с (пределы колебаний 0,9-2,3), постепенно увеличиваясь до 2,3 (1,7-3,6) у людей в возрасте 22 лет и старше. Возрастная динамика показателя скорости сдвиговой волны соответствует известным морфологическим изменениям. Выводы. Показатели скорости сдвиговой волны (ARFI-эластография) могут использоваться как нормативные. Увеличение скорости распространения сдвиговой волны отражает возрастные изменения паренхимы щитовидной железы
Receiver-operating characteristic (ROC) curves for ARFI-imaging of thyroid nodule (ARFI-nod) and for the ratio of ARFI-imaging of thyroid nodule divided by ARFI-imaging of healthy thyroid tissue (ARFI-rat) for diagnosis of malignant thyroid nodules (AUROC 69% and 71%, respectively) and the ROC curves for the combination of these criteria with Realtime Elastography Score (ES) 3–4 (AUROC 78% and 78%, respectively).
No full text<p>The improvements with respect to ARFI alone were not significant (p = 0.18 for ARFI-nod, p>0.20 for ARFI-rat), analogously the improvements with respect to ES alone were not significant (p>0.20 in both cases).</p
Cylindrical Transducer for Intravascular ARFI Imaging: Design and Feasibility
No full textIntravascular acoustic radiation force impulse (IV-ARFI) imaging has the potential to identify vulnerable atherosclerotic plaques and improve clinical treatment decisions and outcomes for patients with coronary heart disease. Our long-term goal is to develop a thin, flexible catheter probe that does not require mechanical rotation to achieve high-resolution IV-ARFI imaging. In this work, we propose a novel cylindrical transducer array design for IV-ARFI imaging and investigate the feasibility of this approach. We present the construction of a 2.2-mm-long, 4.6-Fr cylindrical prototype transducer to demonstrate generating large ARFI displacements from a small toroidal beam, and we also present simulations of the proposed IV-ARFI cylindrical array design using Field II and a cylindrical finite-element model of vascular tissues and soft plaques. The prototype transducer was found to generate peak radial displacements of over 10~\mu \text{m} in soft gelatin phantoms, and simulations demonstrate the ability of the array design to obtain ARFI images and distinguish soft plaque targets from surrounding, stiffer vessel wall tissue. These results suggest that high-resolution IV-ARFI imaging is possible using a cylindrical transducer array
ARFI-prepared MRgHIFU in liver: simultaneous mapping of ARFI-displacement and temperature elevation, using a fast GRE-EPI sequence
No full textMR acoustic radiation force imaging (ARFI) is an elegant adjunct to MR-guided high intensity focused ultrasound for treatment planning and optimization, permitting in situ assessment of the focusing and targeting quality. The thermal effect of high intensity focused ultrasound pulses associated with ARFI measurements is recommended to be monitored on line, in particular when the beam crosses highly absorbent structures or interfaces (e.g., bones or air-filled cavities). A dedicated MR sequence is proposed here, derived from a segmented gradient echo-echo planar imaging kernel by adding a bipolar motion encoding gradient with interleaved alternating polarities. Temporal resolution was reduced to 2.1 s, with in-plane spatial resolution of 1 mm. MR-ARFI measurements were executed during controlled animal breathing, with trans-costal successively steered foci, to investigate the spatial modulation of the focus intensity and the targeting offset. ARFI-induced tissue displacement measurements enabled the accurate localization, in vivo, of the high intensity focused ultrasound focal point in sheep liver, with simultaneous monitoring of the temperature elevation. ARFI-based precalibration of the focal point position was immediately followed by trans-costal MR-guided high intensity focused ultrasound ablation, monitored with a conventional proton resonance frequency shift MR thermometry sequence. The latter MR thermometry sequence had spatial resolution and geometrical distortion identical with the ARFI maps, hence no coregistration was required
Bibliographie des lagunes et du littoral de Côte d'Ivoire (Afrique de l'Ouest)
