Validation of SMURF Estimation of Shear Modulus in Hydrogels

Abstract

A val i da tion study of the Spa tially Mod u lated Ul tra sound Ra di a tion Force (SMURF) method for shear modulus es ti ma tion is pre sented. SMURF es ti mates of uni form gel a tin and Zerdine™ phan toms cov er ing a modulus range of 2 to 18 kPa are com pared with re sults ob tained by un con fined me chan i cal com pres sion and sonoelastography. The re sults show agree ment within the mea sure ment un cer tain ties over the range in di cated for all three meth ods. Re peat abil ity and vari a tion on the or der of 5% of the phantom modulus are found for ob ser va tions made at a sin gle point within the phan tom. Av er ag ing of modulus es ti mates from sev eral ad ja cent scan lines fur ther de creases the vari a tion. By us ing mul ti ple radi a tion force peaks to in duce a shear wave of known wave length and mea sure the fre quency of the wave, SMURF ob tains modulus es ti mates from track ing data ac quired along a sin gle A-line. This is sig nif icant, as speckle can bias the mea sured phase of the shear wave. SMURF is shown to be in sen si tive to a con stant phase er ror in the shear wave mea sure ment. This re sults in greatly re duced cor re lated noise in the modulus es ti mates, in con trast with meth ods which track at mul ti ple lo ca tions and do not can cel phase er rors.

Shear Wave Velocity Imaging Using Transient Electrode Perturbation: Phantom and ex vivo Validation

“…Spatially-modulated acoustic radiation force (SMURF) imaging, an offshoot of ARFI, applies an acoustic pulse of known spatial frequency and measures the resulting temporal frequency of the shear wave. This technique has been used to estimate the shear modulus in gelatin phantoms [27], [28]. Radiation force perturbation methods benefit from precise positioning of the perturbation: either by moving the transducer or changing the acoustic pulse location on the face of the transducer.…”

Measurement of Liver Stiffness Using Shear Wave Elastography in a Rat Model: Factors Impacting Stiffness Measurement with Multiple- and Single-Tracking-Location Techniques

“…Single Tracking Location (STL)-Shear Wave Elasticity Imaging (SWEI) is a technique for estimating the shear stiffness of materials using Acoustic Radiation Force (ARF) to generate shear waves that are tracked using pulse-echo imaging along a single tracking location (McAleavey et al, 2007, 2009). The utility of STL-SWEI in the setting of liver fibrosis in a rat model is unclear.…”

Feasibility of using a generalized-Gaussian Markov random field prior for Bayesian speckle tracking of small displacements

“…ARF-based techniques include acoustic radiation force impulse (ARFI) imaging [1], shear-wave elasticity imaging (SWEI) [2], spatiallymodulated ultrasound radiation force (SMURF) [3], [4], and shear-wave dispersion ultrasound vibrometry (SDUV) [5]. Typically, these approaches displace tissue using long-duration excitation pulses and then measure the ARF-induced displacement between a pre-excitation pulse and tracking pulses acquired after the excitation.…”

“…Loupas's algorithmn [6]) tracking estimator to estimate ARF-induced displacements. However, thermal noise, shearing-induced decorrelation [7], [8], speckle-induced bias [3], [4], and finite tracking kernel-lengths, bandwidth, and sampling-rates [9] can limit the accuracy of the estimate.…”