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

Abstract

Being able to measure 3D flow velocity and volumetric flow rate effectively in the cardiovascular system is valuable but remains a significant challenge in both clinical practice and research. Currently there has not been an effective and practical solution to the measurement of volume flow using ultrasound imaging systems due to challenges in existing 3D imaging techniques and high system cost. In this study, a new technique for quantifying volumetric flow rate from the crosssectional imaging plane of the blood vessel was developed by using speckle decorrelation, 2D high frame rate imaging with a standard 1D array transducer, microbubble contrast agents, and ultrasound imaging velocimetry (UIV). Through speckle decorrelation analysis of microbubble signals acquired with a very high frame rate and by using UIV to estimate the two in-plane flow velocity components, the third and out-of-plane velocity component can be obtained over time and integrated to estimate volume flow. The proposed technique was evaluated on a wall-less flow phantom in both steady and pulsatile flow. UIV in the longitudinal direction was conducted as a reference. The influences of frame rate, mechanical index, orientation of imaging plane, and compounding on velocity estimation were also studied. In addition, an in vivo trial on the abdominal aorta of a rabbit was conducted. The results show that the new system can estimate volume flow with an averaged error of 3.65±2.37% at a flow rate of 360 ml/min and a peak velocity of 0.45 m/s, and an error of 5.03±2.73% at a flow rate of 723 ml/min and a peak velocity of 0.8 m/s. The accuracy of the flow velocity and volumetric flow rate estimation directly depend on the imaging frame rate. With a frame rate of 6000 Hz, a velocity up to 0.8 m/s can be correctly estimated. A higher mechanical index (MI=0.42) is shown to produce greater errors (up to 21.78±0.49%, compared to 3.65±2.37% at MI=0.19). An in vivo trial, where velocities up to 1 m/s were correctly measured, demonstrated the potential of the technique in clinical applications.

Determining Haemodynamic Wall Shear Stress in the Rabbit Aorta In Vivo Using Contrast-Enhanced Ultrasound Image Velocimetry

“…Future work should aim to derive WSS from fully 3D measurements of flow by acquiring 4D data, 5,31 by measuring multiple planes 37 or by using speckle decorrelation methods. 36 Despite its limitations we demonstrated that 2D UIV can be used to map TAWSS xz and OSI xz in the abdominal aorta of NZW rabbits. Hence 2D UIV can be used to study the formation and progression of cardiovascular disease.…”

Functional ultrasound speckle decorrelation-based velocimetry of the brain

“…Conventionally, ultrasound speckle is considered as undesirable noise that impacts ultrasound image contrast negatively and a main focus of research has been on the removal of ultrasound speckle 31 . Currently, two ultrasound speckle analysis methods have been studied trying to use ultrasound speckle to resolve flow information, including the cross correlation-based ultrasound imaging velocimetry (UIV) 14,15 and the B-mode intensity-based speckle decorrelation method (SDC) 16,17 . By exploiting dynamic analysis of the normalized first order field autocorrelation function ( 1 ( ) ) of the complex ultrasound quadrature signal, for the first time to the best of our knowledge, we developed the comprehensive vUS theory to accurately measure axial velocity and transverse velocity under different scenarios.…”

“…Here, we report a novel ultrasound speckle decorrelation-based velocimetry (vUS) method as a quantitative alterative to fUS and a faster velocimetry method than vULM. In contrast to speckle correlation-based ultrasound imaging velocimetry (UIV) 14,15 and Bmode intensity signal-based speckle decorrelation method (SDC) 16,17 , vUS measures the 'angle-independent' directional blood flow velocity by quantifying the decorrelation of the normalized first order temporal autocorrelation function ( 1 ( )) of the complex ultrasound quadrature signal (sIQ). We developed a comprehensive ultrasound-based 1 ( ) analysis theory and data processing methodology for cerebral blood flow velocity measurement.…”

Measurement of Flow Volume in the Presence of Reverse Flow with Ultrasound Speckle Decorrelation

“…Ultrasound speckle decorrelation (SDC) has shown the capability in estimating the through-plane flow velocity using a 1-D array transducer (Rubin et al, 2001, Park et al, 2013, Zhou et al, 2018). With the through-plane velocity, the flow volume can be calculated by integrating the velocity over the luminal area when the vessel is scanned in the transverse view.…”

“…Furthermore, the advent of microbubble contrast agents can also significantly enhance the ultrasound signal from blood. Using high frame rate imaging techniques and microbubbles contrast agents, we have recently demonstrated the feasibility of the SDC method both in vitro and in vivo , showing that the maximum measurable through-plane flow velocity can be well over 1 m/s, which is physiologically equivalent to most flow in the cardiovascular system (Zhou et al 2018). However, the current SDC method has an intrinsic limitation on differentiating the flow direction in the blood vessel.…”