| 1. |
- Ahlgren, Åsa Rydén, et al.
(författare)
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Response of the carotid artery longitudinal motion to submaximal physical activity in healthy humans-Marked changes already at low workload
- 2023
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Ingår i: Physiological Reports. - : Wiley. - 2051-817X. ; 11:2
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Tidskriftsartikel (refereegranskat)abstract
- The longitudinal motion of the arterial wall, that is, the displacement of the arterial wall along the artery, parallel to blood flow, is still largely unexplored. The magnitude and nature of putative changes in longitudinal motion of the arterial wall in response to physical activity in humans remain unknown. The aim of this study was therefore to study the longitudinal motion of the carotid artery wall during physical activity in healthy humans. Using in-house developed non-invasive ultrasonic methods, the longitudinal motion of the intima-media complex and the diameter changes of the right common carotid artery (CCA) in 40 healthy volunteers (20 volunteers aged 22-35 years; 20 volunteers aged 55-68 years) were assessed at rest and during submaximal supine bicycle exercise. In a subset of the subjects (n = 18) also intramural shear strain were analyzed. The longitudinal motion of the intima-media complex underwent marked changes in response to physical activity, already at low workload; with most evident a marked increase of the first antegrade displacement (p < 0.001) in early systole. Likewise, the corresponding shear strain also increased significantly (p = 0.004). The increase in longitudinal motion showed significant correlation to increase in blood pressure, but not to blood flow velocity or wall shear stress. In conclusion, physical activity markedly influences the longitudinal motion of the carotid artery wall in healthy humans already at low load. A possible "cushioning" function as well as possible implications for the function of the vasa vasorum, endothelium, and smooth muscle cells and extracellular matrix of the media, are discussed.
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| 2. |
- Albinsson, John, et al.
(författare)
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A combination of parabolic and grid slope interpolation for 2D tissue displacement estimations
- 2017
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Ingår i: Medical & Biological Engineering & Computing. - : Springer Science and Business Media LLC. - 0140-0118 .- 1741-0444. ; 55:8, s. 1327-1338
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Tidskriftsartikel (refereegranskat)abstract
- Parabolic sub-sample interpolation for 2D block-matching motion estimation is computationally efficient. However, it is well known that the parabolic interpolation gives a biased motion estimate for displacements greater than |y.2| samples (y = 0, 1, …). Grid slope sub-sample interpolation is less biased, but it shows large variability for displacements close to y.0. We therefore propose to combine these sub-sample methods into one method (GS15PI) using a threshold to determine when to use which method. The proposed method was evaluated on simulated, phantom, and in vivo ultrasound cine loops and was compared to three sub-sample interpolation methods. On average, GS15PI reduced the absolute sub-sample estimation errors in the simulated and phantom cine loops by 14, 8, and 24% compared to sub-sample interpolation of the image, parabolic sub-sample interpolation, and grid slope sub-sample interpolation, respectively. The limited in vivo evaluation of estimations of the longitudinal movement of the common carotid artery using parabolic and grid slope sub-sample interpolation and GS15PI resulted in coefficient of variation (CV) values of 6.9, 7.5, and 6.8%, respectively. The proposed method is computationally efficient and has low bias and variance. The method is another step toward a fast and reliable method for clinical investigations of longitudinal movement of the arterial wall.
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| 3. |
- Albinsson, John, et al.
(författare)
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Combined use of Iteration, Quadratic Interpolation and an Extra Kernel for high-resolution 2D particle tracking : a first evaluation
- 2010
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Ingår i: 2010 ieee international ultrasonics symposium. - New York : IEEE Press. - 9781457703829 ; , s. 2000-2003
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Konferensbidrag (refereegranskat)abstract
- A novel 2D particle tracking method, that uses 1) iteration, 2) fast quadratic sub-pixel estimation (with only 28 multiplications per movement), and 3) a previous kernel, has been evaluated and compared with a full-search block-matching method. The comparison with high-frequency ultrasound data (40 MHz) was conducted in silico and on phantoms, which comprised lateral, diagonal, and ellipsoidal movement patterns with speeds of 0–15 mm/s. The mean tracking error was reduced by 68% in silico and 71% for the phantom measurements. When only sub-pixel estimation was used, the decrease in the tracking error was 61% in silico and 57% for the phantom measurements. As well as decreasing the tracking error, the new method only used 70% of the computational time needed by the full-search block-matching method. With a fast method having good tracking ability for high-frequency ultrasound data, we now have a tool to better investigate tissue movements and its dynamic functionality.
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| 4. |
- Albinsson, John, et al.
