Quantification of Ultrasound Correlation‐Based Flow Velocity Mapping and Edge Velocity Gradient Measurement

Abstract

he blood flow velocity profile is important for diagnosis of cardiovascular diseases, which are associated with abnormal blood flow in arteries due to hemodynamic changes in patients. 1 The blood flow velocity gradient at the wall edge has been used to estimate the vascular wall shear stress, which has a key role in vascular physiology as well as the pathophysiologic mechanisms of vascular diseases. 2 Based on Poiseuille theory, the blood flow velocity profile is parabolic, and high-velocity gradients occur at the vascular wall in steady-state and fully developed laminar flow in normal conduit vessels. 3 In areas with vascular tortuosity, branching, and the presence of vascular plaque, the blood flow velocity profile is asymmetric. 1 Ultrasound imaging has been the preferred noninvasive technique for measuring blood flow velocity profiles.Multigate Doppler ultrasound measurement has been applied to estimate the blood flow velocity in vessels. 4 Using multigate Doppler measurements, the blood flow velocity profile and blood flow velocity gradient at the wall edge were determined from longitudinal (along the blood flow directions) views of blood vessels. [5][6][7][8] Dae Woo Park, PhD, Grant H. Kruger, PhD, Jonathan M. Rubin, MD, PhD, James Hamilton, PhD, Paul Gottschalk, PhD, Robert E. Dodde, PhD, Albert J. Shih, PhD, William F. Weitzel, MD Received January 1, 2013, This study investigated the use of ultrasound speckle decorrelation-and correlationbased lateral speckle-tracking methods for transverse and longitudinal blood velocity profile measurement, respectively. By studying the blood velocity gradient at the vessel wall, vascular wall shear stress, which is important in vascular physiology as well as the pathophysiologic mechanisms of vascular diseases, can be obtained. Decorrelationbased blood velocity profile measurement transverse to the flow direction is a novel approach, which provides advantages for vascular wall shear stress measurement over longitudinal blood velocity measurement methods. Blood flow velocity profiles are obtained from measurements of frame-to-frame decorrelation. In this research, both decorrelation and lateral speckle-tracking flow estimation methods were compared with Poiseuille theory over physiologic flows ranging from 50 to 1000 mm/s. The decorrelation flow velocity measurement method demonstrated more accurate prediction of the flow velocity gradient at the wall edge than the correlation-based lateral speckle-tracking method. The novelty of this study is that speckle decorrelation-based flow velocity measurements determine the blood velocity across a vessel. In addition, speckle decorrelation-based flow velocity measurements have higher axial spatial resolution than Doppler ultrasound measurements to enable more accurate measurement of blood velocity near a vessel wall and determine the physiologically important wall shear.

3-D Velocity and Volume Flow Measurement $In~Vivo$ Using Speckle Decorrelation and 2-D High-Frame-Rate Contrast-Enhanced Ultrasound

“…Values of BCW ranged between approximately 200 and 500 µm and increased linearly with depth even though the L12-3 probe has an elevational focal at 20 mm. Similar calibrated BCW curves have been found in other studies [21], [34]. When the depth is over 35 mm, the calibrated BCW values start to fluctuate, which is caused by the low signal-to-noise ratio (SNR) in the deeper area and the incoherence of the beam [34].…”

“…This study is the first to address that challenge by combining speckle decorrelation, 2D high-frame-rate plane wave ultrasound and microbubble contrast agents. Experiments in the flow phantom and the in vivo study of a rabbit aorta show not only that the new approach can accurately estimate flow but also that it substantially extends the upper limit of the measurable flow velocity, to above 1 m/s, compared to the 0.2 m/s obtained in previous studies that employed speckle decorrelation with conventional ultrasound techniques [21]. Such capability enables the technique to be used for measuring physiological flows in arteries.…”

“…The acoustic beam generated by the imaging system has a thickness in the elevational direction, and this allows the estimation of motion parallel to the vessel axis if the transducer is positioned to have a transverse view, as this motion will cause speckle decorrelation in the images. Although there have been many studies of speckle decorrelation (SDC) methods for 3D ultrasound imaging [13], [14], blood flow estimation [15]- [18] and the investigation of elastic tissue properties [19], [20], only a few of them focused on estimating the flow velocity or flow rate in the out-of-plane direction [17], [21], [22]. Furthermore, previous speckle decorrelation studies used only conventional, focused ultrasound; consequently, the maximum measurable velocity can only be about 0.2 m/s, which is more than an order of magnitude lower than peak physiological velocities in the cardiovascular system [21].…”

An FPGA-Based Backend System for Intravascular Photoacoustic and Ultrasound Imaging

“…Doppler and correlation-based velocity measurement cannot be used in side-looking imaging systems because the imaging plane is perpendicular to the blood flow. The decorrelation-based approach [6] can be used to measure blood velocity, but this approach requires extra calibration [25], which is difficult to perform in vivo . To enable forward-viewing capability and velocity measurement as well as to boost the frame rate of a combined IVPA and IVUS imaging system, a forward-looking transducer array can be used.…”

Quantitative technique for robust and noise-tolerant speed measurements based on speckle decorrelation in optical coherence tomography

“…Considering the literature on ultrasound speckle decorrelation for flow speed measurements in medical applications, it has been found that velocity estimations are strongly dependent on the noise of the data [25,26], a point that has not been addressed in speckle OCT systematically. Interestingly, we are aware of only a recent study that approaches the issue of a thorough validation of ultrasound speckle decorrelation measurements [27].…”