Shear Wave Dispersion Ultrasound Vibrometry Based on a Different Mechanical Model for Soft Tissue Characterization

Abstract

he study of shear moduli has great potential for tissue characterization because the range of variation in the shear moduli is several orders more than that for the bulk moduli for various biological tissues. 1 An effective approach for noninvasively measuring the shear moduli is to quantify responses of the tissue stressed by external force. Three of the main challenges in obtaining the shear moduli of soft tissue are as follows: (1) remotely generating a shear wave with the frequencies of interest in a tissue region; (2) noninvasively measuring the propagation of the induced shear wave, which quickly attenuates over distances; and (3) selecting a tissue model and calculating the tissue shear moduli of the model using measured shear waves.Several research groups showed that it is feasible to remotely generate motions in a tissue region using ultrasound radiation force. Dual beams or amplitude modulations were used to induce harmonic motions with a prescribed frequency. 2 Pushing pulses were used to generate pulsed motions. 3 Periodic pushing pulses were used to generate harmonic motions with multiple prescribed frequencies. 4 The three classic models, Voigt, Maxwell, and Zener, were applied to fit the velocity measurements and estimate shear moduli of porcine livers with different thermal damage levels and different storage times. The Zener model always provided the best estimation of the moduli with the minimum errors in our experiments. Unlike the Voigt and Maxwell models, the moduli of the Zener model cannot be used to indicate damage levels in porcine livers directly, but the creep and relaxation behaviors of the Zener model are effective.

Analyzing and modeling rheological behavior of liver fibrosis in rats using shear viscoelastic moduli

“…For the Voigt model, the elasticity E is a constant in the frequency domain. As the Zener model describes creep and relaxation, while the Voigt model describes creep, the Zener model is equal to the Voigt model if (6) F1 (5) F2 (9) F3 (5) F4 ( Data are expressed as mean±standard deviation (SD) its elasticity E 2 is infinite (Chen et al, 2012 Our results are in agreement with the studies reported in the past. Asbach et al (2008) studied eight healthy volunteers and eight patients with biopsyproven liver fibrosis (grades 3-4) by magnetic resonance (MR) elastography.…”

Magnetomotive optical coherence elastography using magnetic particles to induce mechanical waves

“…6(c) where the estimated values of G = 1.7 kPa and η = 0.83 Pa·s are consistent with the values reported in previous studies [38]. However, in biological tissues, it is widely acknowledged that the inherent biological variability and the tissue preparation and storage methods can have a significant influence on the measured viscoelastic properties [45].…”

Assessment of liver fibrosis using fast strain‐encoded MRI driven by inherent cardiac motion

“…This is substantially lower than the reported SWV of 1.2 m/s using ARFI or FibroScan techniques with an external ultrasound pulsar . However, SWV depends on the frequency of the shear wave and declines substantially at pushing pulse frequencies below 200 Hz . ARFI and SDUV techniques use extremely short ultrasound pulses at frequencies in the KHz and MHz range and duration, whereas FibroScan uses a 50‐Hz pulser.…”