| 1. |
- Erlöv, Tobias, et al.
(författare)
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A fast 2D tissue motion estimator based on the phase of the intensity enables visualization of the propagation of the longitudinal movement in the carotid artery wall
- 2013
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Ingår i: 2013 IEEE International Ultrasonics Symposium (IUS). - 9781467356855 ; , s. 1761-1764
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Konferensbidrag (refereegranskat)abstract
- A fast 2D motion estimator has been developed and evaluated. The method does not utilize block-matching or iterative solutions and is thus more computationally efficient and suitable for real-time motion estimation over the entire image. The method has been evaluated on 1) phantom measurements and 2) in vivo on the carotid artery wall of 17 subjects, where measurements of the longitudinal displacement of the intima-media complex were compared to our previously validated method. The mean error of the phantom measurements was 2.0 +/- 3.3% (velocities between 2-15 mm/s; approx. 60 million estimations). In the in vivo measurements the mean difference (validated-proposed) was 18 +/- 44 mu m. Further the method has enabled visualization of the propagation of the longitudinal movement in the carotid artery wall. Several different phases of the longitudinal propagation, which seem to be connected to the multi-phasic pattern of the longitudinal movement, can be seen. All phases of the longitudinal propagation seem to originate from the direction of the heart.
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| 2. |
- 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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| 3. |
- Erlöv, Tobias, et al.
(författare)
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Automatic Measurements of Diameter, Distension and Intima Media Thickness of the Aorta in Premature Rabbit Pups Using B-Mode Images.
- 2014
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Ingår i: Ultrasound in Medicine and Biology. - : Elsevier BV. - 0301-5629. ; 40:2, s. 371-377
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Tidskriftsartikel (refereegranskat)abstract
- To improve cardiovascular research, there is a growing need for arterial characterization in small animals. We developed a method, ARTIC (arterial characterization) for measuring lumen diameter, distension and intima media thickness (IMT). In this study ARTIC was used to automatically characterize the aorta of premature rabbit pups. Automatic measurements were compared with manual measurements, both performed by three observers. Diameter was 769 ± 140 μm (manual) and 766 ± 142 μm (automatic), distension was 35 ± 15 μm (manual) and 40 ± 12 μm (automatic) and IMT was 84 ± 11 μm (manual) and 88 ± 8 μm (automatic) (mean ± standard deviation). The variation in the measured diameter, distension and IMT ranged from 1.1% to 26.0% (manual) and from 1.0% to 9.0% (automatic). The intra-class correlation coefficient ranged from 33.0% to 99.3% (manual) and from 76.9% to 99.6% (automatic). The evaluation revealed that it is feasible to use ARTIC on B-mode images of arteries with small dimensions, which makes it a useful tool for arterial characterization in small animals.
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| 4. |
- Erlöv, Tobias, et al.
(författare)
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Determining carotid plaque vulnerability using ultrasound center frequency shifts.
- 2016
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Ingår i: Atherosclerosis. - : Elsevier BV. - 1879-1484 .- 0021-9150. ; 246, s. 293-300
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Tidskriftsartikel (refereegranskat)abstract
- The leading cause of morbidity and mortality worldwide is atherosclerotic cardiovascular disease, most commonly caused by rupture of a high-risk plaque and subsequent thrombosis resulting in stroke, myocardial infarction or sudden death depending on the affected arterial territory. Accurate, non-invasive methods to identify such lesions known as vulnerable or high-risk plaques are currently sub-optimal. Our aim was to validate a new non-invasive ultrasound method to identify high-risk carotid plaques.
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| 5. |
- Rydén Ahlgren, Åsa, et al.
(författare)
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Profound Increase in Longitudinal Displacements of the Porcine Carotid Artery Wall Can Take Place Independently of Wall Shear Stress: A Continuation Report.
- 2015
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Ingår i: Ultrasound in Medicine and Biology. - : Elsevier BV. - 0301-5629. ; 41:5, s. 1342-1353
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Tidskriftsartikel (refereegranskat)abstract
- The mechanisms underlying longitudinal displacements of the arterial wall, that is, displacements of the wall layers along the artery, and the resulting intramural shear strain remain largely unknown. We have already found that these displacements undergo profound changes in response to catecholamines. Wall shear stress, closely related to wall shear rate, represents the viscous drag exerted on the vessel wall by flowing blood. The aim of the work described here was to study possible relations between the wall shear rate and the longitudinal displacements. We investigated the carotid arteries of five anesthetized pigs in different hemodynamic situations using in-house developed non-invasive ultrasound techniques. The study protocol included administration of epinephrine, norepinephrine and β-blockade (metoprolol). No significant correlation between longitudinal displacement of the intima-media complex and wall shear rate was found. This result suggests that one or multiple pulsatile forces other than wall shear stress are also working along arteries, strongly influencing arterial wall behavior.
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| 6. |
- Segstedt, Simon, et al.
(författare)
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Arterial diameter change measurements in premature rabbit pups using B-Mode images
- 2012
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Ingår i: 2012 IEEE International Ultrasonics Symposium (IUS). ; , s. 922-924
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Konferensbidrag (refereegranskat)abstract
- To further promote cardiovascular research there is a growing need for arterial characterization on small animals. Arterial wall movement measurements form the basis for most stiffness related parameters. As far as we know, previous reports on lumen diameter change measurements in small animals have required ECG triggering and cross-correlation techniques on the RF-signal using extremely high frame rate. The first aim of this study was to evaluate a novel method, ARTerIal Characterization (ARTIC), for robust diameter measurements in premature rabbit pups using conventional scanning technique (B-mode, 230 Hz). Although blood pressure is important for arterial stiffness measurements, it is often impossible to obtain without affecting the animal setup. However, arterial stiffness can also be assessed by measuring the pressure independent transition strain as recently proposed by Danpinid et al. (Ultrasonics 50, 2010: 654-665). The second aim was to investigate the feasibility of measuring transition strain in premature rabbit pups using the obtained diameter curve. The diameter was 874/82 mu m (mean/SD), CV 2.9%. The distension was 24+/-3 mu m, CV 7.3%. The transition strain was 1.55+/-0.46%, CV 12.8%. In summary, ARTIC can measure arterial diameter and distension in small animals using B-Mode images at regular frame rates. ARTIC also has a low computation time suitable for real-time implementation. Measurements of transition strain on premature rabbit pups are feasible using B-Mode images at regular frame rate. (Abstract)
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