Multisection two-dimensional survey acquisitions were obtained to localize the distal aorta and iliac arteries. An overview of the measurement scheme is given in Table 1.ДЄll participants underwent phase-contrast 3.0-T MRI (Ingenia Philips Healthcare) by using a phased-array torso coil within 1 month before or after echo PIV measurements. After this measurement, four incremental contrast agent doses were administered to each participant (0.25, 0.5, 0.75, and 1.5 mL) to investigate the optimal dose for PIV analysis. First, HFR measurement without contrast agent administration was performed. A stable concentration of contrast agent was used for starting the HFR CE US measurements, and subsequent injections were given only after substantial washout of the agent.ДЇor each measurement, images were captured for 2.5 seconds at 1000 frames per second using a three-angled diverging wave acquisition scheme. The Epiq 7 US machine was also used by a researcher (S.E.) for visual contrast monitoring in the left superficial femoral artery. Contrast agent was injected by a physician with experience in CE US examinations (P.T.). The Vantage 256 US machine was controlled by a researcher (J.V.). The aortic bifurcation was visualized in a coronal oblique view by an experienced vascular technologist. Before US, physical examination was performed and blood flow velocity in the distal abdominal aorta was measured with pulsed wave Doppler imaging by using an Epiq 7 US machine (Philips Healthcare, Best, the Netherlands).ДЄ four-member research team performed the echo PIV measurements. The objective of this study was to investigate the feasibility of echo PIV to visualize blood flow in the human abdominal aorta by using phase-contrast MRI as a reference.Д®cho PIV was performed with a fully programmable Vantage 256 US machine (Verasonics, Kirkland, Wash) with a curvilinear array abdominal probe (C5вЂ“2 ATL, Bothell, Wash). In vitro models at an imaging depth of 10 cm suggested the feasibility of abdominal echo PIV with HFR CE US ( 7). However, little is known about the amount of contrast agent required for optimal PIV analysis. In the abdominal aorta, US is complicated by loss of signal due to bowel gas or imaging depth, which could be compensated by using US contrast agents.

However, flow velocities of approximately 1 m/sec, which can be found in the human abdominal aorta, have not been successfully quantified until recently ( 6). Recent developments in the use of high-frame-rate (HFR) contrast materialвЂ“enhanced (CE) US have improved the possibilities of quantifying blood flow with echo PIV. With this technique, US images are acquired and used for PIV analysis. In the carotid artery and the heart, US particle image velocimetry (hereafter, echo PIV) has been used to obtain two-dimensional velocity vector fields of blood flow in the axial and lateral directions ( 4, 5). However, because the aortoiliac bifurcation is perpendicular to the transducer, it is difficult to obtain reliable flow quantification with Doppler imaging. Imaging of endovascular flow patterns in the abdominal aorta is challenging but clinically relevant because of the relationship between local hemodynamics and the development of vascular diseases ( 1вЂ“ 3).Д¬onventional Doppler US enables a one-dimensional blood flow velocity estimate in the axial direction.

Tecplot 360 velocity profile tutorial