Lateral blood flow velocity estimation based on ultrasound speckle size change with scan velocity

• Published in: IEEE transactions on ultrasonics, ferroelectrics, and frequency control Vol. 57; no. 12; pp. 2695 - 2703
• Main Authors: Tiantian Xu, Bashford, G R
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01.12.2010; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Acoustical measurements and instrumentation; Acoustics; Biological and medical sciences; Biomedical imaging; Blood; Blood flow; Blood Flow Velocity; Cardiovascular system; Computer Simulation; Data models; Estimation; Exact sciences and technology; Flow velocity; Fluid dynamics; Fluid flow measurement; Fundamental areas of phenomenology (including applications); Instrumentation for fluid dynamics; Investigative techniques, diagnostic techniques (general aspects); Least-Squares Analysis; Medical sciences; Methods; Models, Biological; Phantoms; Phantoms, Imaging; Physics; Signal Processing, Computer-Assisted; Speckle; Ultrasonic investigative techniques; Ultrasonography - methods; Electronic control; Lateral lobe; Gradient; Pulse echo method; Probabilistic approach; Error estimation; Erythrocytes; Flow measurement; Doppler effect; Blood; Blood flow; Speckles; Blood circulation; Linear antennas; Flow velocity; Modelling; Circulatory system; Decorrelation; Man; Flowmetry; Least square fit; Blood flow measurement; A scan
• ISSN: 0885-3010; 1525-8955; 1525-8955
• DOI: 10.1109/TUFFC.2010.1743

Conventional (Doppler-based) blood flow velocity measurement methods using ultrasound are capable of resolving the axial component (i.e., that aligned with the ultrasound propagation direction) of the blood flow velocity vector. However, these methods are incapable of detecting blood flow in the direction normal to the ultrasound beam. In addition, these methods require repeated pulse-echo interrogation at the same spatial location. A new method has been introduced which estimates the lateral component of blood flow within a single image frame using the observation that the speckle pattern corresponding to blood reflectors (typically red blood cells) stretches (i.e., is smeared) if the blood is moving in the same direction as the electronically-controlled transducer line selection in a 2-D image. The situation is analogous to the observed distortion of a subject photographed with a moving camera. The results of previous research showed a linear relationship between the stretch factor (increase in lateral speckle size) and blood flow velocity. However, errors exist in the estimation when used to measure blood flow velocity. In this paper, the relationship between speckle size and blood flow velocity is investigated further with both simulated flow data and measurements from a blood flow phantom. It can be seen that: 1) when the blood flow velocity is much greater than the scan velocity (spatial rate of A-line acquisition), the velocity will be significantly underestimated because of speckle decorrelation caused by quick blood movement out of the ultrasound beam; 2) modeled flow gradients increase the average estimation error from a range between 1.4% and 4.4%, to a range between 4.4% and 6.8%; and 3) estimation performance in a blood flow phantom with both flow gradients and random motion of scatterers increases the average estimation error to between 6.1% and 7.8%. Initial attempts at a multiple-scan strategy for estimating flow by a least-squares model suggest the possibility of increased accuracy using multiple scan velocities.