379 research outputs found
High-frame-rate coherence imaging of the heart with ultrasound diverging waves
No full textSeveral techniques have been proposed up to now to achieve higher temporal resolution in echocardiography. Among these, the use of diverging beams, which insonify a large region of interest, allows to significantly increase the frame-rate, but at the cost of a reduced signal-to-noise ratio. For this reason, in this paper we propose to combine high-frame-rate imaging, by transmitting diverging waves (DWs), to the Short-Lag Spatial Coherence (SLSC) technique in reception, which provides images of the coherence of backscattered echoes and is known to yield improved contrast in scenarios with high-clutter. We test this combined method first on phantom acquisitions and then on in vivo cardiac scans, i.e. on apical views of the heart. Results show that SLSC can provide improved contrast ratio (CR) and generalized contrast-to-noise ratio (GCNR) with respect to the classic Delay and Sum (DAS) as the number of transmitted DWs increases, particularly when clutter is present. Indeed, cardiac images show improved apex visibility and artifact suppression in the heart chambers with SLSC, achieving high contrast and high frame-rate at the same time
Numerical Simulation of Liquid-Structure Interaction Problems in a Tank for Aerospace Applications
No full textNumerical Simulation of Liquid-structure Interaction Problem in a Tank of a Space Re-entry Vehicle
No full textNon
Experimental evaluation of ultrasound higher-order harmonic imaging with Filtered-Delay Multiply And Sum (F-DMAS) non-linear beamforming
No full textTissue Harmonic Imaging (THI) mode is currently one of the preferred choices by the clinicians for its ability to provide enhanced ultrasound images, thanks to the use of the second harmonic component of backscattered echoes. This paper aims at investigating whether the combination of THI with Filtered-Delay Multiply And Sum (F-DMAS) beamforming can provide further improvements in image quality. F-DMAS is a new non-linear beamformer, which, similarly to THI, is based on the use of the second harmonics of beamformed signals and is known to increase image contrast resolution and noise rejection. Thus, we have first compared the images obtained by using F-DMAS and the standard Delay And Sum (DAS) beamformers when only the second harmonics of the received signals was selected. Moreover, possible improvements brought about by other harmonic components generated by the combined use of the fundamental plus second harmonics and F-DMAS beamforming have been explored. Experimental results demonstrate that, as compared to standard harmonic imaging with DAS, THI and F-DMAS can be joined to improve the 20 dB lateral resolution up to 1 mm, the contrast ratio up to 12 dB on a cyst-phantom and up to 9 dB on in vivo images
Enhanced ultrasound harmonic imaging using the filtered-delay multiply and sum beamformer
No full textUltrasound Tissue Harmonic Imaging (THI) exploits the second harmonic component of backscattered signals generated by non-linear propagation in tissues. Compared to standard fundamental imaging mode, THI provides images with improved resolution and contrast, but with lower signal-to-noise ratio (SNR). The Filtered-Delay Multiply And Sum (F-DMAS) non-linear beamformer was recently demonstrated able to produce images with significantly superior contrast resolution and noise rejection than conventional Delay And Sum (DAS). In this work we experimentally investigate whether the combination of THI with F-DMAS can further suppress beam side-lobes and noise to provide enhanced image quality. Experimental images acquired on phantoms show that, when F-DMAS is applied, resolution and contrast improve and the SNR increases
Design Candidate Identification via Kansei-VR & AHP approaches
No full textIn this work the Authors show the first results of a research activity aiming at the identification of the most appealing design candidate via a new integrated Kansei Engineering process. The target was achieved by means of immersive experiments performed in Virtual Reality (VR) along with an Analytic Hierarchy Process (AHP) performed in a visual desktop environment (PC). Both the approaches aim at the direct involvement of users into the design process, as early as possible.
Focusing on the synthesis phase, once implemented the design candidates by different technical features according to a Fractional Factorial Design, the concepts are evaluated by users. The data collected by asking users to judge them are analyzed via suitable methods to guarantee the above assessment. For this purpose, two different evaluation approaches, although at different stages of the design process, are tested: the first one relies on the user experience with the product in VR whereas the second is allowable for a much cheaper visual pairwise comparison in a PC-based experimental set-up. The original result is that the two approaches can be complementary rather than alternative; here is introduced the way to harmonize them in an integrated Kansei Engineering process, in order to improve and speed-up the synthesis phase.
To describe the two approaches and highlight their peculiarities, an application to the design of railway coach arrangement and furniture (briefly referred to as “train interior”) is presented
Apoptosis and in vitro Alzheimer disease neuronal models
No full textAlzheimer disease (AD) is a human neurodegenerative disease characterized by co-existence of extracellular senile plaques (SP) and neurofibrillary tangles (NFT) associated with an extensive neuronal loss, primarily in the cerebral cortex and hippocampus. Several studies suggest that caspase(s)-mediated neuronal death occurs in cellular and animal AD models as well as in human brains of affected patients, although an etiologic role of apoptosis in such neurodegenerative disorder is still debated. This review summarizes the experimental evidences corroborating the possible involvement of apoptosis in AD pathogenesis and discusses the usefulness of ad hoc devised in vitro approaches to study how caspase(s), amyloidogenic processing and tau metabolism might reciprocally interact leading to neuronal death
- …
