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A new imaging method for assessment of aortic dissection using four-dimensional phase contrast magnetic resonance imaging Rachel E. Clough, MBBS, BSc, MRCS, Matthew Waltham, MA, PhD, FRCS, Daniel Giese, Dipl Phys, Peter R. Taylor, MA, MChir, FRCS, Tobias Schaeffter, PhD Journal of Vascular Surgery Volume 55, Issue 4, Pages (April 2012) DOI: /j.jvs Copyright © 2012 Society for Vascular Surgery Terms and Conditions
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Fig 1 Sagittal section through the aorta shows blood flow velocity at five time points in the cardiac cycle. Thrombus can be accurately delineated and is seen proximally in the false lumen. A, High velocity complex flow is seen in the vicinity of the entry tear. B, There is low flow (dark blue on the velocity indicator bar) in the region of the thrombus. Dynamic images demonstrate flow patterns that relate to the morphology of the thrombus (curved arrows). C, A further high velocity jet is seen in the true lumen as the dissection flap moves from posterior to anterior in early diastole (400 ms image). Journal of Vascular Surgery , DOI: ( /j.jvs ) Copyright © 2012 Society for Vascular Surgery Terms and Conditions
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Fig 2 Identification and quantification of helical flow. A, The entire aorta was inspected and areas of helical flow were identified. B, A plane was positioned perpendicular to the bulk direction of flow. C, Helicity (degrees/s) was quantified by assessment of the amount of rotation in the plane and the start and end time in the cardiac cycle. Journal of Vascular Surgery , DOI: ( /j.jvs ) Copyright © 2012 Society for Vascular Surgery Terms and Conditions
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Fig 3 Correlation analyses and Bland-Altman plots of two-dimensional (2D) and four-dimensional (4D) phase contrast magnetic resonance imaging (PC-MRI). Stroke volume calculated by 2D PC-MRI and 4D PC-MRI showed good agreement with no proportional bias. Asc Ao, Ascending aorta. Journal of Vascular Surgery , DOI: ( /j.jvs ) Copyright © 2012 Society for Vascular Surgery Terms and Conditions
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Fig 4 Box and whisker and line plots of stroke volume and velocity in the true and false lumen. The box plots give a graphic description of the differences between the groups, whereas the individual line plots show paired observations for each individual and demonstrate the variation between patients. The median stroke volume and blood flow velocity was greater in the true compared with the false lumen. There was significant variation in the flow characteristics between different patients, for example in two patients, the majority of the stroke volume was through the false rather than true lumen. The horizontal line in the middle of each box indicates the median; the top and bottom borders of the box mark the 75th and 25th percentiles, respectively; and the whiskers mark the maximum and minimum values. Journal of Vascular Surgery , DOI: ( /j.jvs ) Copyright © 2012 Society for Vascular Surgery Terms and Conditions
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Fig 5 Visualization of entry tears. Communications between the true and false lumen (entry tears) were identified using pathline analysis. These images can be viewed in 3D over time in any chosen orientation. A single plane has been selected for illustration and flow shown at five time points in the cardiac cycle. A, One entry tear is seen at the origin of the left subclavian artery. In systole (158 and 215 ms), the velocity in the true and false lumen is approximately equal. B, Blood flows from the true to the false lumen through an entry tear in the proximal descending thoracic aorta. An area of high velocity is seen just distal to the entry tear as the false lumen expands (because of the additional flow) and true lumen narrows. Flow is seen the celiac and superior mesenteric arteries (SMA) distally. Journal of Vascular Surgery , DOI: ( /j.jvs ) Copyright © 2012 Society for Vascular Surgery Terms and Conditions
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