| 1. |
- Erlöv, Tobias, et al.
(författare)
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A robust and fast method for arterial lumen diameter and intima-media thickness measurements
- 2012
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Ingår i: 2012 IEEE International Ultrasonics Symposium (IUS). - 9781467345613 - 9781467345620 ; , s. 1678-1681
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Konferensbidrag (refereegranskat)abstract
- Lumen diameter, distension and intima-media thickness (IMT) in human arteries are important parameters in cardiovascular research. The signal reflected from the arterial wall strongly depends on the ultrasound scanner and settings. The signal also varies with age and health of the subject. A general method insensitive with respect to the subject and the scanner would be of great help. We have developed a novel and robust method for ARTerIal Characterization (ARTIC), suitable for real-time in vivo measurements of diameter, distension and IMT using B-Mode images. The aim of this study was to evaluate ARTIC on different subjects and scanners. ARTIC was evaluated in vivo in different groups of subjects using two scanners, HDI5000 (Philips Medical Systems, Bothell, WA, USA) and ULA-OP (University of Florence, Italy). First, a comparison was made against a previous method validated on phantoms. Then measurements of young (healthy) and old (healthy and unhealthy) subjects were evaluated for both scanners. Finally, a comparison between scanners was made. The evaluation of different subjects shows a coefficient of variation (CV) ranging from 1.4-2.0% for diameter, 4.3-8.8% for distension and 3.6-6.6% for IMT.
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| 2. |
- Larsson, Matilda, et al.
(författare)
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Carotid strain estimation using an ultrasound-based speckle tracking algorithm
- 2012
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Ingår i: 2012 IEEE International Ultrasonics Symposium (IUS). - : IEEE. - 9781467345613 ; , s. 1394-1397
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Konferensbidrag (refereegranskat)abstract
- Carotid strain imaging using ultrasound-based speckle tracking has showed potential in risk stratification of cardiovascular diseases. However, assessing strain in the artery wall and in atherosclerotic plaques is challenging because of small dimensions and low deformations in relation to the applied ultrasound wavelength. High-resolution ultrasound has potential to improve the speckle tracking performance by increasing spatial resolution. The aim of this study was to compare carotid strain estimation by speckle tracking using standard clinical ultrasound and high-resolution ultrasound in an experimental setup. Ultrasound long-axis images were obtained using a standard clinical ultrasound system (Vivid7) and a high-resolution ultrasound system (Vevo2100) in dynamic phantoms mimicking the carotid artery. Speckle tracking was performed to estimate radial and longitudinal strain whereas sonomicrometry was used as reference. The results showed a significant better performance for speckle tracking applied on images from the high-resolution system compared to the standard clinical system.
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| 3. |
- Ricci, S., et al.
(författare)
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Volume flow assessment through simultaneous B-mode and Multigate Doppler
- 2012
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Ingår i: 2012 IEEE International Ultrasonics Symposium, IUS 2012. - 9781467345613 - 9781467345620 ; , s. 1588-1591
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The typical approach for volumetric blood flow assessment consists of a velocity measurement performed in a single sample volume placed in the vessel centre, combined to an estimate of the average diameter. This simple approach produces large inaccuracies since it does not account for the complex flow configurations produced by complicated artery geometries and/or pulsatile conditions. Moreover, diameter changes, which in important regions like the common carotid artery can be larger than 10%, are totally neglected. In this work we propose an alternative volume flow method which overcomes some of the aforementioned limitations through the simultaneous measurement of the wall positions and of the velocity distribution in the artery. The wall positions are tracked by a detector based on the First Order Absolute Moment working on B-mode data, while the velocity profile is obtained by a Multigate Spectral Doppler analysis applied to PW-mode data. The method was implemented on the ULA-OP research system and validated on a flow phantom with more than 1700 experiments performed in rigid and flexible pipes. We found a systematic underestimation of 3.7% with 5.0% standard deviation. The mean coefficient of variation (CV) was 1.7%.
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| 4. |
- Widman, Erik, et al.
(författare)
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Shear wave elastography for characterization of carotid artery plaques-A feasibility study in an experimental setup
- 2012
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Ingår i: 2012 IEEE International Ultrasonics Symposium (IUS). - : IEEE. - 9781467345613 ; , s. 6562400-
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Konferensbidrag (refereegranskat)abstract
- Characterization of vulnerable plaques in the carotid artery is critical for the prevention of ischemic stroke. However, ultrasound-based methods for plaque characterization used in the clinics today are limited to visual assessment and evaluation of plaque echogenicity. Shear Wave Elastography (SWE) is a new tissue characterization technique based on radiation force-induced shear wave propagation with potential use in plaque vulnerability assessment. The purpose of this study was to develop an experimental setup to test the feasibility of SWE for carotid plaque characterization. A carotid artery phantom with a soft inclusion in the wall, mimicking a vulnerable plaque, was constructed (10% polyvinyl alcohol (PVA), 3% graphite) by exposing the vessel and plaque to three and one freeze-thaw cycles (6h freeze, 6h thaw) respectively. An Aixplorer SWE system (Supersonic Imagine) was used to measure the shear wave speed (cT) in the vessel wall and plaque. The Young's modulus (E) was then calculated via the Moens-Korteweg (M-K) equation. For comparison, eight cylinders (d = 4 cm, h = 4 cm) were constructed for mechanical testing from the same PVA batch, of which four were exposed to three freeze-thaw cycles (mimicking the vessel wall) and four to one freeze-thaw cycle (mimicking the plaque). The Young's moduli for the cylinders were obtained via a displacement controlled mechanical compression test (Instron 5567) by applying 5% strain. The mean shear wave speed was 2.6 (±0.7) m/s in the vessel wall, 1.8 (±0.7) m/s in the plaque, resulting in Evessel = 11.5 (±0.5) kPa, Eplaque = 4.3 (±0.5) kPa. The compression tests resulted in E = 64.2 (±11.1) kPa in the hard cylinder and E = 9.7 (±3.1) kPa in the soft cylinder. The results showed that it was possible to distinguish between the arterial wall and the plaque. The disagreement between mechanical testing and SWE can be explained by the fact that the shear wave does not propagate monochromatically in cylindrical geometry. To achieve a better calculation of the elastic modulus, the frequency dependency of the shear wave velocity must be considered.
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| 5. |
- Yantchev, Ventsislav, et al.
(författare)
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Parametric Study of Thin-film Zero-Group Velocity Resonators
- 2012
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Ingår i: 2012 IEEE International Utrasonics Symposium (IUS). - 9781467345613 ; , s. 307-310
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Konferensbidrag (refereegranskat)abstract
- Here we demonstrate experimentally a novel, small form factor, resonant architecture employing the intrinsic zero-group-velocity dispersion of the first order symmetric Lamb wave S1 propagating in piezoelectric AlN film membranes. Designs with different topologies were fabricated and compared. FEM analysis is used to verify the observed differences while providing a deeper insight to the resonator performance. Technique for improvement of the device performance are further proposed.
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