Comparison Between Strain and 2D Shear Wave Elastography of Testes in Healthy Dogs

Abstract

Sonoelastography is a rapid and non-invasive ultrasound-based technique to assess tissue elasticity. Interest in this technique's application in veterinary medicine is progressively increasing, with preliminary reports also available to assess canine testicular parenchyma abnormalities. Since elastographic techniques are different and it is of paramount importance to standardize procedures, this work aimed to compare two different elastographic techniques, SE and 2D SWE, on the same testes and compare the data with the current literature. Thirty healthy canine testes were included, and complete B-mode, color and power Doppler examinations were performed on each one. SE was performed qualitatively through an elastogram evaluation and semiquantitatively comparing the parenchyma with peripheral skin. 2D SWE was performed and m/s measurements were taken. Each measurement was collected in the cranial, middle and caudal portions, considering the sections above and below the mediastinum separately. The healthy testes appeared to be intermediate in stiffness with differences in the various portions for SE and expressed a mean value from 1.3 m/s to 1.4 m/s for 2D SWE, consistent with the previous literature. Considering the technical specifics of the software for the two elastography methods, both of them are valuable in assessing canine testis stiffness and are potentially clinically appliable.

Keywords: dog; shear wave elastography; strain elastography; testis; ultrasound.

Figure 1

Example of B-mode and color Doppler examination. In panels (A,B), respectively, longitudinal and transverse testicle sections are reported; note the medium level of ecogenicity with a homogeneous, medium–coarse echostructure and smooth margins. In panels (C,D), respectively, color and power Doppler on a longitudinal testicular section are reported, with normal parenchymal and epididymal vascularization.

Figure 2

Example of strain elastographic image of a testis on the longitudinal section. The dual-mode, real-time, biplane elasto-mode shows the B-mode image on the left side (panel (A)) and elastographic image on the right side (panel (B)); the testis shows a predominantly green/blue pattern (type III). The acquired appropriate compression force and frequency of elastography are monitored using a color scale, with green color indicating the correct compression applied (white arrow).

Figure 3

Example of testicular strain ratio measurement and evaluation. The light blue circle points to the examined testicular tissue (target tissue), with the yellow circle pointing to the skin considered as reference tissue. The result of this analysis is pointed out by the value within the white circle; values lower than 1 mean that the target tissue is softer than the reference one.

Figure 4

Example of 2D SWE examination of a testis on the longitudinal section. The B-mode longitudinal image of the normal testis is shown (A); the same image is visible with the superimposition of elastogram (B), whose colors are codified by the color bar present on the left side of the image. The elastogram appears homogeneously red, which states that the structure has low stiffness according to the color bar provided by the system. The circular ROI indicates where shear wave values expressed in m/s and kPa were measured, with results pointed out in panel (A).