(författare)
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Improved tracking performance of lagrangian block-matching methodologies using block expansion in the time domain : In silico, phantom and invivo evaluations
- 2014
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Ingår i: Ultrasound in Medicine and Biology. - : Elsevier. - 0301-5629 .- 1879-291X. ; 40:10, s. 2508-2520
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to evaluate tracking performance when an extra reference block is added to a basic block-matching method, where the two reference blocks originate from two consecutive ultrasound frames. The use of an extra reference block was evaluated for two putative benefits: (i) an increase in tracking performance while maintaining the size of the reference blocks, evaluated using in silico and phantom cine loops; (ii) a reduction in the size of the reference blocks while maintaining the tracking performance, evaluated using in vivo cine loops of the common carotid artery where the longitudinal movement of the wall was estimated. The results indicated that tracking accuracy improved (mean - 48%, p<0.005 [in silico]; mean - 43%, p<0.01 [phantom]), and there was a reduction in size of the reference blocks while maintaining tracking performance (mean - 19%, p<0.01 [in vivo]). This novel method will facilitate further exploration of the longitudinal movement of the arterial wall. (C) 2014 World Federation for Ultrasound in Medicine & Biology.
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| 5. |
- Bjarnegård, Niclas, et al.
(författare)
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Age affects proximal brachial artery stiffness : differential behaviour within the length of the brachial artery?
- 2003
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Ingår i: Ultrasound in Medicine and Biology. - 0301-5629. ; 29:8, s. 1115-1121
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Tidskriftsartikel (refereegranskat)abstract
- With increasing age, the diameter of central elastic arteries increases, whereas their distensibility decreases. The purpose of this study was to investigate the mechanical properties of the proximal brachial artery in relation to age and gender. Distensibility coefficient (DC), stiffness and compliance coefficient (CC) were calculated in 136 healthy males and females (range 9-82 y) using echo-tracking sonography. CC decreased with age in both genders, but CC was higher in males. Stiffness increased and DC decreased with age in an exponential manner, without any differences between genders. In conclusion, as in central elastic arteries, the distensibility of the proximal brachial artery decreases with age, in contrast to earlier reports on the muscular distal brachial artery. This may imply that the transition between elastic and muscular artery behavior is within the length of the brachial artery. In future studies using the brachial artery, the examination site needs to be defined.
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| 6. |
- Bjarnegård, Niclas, et al.
(författare)
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The effect of sympathetic stimulation on proximal brachial artery mechanics in humans : differential behaviour within the length of the brachial artery
- 2004
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Ingår i: Acta Physiologica Scandinavica. - 0001-6772 .- 1365-201X. ; 182:1, s. 21-27
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Tidskriftsartikel (refereegranskat)abstract
- Aims: The mechanical properties of arteries play a major role in the regulation of blood pressure and cardiac performance. The effect of sympathetic stimulation on the mechanical properties of the proximal brachial artery was analysed in 18 healthy volunteers, nine young (25 ± 2 years) and nine elderly (69 ± 2 years).Methods: A non-invasive ultrasonic echo-tracking system for measurement of systolic/diastolic variation of the proximal brachial artery diameter in combination with intra-arterial pressure measurements was used to determine wall mechanics. The pressure–diameter (P–D) relationship, distensibility coefficient (DC), compliance coefficient (CC) and stiffness(β) were obtained at rest and during sympathetic stimulation induced by lower body negative pressure (LBNP).Results: The peripheral vascular resistance increased by 100 and 72%, respectively in the young and elderly during LBNP (P < 0.001). Simultaneously, the mechanical properties of the proximal brachial artery remained unaltered, as estimated from both P–D relationship and stiffness in young (β-index rest: 5.2 ± 0.9, LBNP: 5.5 ± 1.3, NS) as well as elderly (β-index rest: 13.6 ± 4.6, LBNP: 16.1 ± 4.7, NS).Conclusions: LBNP-induced sympathetic activation does not change proximal brachial artery mechanics, in contrast to earlier reports on the muscular distal brachial artery. This may imply that the transition between elastic and muscular artery behaviour is within the length of the brachial artery, where the site of transition from elastic to muscular wall structure needs to be specified in future studies.
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| 7. |
- Cinthio, Magnus, et al.
(författare)
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A Method for Arterial Diameter Change Measurements Using Ultrasonic B-Mode Data.
