Abstract
Shear wave elastography (SWE) induces lateral shear wave through acoustic pulses of the transducer and evaluates tissue stiffness quantitatively. This study was performed to evaluate feasibility and reproducibility of two-dimensional shear wave elastography (2D SWE) for evaluation of tissue stiffness and to examine technical factors that affect shear wave speed (SWS) measurements in adult dogs. Nine healthy, 2 year-old, adult beagles with the median weight of 9.8 kg were included. In this prospective, experimental, exploratory study, 2D SWE (Aplio 600) from the liver, spleen, kidneys, pancreas, prostate, lymph nodes (submandibular, retropharyngeal, axillary, medial iliac, and inguinal), submandibular salivary gland, and thyroid was performed in anesthetized beagles. Color map was drawn and SWS of each SWE were measured as Young’s modulus (kPa) and shear wave velocity (m/s). The effect of measuring site, scan approach, depth, and anesthesia on SWE was assessed in abdominal organs by two observers independently. A total of 27 SWE examinations were performed in 12 organs by each observer. All SWS measurements were preformed successfully; however, SWE in the renal medulla could not be successfully conducted, and it was excluded from further analysis. Interobserver agreement of SWE was moderate to excellent in all organs, except for the left liver lobe at 10–15 mm depth with the intercostal scan. In the liver, there was no significant effect of the measuring site and scan approach on SWE. SWS of the liver and spleen tended to be higher with increasing the depth, but no significant difference. However, anesthesia significantly increased tissue stiffness in the spleen compared to awake dog regardless of the depth (P < 0.05). There was a significant difference in SWS according to the measuring site in the kidneys and pancreas (P < 0.001). 2D SWE was feasible and highly reproducible for the estimation of tissue stiffness in dogs. Measuring site and anesthesia are sources of variability affecting SWE in abdominal organs. Therefore, these factors should be considered during SWS measurement in 2D SWE. This study provides basic data for further studies on 2D SWE on pathological conditions that may increase tissue stiffness in dogs.
Highlights
Stiffness indicates tissue resistance to deformation and can be expressed as deformability, which is the degree of deformation when a force is applied to the tissue (Shiina et al, 2015)
Two-dimensional shear wave elastography was feasible for acquisition of elastographic images and reliable shear wave speed (SWS) values from canine soft tissue organs. 2D Shear wave elastography (SWE) was performed with excellent interobserver agreement among 25 measurements in 12 organs
Evaluation of stiffness in abdominal organs, lymph nodes, submandibular gland and thyroid was feasible with 2D SWE, in anesthetized dogs with high reproducibility
Summary
Stiffness indicates tissue resistance to deformation and can be expressed as deformability, which is the degree of deformation when a force is applied to the tissue (Shiina et al, 2015). Shear wave elastography (SWE) induces lateral shear wave through acoustic pulses of the transducer and evaluates tissue stiffness quantitatively with shear wave speed (SWS; Shiina et al, 2015; Sigrist et al, 2017). In pSWE, the transducer generates a focal single acoustic pulse to induce displacement of tissue within a fixed region of interest (ROI; Cosgrove et al, 2013; Shiina et al, 2015; Sigrist et al, 2017). The operator chooses the location of ROI for pSWE as the uniform area of the parenchyma, the generated shear wave is not visualized itself and ROI size is usually small and fixed (Cosgrove et al, 2013; Sigrist et al, 2017)
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