Artifacts and Technical Restrictions in 2D Shear Wave Elastography.

2 D shear wave elastography (2D-SWE) is the latest evolution of elastography techniques and allows real-time quantitative assessment of the medium stiffness. The aim of this review is to identify, describe, explain and illustrate some technical restrictions and artifacts in 2D-SWE. Encountered artifacts and technical restrictions may be categorized according to acquisition technique, medium, or operator: · Acquisition technique: B-mode & SWE entanglement, transducer frequency, posterior elastographic shadowing artifact, mirrored elastogram artifact, "vertical striped" artifact, resolution limits in SWE, non-equivalence of elastographic devices. · Medium: SWE in liquid medium, "black hole phenomenon", pseudo-liquid lesions, musculotendinous anisotropy, intrinsic stiffness variations of tendons and muscles, depth of analysis, movement artifacts. · Operator: Region of interest compression, acquisition and measurement parameters (ROI size, ROI location, elastogram acquisition time). Clear knowledge of the underlying physical basis is necessary in 2D-SWE because radiologists have to deal with technical restrictions and a wide range of artifacts. Proper use of 2D-SWE ensures the reliability and reproducibility of the technique.

Evaluation of the Effect of an Anisotropic Medium on Shear Wave Velocities of Intra-Muscular Gelatinous Inclusions.

In highly anisotropic biological tissues such as muscle or tendons, calculating Young's modulus from the shear wave speed (csw) by using shear wave elastography (SWE) involves a complex transversally isotropic rheological model not yet used in common practice. To our knowledge, the effect of muscle anisotropy on csw of intra-muscular lesions has not yet been investigated. The objective of our study was to define the effect of an anisotropic medium on csw of intra-muscular gelatinous inclusions. We conducted a prospective monocentric, in vitro study in order to examine the quantitative and qualitative SWE behavior of a 9-mm gelatinous intra-muscular implant depending on the orientation of the probe relative to the muscle fibers. There were very significant differences in the prevalence of SWE signal void (p < 0.01) and in the csw (p < 0.01) in the gelatinous intra-muscular implants depending on the orientation of the probe relative to the fibers. Performing the csw measurements of centimetric intra-muscular lesions by orienting the probe perpendicular to the fibers decreases the probability of artifacts occurring at high intensity interfaces.