- 2010
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Ingår i: Ultrasound in Medicine and Biology. - : Elsevier BV. - 0301-5629. ; 36:9, s. 1504-1512
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Tidskriftsartikel (refereegranskat)abstract
- Arterial diameter change is related to distending blood pressure and is used in estimation of arterial stiffness parameters. A common technique to track the arterial walls is by integration of wall velocities estimated by different methods using cross correlation or tissue Doppler. However, because of the high pulse repetition frequency and the need for separate pulsing sequences, the B-mode image quality is affected. We have previously developed a fast algorithm for direct measurement of lumen diameter using B-mode images. In this study we have improved the technique to be more robust and also implemented measurements of diameter change, maximum differential wall velocity and relative diameter change of the common carotid artery noninvasively in vivo. The influence of the lateral width of the region of interest (ROI; 1 pixel, 0.1 mm, 0.5 mm, 1 mm, 2.5 mm and 5 mm) was evaluated. Using the optimal lateral width (2.5 mm), the systematic and random differences between two consecutive measurements were 21 mum and 105 mum, respectively, for lumen diameter measurement; -7 mum and 39 mum, respectively, for lumen diameter change measurements; -0.2 mm/s and 0.9 mm/s, respectively, for maximum relative wall velocity; and -0.2 % and 0.8 %, respectively, for measurements of the relative diameter change. The coefficient of variation (CV) was 1.9%, 5.2%, 7.9% and 6.0%, respectively. The study indicates that the reproducibility is sufficient for in vivo studies when the width of the ROI is 1.0 mm or wider. (E-mail: magnus.cinthio@elmat.lth.se).
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| 8. |
- Cinthio, Magnus, et al.
(författare)
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A NEW NON-INVASIVE ULTRASONIC METHOD FOR MEASUREMENTS OF LONGITUDINAL LENGTH ALTERATION OF THE ARTERIAL WALL - FIRST IN VIVO TRIAL
- 2008
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Ingår i: Acoustical Imaging. - 0270-5117. ; 29, s. 39-43
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Konferensbidrag (refereegranskat)abstract
- We have recently shown that there is a previous unknown longitudinal movement present in the arterial wall. We aim now to investigate whether the longitudinal movement causes length alteration of the arterial wall. The objective of this paper was to describe a new non-invasive ultrasonic technique that measures the length alteration of arteries in human in-vivo. Results indicate that a significant length alteration is present in the common carotid artery.
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| 9. |
- Cinthio, Magnus, et al.
(författare)
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An automatic method for measurements of arterial intima-media thickness using ultrasonic B-mode data
- 2012
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Ingår i: Acoustical Imaging. - Dordrecht : Springer Netherlands. - 9789400726185 - 9789400726192 ; 31, s. 115-122
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- We have previously developed algorithms that use B-mode cineloops for simultaneous measurements of arterial diameter change and longitudinal movement of the arterial wall. In this study the lumen diameter algorithm was extended to also measure arterial intima-media thickness of the far wall. To optimize the algorithm the influence of the lateral width of the region-of-interest (1 pixel, 0.1 mm, 0.5 mm, 1 mm, 2.5 mm and 5 mm) was evaluated. The algorithm estimated intima-media thickness at diastole automatically by measuring the distance between the two positions where the laterally averaged B-mode intensity envelope crosses a threshold value relative to the maximum amplitudes of the intimal and adventitial echoes, respectively. The sub-pixel resolution is achieved by solving the equation of a straight line between the two samples on either side of the threshold value. The measurements were performed on 20 healthy normotensive volunteers (age 25–57 years) on the common carotid artery 2–3 cm proximal to the bifurcation. For the 2.5-mm width, which was considered the best, the intima-media thickness was mean 646 μm (SD 66) for men and 613 μm (SD 68) for women. The systematic difference was −5 μm and the random difference was 31 μm. The CV was 4.9%. The study indicates that the reproducibility is sufficient for in vivo studies when the width of the region-of-interest is 1.0 mm or wider.
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| 10. |
- Cinthio, Magnus, et al.
(författare)
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Evaluation of an algorithm for arterial lumen diameter measurements by means of ultrasound.
- 2010
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Ingår i: Medical & Biological Engineering & Computing. - : Springer Science and Business Media LLC. - 0140-0118 .- 1741-0444. ; 48, s. 1133-1140
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Tidskriftsartikel (refereegranskat)abstract
- We have developed an algorithm for arterial luminal diameter measurement by means of ultrasound and evaluated the algorithm on agar vessel phantoms and in vivo. The algorithm utilises relative threshold detection on the inner slopes of the arterial walls before the resolution is improved by solving the equation of a straight line between the samples around the threshold value. Further, correction distances added to compensate for the underestimation when using the inner slopes were found to be 304 mum for the near wall and 415 mum for the far wall. The measured mean diameters of ten consecutive images of 3-, 6- and 9-mm phantoms were 3,006 mum (SD 4), 5,918 mum (SD 1) and 8,936 mum (SD 2), respectively. The mean differences between the images were 0.19, 0.04 and 0.37 mum, respectively. In vivo, the intra- and inter-observer variabilities were -64 mum (2SD 358) and -57 mum (2SD 366), respectively.
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