Ultrasound elastography (USE) is a recent technology that has experienced major developments in the past two decades. The assessment of the main mechanical properties of tissues can be made with this technology by characterisation of their response to stress. This article reviews the two major techniques used in musculoskeletal elastography, compression elastography (CE) and shear-wave elastography (SWE), and evaluates the studies published on major electronic databases that use both techniques in the context of tendon pathology. CE accounts for more studies than SWE. The mechanical properties of tendons, particularly their stiffness, may be altered in the presence of tendon injury. CE and SWE have already been used for the assessment of Achilles tendons, patellar tendon, quadriceps tendon, epicondylar tendons and rotator cuff tendons and muscles. Achilles tendinopathy is the most studied tendon injury with USE, including the postoperative period after surgical repair of Achilles rupture tendon. In relation to conventional ultrasound (US), USE potentially increases the sensitivity and diagnostic accuracy in tendinopathy, and can detect pathological changes before they are visible in conventional US imaging. Several technical limitations are recognised, and standardisation is necessary to ensure repeatability and comparability of the results when using these techniques. Still, USE is a promising technique under development and may be used not only to promote an early diagnosis, but also to identify the risk of injury and to support the evaluation of rehabilitation interventions. • USE is used for the assessment of the mechanical properties of tissues, including the tendons. • USE increases diagnostic performance when coupled to conventional US imaging modalities. • USE will be useful in early diagnosis, tracking outcomes and monitoring treatments of tendon injury. • Technical issues and lack of standardisation limits USE use in the assessment of tendon injury.

/pdf/ultrasound-elastography-compression-elastography-and-shear-155dppxw1m.pdf

Ultrasound elastography: compression elastography and shear-wave elastography in the assessment of tendon injury.

Ultrasound is one of the workhorses in clinical cancer diagnosis. In particular, it is routinely used to characterize lesions inliver, urogenital tract, head and neck and soft tissues. During the last years image quality steadily improved, which, among others, can beattributed to the development of harmonic image analysis. Microbubbles were introduced as intravascular contrast agents and can be detectedwith superb sensitivity and specificity using contrast specific imaging modes. By aid of these unspecific contrast agents tissues canbe characterised regarding their vascularity. Antibodies, peptides and other targeting moieties were bound to microbubbles to target sitesof angiogenesis and inflammation intending to get more disease-specific information. Indeed, many preclinical studies proved the highpotential of targeted ultrasound imaging to better characterize tumors and to more sensitively monitor therapy response. Recently, firsttargeted microbubbles had been developed that meet the pharmacological demands of a clinical contrast agent.This review articles gives an overview on the history and current status of targeted ultrasound imaging of cancer. Different imaging conceptsand contrast agent designs are introduced ranging from the use of experimental nanodroplets to agents undergoing clinical evaluation.Although it is clear that targeted ultrasound imaging works reliably, its broad acceptance is hindered by the user dependency of ultrasoundimaging in general. Automated 3D-scanning techniques – like being used for breast diagnosis - and novel 3D transducers willhelp to make this fascinating method clinical reality.

Targeted Ultrasound Imaging of Cancer: An Emerging Technology on its Way to Clinics

Nonlinear characterization of breast cancer using multi-compression 3D ultrasound elastography in vivo.

The elastic properties of engineered biomaterials and tissues impact their post-implantation repair potential and structural integrity, and are critical to help regulate cell fate and gene expression. The measurement of properties (e.g., stiffness or shear modulus) can be attained using elastography, which exploits noninvasive imaging modalities to provide functional information of a material indicative of the regeneration state. In this review, we outline the current leading elastography methodologies available to characterize the properties of biomaterials and tissues suitable for repair and mechanobiology research. We describe methods utilizing magnetic resonance, ultrasound, and optical coherent elastography, highlighting their potential for longitudinal monitoring of implanted materials in vivo, in addition to spatiotemporal limits of each method for probing changes in cell-laden constructs. Micro-elastography methods now allow acquisitions at length scales approaching 5-100 μm in two and three dimensions. Many of the methods introduced in this review are therefore capable of longitudinal monitoring in biomaterials and tissues approaching the cellular scale. However, critical factors such as anisotropy, heterogeneity and viscoelasity-inherent in many soft tissues-are often not fully described and therefore require further advancements and future developments.

Application of Elastography for the Noninvasive Assessment of Biomechanics in Engineered Biomaterials and Tissues

The specific purpose of this review is to describe the progress of our work on elastography at the University of Texas Medical School-Houston in the past decade (2000-2010), and to relate it to our earlier work on this topic in the pre- ceding decade (1991-2000). This review is neither intended to cover all specific aspects of this fast growing field, nor to be an exhaustive review of the literature. Such information is available separately and in several literary reviews. The early work in our Laboratory was started (1) with the fundamental theoretical and experimental development of elas- tography and ended with demonstration of the feasibility of producing elastograms in a clinical setting (2). During the fol- lowing decade our work has branched out into three main directions. These were (1) a continued effort to demonstrate the ability of elastography to depict the elastic properties of tissues and to develop improved algorithms for attaining quality strain estimations; (2) the development and practical in vivo demonstration of Poisson's ratio elastography (poroelastogra- phy) for the study of poroelastic materials such as lymphedematous tissues; and (3) the development of axial-shear strain elastography (ASSE) for imaging the mechanical boundary conditions at tissue interfaces, and to demonstrate the utility of this modality in the differentiation between benign and malignant breast lesions in vivo. These three areas are the main topics that are covered in this review.

Elastography: A decade of progress (2000-2010)

The purpose of this work was to investigate the potential of the normalized axial-shear strain area (NASSA) feature, derived from axial-shear strain elastograms (ASSE), for breast lesion classification of fibroadenoma and cancer. This study consisted of previously acquired in vivo digital radiofrequency data of breast lesions. A total of 33 biopsy-proven malignant tumors and 30 fibroadenoma cases were included in the study, which involved three observers blinded to the original BIRADS-ultrasound scores. The observers outlined the lesions on the sonograms. The ASSEs were segmented and color-overlaid on the sonograms, and the NASSA feature from the ASSE was computed semi-automatically. Receiver operating characteristic (ROC) curves were then generated and the area under the curve (AUC) was calculated for each observer performance. A logistic regression classifier was built to compare the improvement in the AUC when using BIRADS scores plus NASSA values as opposed to BIRADS scores alone. BIRADS score ROC had an AUC of 0.89 (95% CI = 0.81 to 0.97). In comparison, the average of the AUC for all the three observers using ASSE feature alone was 0.84. However, the AUC increased to 0.94 (average of 3 observers) when BIRADS score and ASSE feature were combined. The results demonstrate that the NASSA feature derived from ASSE has the potential to improve BIRADS breast lesion classification of fibroadenoma and malignant tumors.

/pdf/axial-shear-strain-elastography-for-breast-lesion-d2zs5yhsxw.pdf

Srinivasa Chekuri

Papers

Axial-shear strain elastography for breast lesion classification: further results from in vivo data