Search results for "ULTRASOUND"
showing 10 items of 1259 documents
Inspection of additive-manufactured layered components
2015
Laser powder deposition (LPD) is a rapid additive manufacturing process to produce, layer upon layer, 3D geometries or to repair high-value components. Currently there is no nondestructive technique that can guarantee absence of flaws in LPD products during manufacturing. In this paper a laser ultrasonic technique for in-line inspection of LPD components is proposed. Reference samples were manufactured from Inconel and machined flaws were created to establish the sensitivity of the technique. Numerical models of laser-generated ultrasonic waves have been created to gain a deeper understanding of physics, to optimize the set-up and to verify the experimental measurements. Results obtained on…
A 2D-FEM Model of Nonlinear Ultrasound Propagation in Trans-cranial MRgFUS Technique
2022
Magnetic Resonance guided Focused Ultrasound (MRgFUS) is a non-invasive technique based on the thermal ablation of a target using high intensity focused ultrasound. MRgFUS treatment applied to brain is challenging due to the skull presence that attenuates ultrasound, leading to heating effects in bone region. In this study, we simulate trans-cranial nonlinear ultrasound propagation considering the detailed structure of bone tissue. We developed a 2D Finite Element (FE) model that mimics the propagation of focused ultrasound through skin, skull and brain tissue. The skull is represented as a three-layered system with two cortical tables packing a layer of trabecular bone. We assume that the …
Learning With Context Feedback Loop for Robust Medical Image Segmentation
2021
Deep learning has successfully been leveraged for medical image segmentation. It employs convolutional neural networks (CNN) to learn distinctive image features from a defined pixel-wise objective function. However, this approach can lead to less output pixel interdependence producing incomplete and unrealistic segmentation results. In this paper, we present a fully automatic deep learning method for robust medical image segmentation by formulating the segmentation problem as a recurrent framework using two systems. The first one is a forward system of an encoder-decoder CNN that predicts the segmentation result from the input image. The predicted probabilistic output of the forward system …
Critical comments on EEG sensor space dynamical connectivity analysis
2019
Many different analysis techniques have been developed and applied to EEG recordings that allow one to investigate how different brain areas interact. One particular class of methods, based on the linear parametric representation of multiple interacting time series, is widely used to study causal connectivity in the brain. However, the results obtained by these methods should be interpreted with great care. The goal of this paper is to show, both theoretically and using simulations, that results obtained by applying causal connectivity measures on the sensor (scalp) time series do not allow interpretation in terms of interacting brain sources. This is because (1) the channel locations canno…
Application of ultrasound as clean technology for extraction of specialized metabolites from stinging nettle (Urtica dioica L.)
2022
Nettle is a highly valued medicinal plant that is still largely neglected, both in terms of nutrition and use for pharmacological purposes. Tinctures, i.e., alcoholic extracts, are becoming increasingly popular nettle products, mainly because they allow better availability of phytochemicals and their stability over a longer period of time. The production of alcoholic extracts is a chemically demanding process that is still usually carried out using conventional techniques, which have numerous drawbacks. The use of green technologies such as ultrasound-assisted extraction (UAE), which is characterized by high efficiency of phytochemical extraction, shorter treatment time, and a much lower en…
Ultrasonic mensuration of fetal limb bones in the second and third trimesters
1987
Growth of fetal limb bones has been examined in a prospective cross-sectional study in 530 patients between 13 and 42 weeks of gestation by ultrasound. The length of the femur, tibia, humerus, and radius were measured in all cases, and fibula and ulna in 393 cases. For each week of gestation mean lengths (+/- 2 standard deviations) were calculated. All limb bones showed linear growth from 13 weeks to 25 weeks of gestation, after which the growth curve appeared nonlinear. A strong linear relationship (r greater than 0.98) between the BPD and bone length was found for each bone. In five aborted fetuses, prenatal sonographic measurements of the ossified diaphyses were compared with the postnat…
Value of the electronic scalpel (cut mode) in the evaluation of the fetal face
2000
Objectives To evaluate the improvement of image quality and diagnostic value of fetal face examinations using the electric scalpel. Methods A total of 232 cases were examined. The fetuses were separated into two groups: Group A, including normal fetuses (n = 152) and Group B, fetuses with facial pathology (n = 80). The fetuses were divided into eight subgroups according to gestational age (9–12 weeks, 13–16 weeks, 17–20 weeks, 21–24 weeks, 25–28 weeks, 29–32 weeks, 33–36 weeks and 37–40 weeks). Results The number of cutting steps for the improvement of image quality ranged from 1 to 9 (mean value 3) in the group of normal fetuses and from 1 to 10 (mean value 3) in the group of fetuses with …
An anatomical fetal brain structure and a normal variant mimicking anomalies on routine neurosonographic imaging: report of two cases
2004
We present two cases in which an anatomical structure, the calcar avis, and a normal variant, a bifid choroid plexus, mimicked abnormalities on routine prenatal ultrasound examination. To the best of our knowledge these pitfalls have only been described in neonates. A familiarity with these false images is important to avoid erroneous diagnoses.
Biometry of the fetal corpus callosum by three-dimensional ultrasound
2013
Objectives To construct reference ranges of quantitative characteristics of the fetal corpus callosum. Methods Women referred to a tertiary center for sonographic examination were recruited to undergo a detailed fetal scan from 17 to 41 weeks of gestation. Three-dimensional (3D) sonographic volumes of normal fetal brains were acquired and analyzed offline. We obtained three different measurements of the corpus callosal length, as well as the height (/thickness) of its segments, namely the rostrum, genu, body and splenium. Results Initially we recruited 604 pregnant women, of whom 138 were excluded because of various disorders/abnormalities, multiple pregnancy or gestational age < 18 weeks. …
Entwicklung eines Wachstumsmodells für fetale Kopf- und Rumpfmaße
1987
Head parameters BPD, FOD and HC and abdomen parameters ATD, APD and AC have been ascertained in a prospective cross-sectional study in 515 healthy single fetuses between 13 and 40 weeks of gestation by ultrasound. In all cases ultrasound velocity was 1540 m/sec. From these data, a growth model was achieved for each parameter and corresponding growth curves with 5%, 10%, 50%, 90% and 95% percentiles were established.