Shear wave elastography of the testes in a healthy study collective - Differences in standard values between ARFI and VTIQ techniques

Abstract

Introduction: Shear wave elastography (SWE) is a recent technique in the assessment of tissue elasticity. Different elastography techniques have been described over the years.Acoustic Radiation Force Impulse Imaging (ARFI) uses mechanical excitation of tissue to create detectable shear waves, a higher shear wave velocity being associated with an increased tissue stiffness.The Virtual Touch Tissue Imaging Quantification (VTIQ) method uses a mechanical push pulse as well, additionally creating a colour-coded map, in which tissue stiffness can be measured within a stored map on the ultrasound device after measurement.ARFI has been used in determining standard values in testes of a healthy study collective, VTIQ has already been used in the evaluation of unclear scrotal masses.Both techniques allow an operator-independent examination without application of mechanical pressure. The aim of this study was to determine whether there is a statistically significant difference between shear wave velocity values of both techniques in a healthy collective.

Material and methods: Twenty patients without known testicular pathology underwent standard B-mode sonography and additional shear wave elastography in the ARFI mode as well as the VTIQ technique of both testes using the Siemens Acuson S2000™ and S3000™ ultrasound devices (Siemens HealthCare, Erlangen, Germany).Measurements of shear wave velocity were performed in the upper pole, the central portion and the lower pole separately for each testis. Values were described in m/s.Statistical evaluation was performed using paired t-test analysis.

Results: We measured a mean shear wave velocity of 0.81 m/s using ARFI and 1.07 m/s with VTIQ.Shear wave velocities determined by VTIQ were all significantly higher than values gained in the ARFI mode. (p < 0.001 to p = 0.007). Values were between 0.22 and 0.29 m/s higher, when the examination was performed using VTIQ.

Conclusion: ARFI and VTIQ elastography modes both proved to be feasible techniques in the assessment of testicular tissue elasticity. Consideration of higher values for VTIQ is important, when different elastography measurement results are compared, especially for the application of devices in a clinical setting, e.g. in the work-up of scrotal masses.A calculable factor for a comparison between both devices is desirable, but to be further assessed in largerstudies.

Keywords: ARFI; Testis; VTIQ; shear wave elastography; ultrasonography.