Full text linkThe present bibliography collects references on lagoon and coastal environments in Côte d'Ivoire. It is mainly based on: - the draft bibliography prepared by Charles-Dominique and Durand in 1979, edited in the Archives Scientifiques du Centre de Recherches Océanographiques d'Abidjan (vol. 5 no. 2); - the synthesis on the marine environment, published in 1993 (LeLoeuff, Marchal and Amon-Kothias editors); - and the synthesis on the lagoon environment, published in 1994 (Durand, Dufour, Guiral and Zabi editors). In spite of a careful check of the available documents, it is more than possible that references are lacking or erroneous. That's why this bibliography is still a draft, and the author will be glad to receive complements and/or corrections from lectors. After these contributions, a more comprehensive version will be proposed. Remarks can be sent to this e-mail: [email protected] or to the postal address
Bibliography of the lagoons and coasts of Côte d'Ivoire (Western Africa)
No full textThe present bibliography collects references on lagoon and coastal environments in Côte d'Ivoire. It is mainly based on: - the draft bibliography prepared by Charles-Dominique and Durand in 1979, edited in the Archives Scientifiques du Centre de Recherches Océanographiques d'Abidjan (vol. 5 no. 2); - the synthesis on the marine environment, published in 1993 (LeLoeuff, Marchal and Amon-Kothias editors); - and the synthesis on the lagoon environment, published in 1994 (Durand, Dufour, Guiral and Zabi editors). In spite of a careful check of the available documents, it is more than possible that references are lacking or erroneous. That's why this bibliography is still a draft, and the author will be glad to receive complements and/or corrections from lectors. After these contributions, a more comprehensive version will be proposed. Remarks can be sent to this e-mail: [email protected] or to the postal address
Usefulness of Liver and Spleen Acoustic Radiation Force Impulse (ARFI) for the evaluation of cirrhotic patients
Full text linkObjective: To evaluate the correlation between ARFI and Child-Pugh classification. Secondary
Aims: 1) To compare ARFI values (hepatic, splenic and spleno-hepatic index) from cirrhotic to
normal population; 2) To correlate biochemical parameters of liver function and ARFI. Materials
and Methods: 58 cirrhotic patients (referenced to US for surveillance or to clarify any hepatic decompensation)
were included in this prospective study, as well as 38 healthy subjects who underwent
ultrasonography for other reasons than hepatic evaluation. All had ARFI liver and spleen
evaluation on ACUSON S2000 ARFI equipment. The best cut-off liver and spleen values for the diagnosis
of cirrhosis in comparison to the normal subjects were determined using SPSS® v20. Results:
Mean liver ARFI values in controls and cirrhotic patients were respectively 1.18 ± 0.22 m/s
and 2.93 ± 0.50 m/s. The ROC curve demonstrated an AUC 0.998 and the best cut-off was 1.89.
Mean spleen ARFI values in controls and cirrhotic patients were respectively 2.60 ± 0.42 m/s and
3.03 ± 0.71. The ROC curve demonstrated an AUC 0.766 and the best cut-off was 2.73 m/s. The
splenohepatic index showed a worse AUC than ARFI liver. A weak correlation was found between
the ARFI liver and Child-Pugh. We found no statistically significant differences for spleen ARFI
values and Child-Pugh. We found a statistically significant correlation between liver ARFI and bilirubin,
ALKP, GGT, AST and AST/ALT ratio; and with spleen ARFI and ALKP and AST/ALT ratio.
Conclusion: We showed that there is a tendency of higher levels of liver ARFI values for higher
Child-Pugh classification suggesting a definite trend for higher values with more severe disease
The diagnostic performance of ARFI in staging severe fibrosis (F≥3).
No full text(A) Forest plot for the pooled estimates of sensitivity and specificity of ARFI on the differentiation of severe fibrosis. (B) Fagan nomogram for the differentiation of severe hepatic fibrosis with ARFI. (C) The summary receiver operating curve (SROC) and corresponding area under ROC (AUROC) for the differentiation of severe hepatic fibrosis with ARFI. (D) Deeks’ funnel plot for the assessment of publication bias. (E) SROC curve and corresponding AUROC for the differentiation of severe hepatic fibrosis with ARFI in patients with liver transplant. (F) SROC curve and corresponding AUROC for the differentiation of severe hepatic fibrosis with ARFI in patients with NAFLD or NASH.</p
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