A review of physical and engineering factors potentially affecting shear wave elastography

Abstract

It has been recognized that tissue stiffness provides useful diagnostic information, as with palpation as a screening for diseases such as cancer. In recent years, shear wave elastography (SWE), a technique for evaluating and imaging tissue elasticity quantitatively and objectively in diagnostic imaging, has been put into practical use, and the amount of clinical knowledge about SWE has increased. In addition, some guidelines and review papers regarding technology and clinical applications have been published, and the status as a diagnostic technology is in the process of being established. However, there are still unclear points about the interpretation of shear wave speed (SWS) and converted elastic modulus in SWE. To clarify these, it is important to investigate the factors that affect the SWS and elastic modulus. Therefore, physical and engineering factors that potentially affect the SWS and elastic modulus are discussed in this review paper, based on the principles of SWE and a literature review. The physical factors include the propagation properties of shear waves, mechanical properties (viscoelasticity, nonlinearity, and anisotropy), and size and shape of target tissues. The engineering factors include the region of interest depth and signal processing. The aim of this review paper is not to provide an answer to the interpretation of SWS. It is to provide information for readers to formulate and verify the hypothesis for the interpretation. Therefore, methods to verify the hypothesis for the interpretation are also reviewed. Finally, studies on the safety of SWE are discussed.

Preliminary study on cartilage tissue evaluation based on longitudinal and shear wave speeds

“…Although various methods for measuring the SWS have been proposed, [36][37][38][39] in this study, we measured the SWS using the TOF method based on linear regression. 33,39) The method for measuring the SWS is shown in Fig.…”

Advances in mechanical biomarkers

“…Combination of both ultrasound and magnetic elastography imaging techniques has shown significant improvements in the diagnosis 329 . Resolution limitations are still an issue in the application of elastography techniques and novel mathematical models are needed to interpret the complex dataset obtained 330 …”

“…329 Resolution limitations are still an issue in the application of elastography techniques and novel mathematical models are needed to interpret the complex dataset obtained. 330 Mechanical indentation by means of AFM and indenters has proven to be a reliable technique to obtain cancer mechanical biomarkers by several research works, 120,121 and companies like Artidis are developing mechanical indentation technology based on AFM of cancer biopsies for precision clinical diagnostic 51,331 (Figure 5F). ARTI-DIS ® uses tumoral biopsies extracted routinely in patients where a mass has been detected through imaging techniques and performs indentation measurements to detect possible mechanical biomarkers.…”

Combined ARFI and Shear Wave Imaging of Prostate Cancer: Optimizing Beam Sequences and Parameter Reconstruction Approaches

“…These artifacts can cause inaccurate shear wave speed estimates. 16 Multidimensional directional filters reduce reflection artifacts by attenuating shear waves traveling in the reflected direction. 17,18 Because the directional filter is applied in the Fourier domain, shear wave data that are spatially undersampled can lead to aliasing effects and reductions in filter efficacy.…”