| 1. |
- 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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| 2. |
- Erlöv, Tobias, et al.
(författare)
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A method for measuring the variation of intima-media thickness during the entire cardiac cycle using B-Mode images
- 2011
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Ingår i: 2011 IEEE International Ultrasonics Symposium (IUS). - 9781457712531 ; , s. 2126-2129
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Konferensbidrag (refereegranskat)abstract
- Increased intima-media thickness (IMT) has been shown to predict cardiovascular risk, and measurement of intima-media thickness has been extensively used in medical research since the mid-1990s. IMT is conventionally measured by manual tracing, however this method is very time-consuming and suffers from large inter-observer variability. Numerous methods, both semi-automatic and fully-automatic, have been suggested to limit the influence of the observer. However, most methods only report one value per cardiac cycle instead of the variation of IMT over time. We propose a new method that measures the variation of IMT during the entire cardiac cycle. The method tracks spatial variations with compensation for both longitudinal movement and angle variations. This enables detection of positions where an inaccurate measurement of IMT has occurred. These can then be removed from the calculations in order to maximize the accuracy. The method was evaluated in vivo on 20 healthy individuals (mean age 38 years, range 25-57). The overall IMT in diastole (IMTdia) was 717+/-69 mu m and the intima-media compression (IMC) was 66+/-21 mu m which corresponds to a 9.2+/-2.6% maximal compression of the arterial wall during a cardiac cycle. The CV was 3.5% for IMTdia and 9.9% for IMC. Extending traditional IMT measurement to include also the variation of IMT during a cardiac cycle may improve the individual risk classification for cardiovascular diseases.
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| 3. |
- Erlöv, Tobias, et al.
(författare)
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A Method to Measure Shear Strain with High Spatial Resolution in the Arterial Wall Non-Invasively in vivo by Tracking Zero-Crossings of B-Mode Intensity Gradients
- 2010
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Ingår i: Proceedings - IEEE Ultrasonics Symposium. - 9781457703812 ; , s. 491-494
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Konferensbidrag (refereegranskat)abstract
- We have previously shown that there is a distinct longitudinal movement of the arterial wall during a cardiac cycle. This movement is larger in the intima-media region than in the adventitial region which introduces a substantial shear strain within the arterial wall. Our previously developed echo-tracking algorithm measured this shear strain by tracking two separate echoes, one in the intima-media region and one in the adventitia region and thus only a linear distribution was evaluated. The objective of this study was to suggest and evaluate a new improved method which can measure the intramural shear strain with higher spatial resolution and thereby provide more information on this new and rather unknown phenomenon. The mean maximum shear strain was 0.82 radians with a standard deviation of 0.17 radians and a CV-value of 14.2%. The total mean difference in measured longitudinal movement between the new and previous method was 10μm with a standard deviation of 90μm and a CV-value of 12.8%. The spatial distribution of the intramural shear strain seems to be very non-linear with a large amount of shear strain occurring in a small section around the transition between the media and adventitia layers.
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