The Infona portal uses cookies, i.e. strings of text saved by a browser on the user's device. The portal can access those files and use them to remember the user's data, such as their chosen settings (screen view, interface language, etc.), or their login data. By using the Infona portal the user accepts automatic saving and using this information for portal operation purposes. More information on the subject can be found in the Privacy Policy and Terms of Service. By closing this window the user confirms that they have read the information on cookie usage, and they accept the privacy policy and the way cookies are used by the portal. You can change the cookie settings in your browser.
The combination of refined medical imaging techniques and computational fluid dynamics (CFD) models has enabled the study of complex flow behavior on a highly regional level. Recently, we have developed a platform for patient-specific CFD modelling of blood flow in the left ventricle (LV), with input data and required boundary conditions acquired from 4D echocardiography. The platform robustness has...
Ultrasensitive Doppler is a recent medical imaging technique enabling high sensitive acquisition of blood flows which can detect small vascular features without contrast agents. Applied to cerebral imaging of rodents, this method produces very fine vascular maps of the brain at high spatial resolution and leads to functional imaging of brain neuronal activity. These vascular networks contain crucial...
Spectral broadening in pulsed wave Doppler caused by the transit time effect deteriorates the frequency resolution and may cause overestimation when tracing the maximum velocities in high velocity blood flow regions. Data adaptive spectral estimators have been shown to provide improved frequency resolution, especially for small window sizes, but offer little or no improvement when the transit time...
The recent introduction of functional ultrasound (fUS) based on ultrafast Doppler imaging for blood flow detection unveiled a gigantic field of applications in Neuroimaging. Its considerable sensitivity, temporal and spatial resolution enabled to image the neurovascular coupling in unprecedented situations such as olfactory stimulation or spatial representation in an awake animal. However, to date...
Assessment of perfusion adaptation in muscle during exercise can provide diagnostic information on cardiac and endothelial diseases. Power Doppler Ultrasound (PDUS) is known for its feasibility in the non-invasive measurement of moving blood volume (MBV), a perfusion related parameter. In this study, we show how PDUS can be used to assess the MBV kinetics in muscle, before, during, and after exercise...
The maximum velocity of blood flow is the primary means for determining the degree of stenosis in the carotid artery. The current standard for estimating the maximum velocity is Pulsed Wave (PW) Doppler with manual angle correction, assuming that the flow is parallel to the vessel wall. This assumption is not always correct, leading to errors in the velocity estimates and potentially in the assessment...
Microbubble cavitation is key dynamics of ultrasound assisted drug delivery system (US-DDS). However, its mechanism is too complicated to control due to bubble cloud formation under US irradiation. In US-DDS, a feed-back system which monitors bubble cavitation in-situ and optimizes the US irradiation sequence according to the bubble characteristics, such as the sensitivity of bubble to US wave and...
Standard Doppler ultrasound investigations are limited to detect the axial blood velocity component, as they cannot directly estimate the flow direction. A typical approach for obtaining velocity vectors consists in combining the Doppler shifts detected by receiving the echoes from two (or more) different directions. Together with plane wave transmission, this strategy can assess the velocity data...
The peak velocity of the blood flowing in carotid is a parameter of high impact in the diagnosis of cardiovascular diseases. Current measurement methods are based on heuristic thresholds applied to the Doppler spectrum. Unfortunately, they often produce inaccurate assessments due to their sensitivity to noise and to the spectral broadening effect. Recently, a new vector technique has been proposed...
Clinical ophthalmic ultrasound is currently performed with mechanically scanned, single-element probes, but these are unable to provide useful information about blood flow with Doppler techniques. Linear arrays are well-suited for the detection of blood flow, but commercial systems generally exceed FDA ophthalmic safety limits. A high-speed plane-wave ultrasound approach with an 18-MHz linear array...
Various quantitative ultrasound techniques allow the estimation of elastic parameters in tissues using mechanical or acoustic radiation forces. However, it has previously been reported that the presence of phase aberration compromises elasticity measurement results when propagating in inhomogeneous media. In this study, a comparative evaluation of the effects of phase aberration when estimating shear...
In this paper, conventional B-mode imaging and pulsed Doppler were employed to investigate spatial-temporal distribution of residual cavitation bubbles generated by pHIFU thrombolysis within a vessel. The HIFU pulse sequences had various acoustic parameters including pulse duration (PD = 10, 20, 30 µs), duty cycle (DC = 1∶10, 10∶20, 1∶30) and the number of pulses (n = 5, 10, 20). A non-transparent...
Implementation of 3D high frame rate (HFR) tissue Doppler imaging (TDI) typically requires a fully wired matrix probe. However, such probes remain impractical for use in a clinical setting. Therefore, clinical matrix arrays rely on sub-aperture (SAP) beamforming. This makes diverging wave (DW) imaging challenging as side- and grating-lobes arise from the simultaneous reconstruction of image lines...
Biomechanical assessment of atherosclerosis has been mainly studied by tissue characterization and elasticity measurement of arterial wall in biomedical ultrasound. On the other hand, fluid shear stress on the artery is also known as an important factor to change vascular endothelium properties leading to atherosclerosis. Ultrasound is a suitable imaging modality to measure blood flow with high temporal...
Large-scale functional imaging techniques are part of a fast growing field of neuroscience aiming at understanding whole brain activity. The recently introduced Functional Ultrasound Imaging (fUS), based on ultrafast Doppler, is a new very sensitive method monitoring changes in slow blood flow with a high spatial (∼100µm) and temporal (down to the cardiac time scale) resolution for a typical imaged...
Vector Flow Imaging (VFI) has received an increasing attention in the scientific field of ultrasound, as it enables angle independent visualization of blood flow. VFI can be used in volume flow estimation, but a vessel segmentation is needed to make it fully automatic. A novel vessel segmentation procedure is crucial for wall-to-wall visualization, automation of adjustments, and quantification of...
This research presents a damage detection technique based on a compressive sensing (CS) algorithm applied to full wavefield data. The aim is to realize an effective tool for damage detection and localization which allows to reduce the acquisition time. The proposed technique exploits the compressive sensing framework to infer the damage location and entity from the comparison between the wavefield...
The Transmission of Plane Waves (PWT) has recently promoted the development of “ultrafast” Doppler applications. The inherent high computation cost has typically enabled retrospective implementations, i.e. the acquisition of raw data followed by fast off-line beamforming and Doppler processing. In this paper, the combination of PWT with real-time beamforming and Color Flow Mapping (CFM) is experimentally...
Perfusion imaging with conventional Doppler ultrasound is difficult due to frame rate and tissue clutter limitations. Consequently, conventional methods are only sensitive to velocities above 5–10mm/s for typical clinical imaging frequencies. To overcome this limitation and simultaneously address the frame rate and tissue clutter problems, we propose a technique that uses plane wave sequencing and...
Set the date range to filter the displayed results. You can set a starting date, ending date or both. You can enter the dates manually or choose them from the calendar.