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.

Multi-modal imaging of the subscapularis muscle.

The subscapularis (SSC) muscle is the most powerful of the rotator cuff muscles, and plays an important role in shoulder motion and stabilization. SSC tendon tear is quite uncommon, compared to the supraspinatus (SSP) tendon, and, most of the time, part of a large rupture of the rotator cuff. Various complementary imaging techniques can be used to obtain an accurate diagnosis of SSC tendon lesions, as well as their extension and muscular impact. Pre-operative diagnosis by imaging is a key issue, since a lesion of the SSC tendon impacts on treatment, surgical approach, and post-operative functional prognosis of rotator cuff injuries. Radiologists should be aware of the SSC anatomy, variability in radiological presentation of muscle or tendon injury, and particular mechanisms that may lead to a SSC injury, such as coracoid impingement. TEACHING POINTS: • Isolated subscapularis (SSC) tendon tears are uncommon. • Classically, partial thickness SSC tendon tears start superomedially and progress inferolaterally. • Long head of biceps tendon medial dislocation can indirectly signify SSC tendon tears. • SSC tendon injury is associated with anterior shoulder instability. • Dynamic ultrasound study of the SSC helps to diagnose coracoid impingement.