Shear Wave Elastography: Comparing the Accuracy of Ultrasound Scanners Using Calibrated Phantoms in Experiment

Abstract

The aim of the study was to compare the accuracy of shear wave elastography performed by ultrasonic scanners from different manufacturers and to develop the conversion coefficients to recalculate the stiffness values obtained with different instruments using a calibrated phantom. Materials and Methods. A comparative analysis of the accuracy of stiffness measurements by shear wave point elastography was performed using three commercial ultrasonic scanners: Aixplorer (Supersonic Imagine, France), Acuson S2000 (Siemens, Germany), LOGIQ E9 (GE, USA), and the acoustic system Verasonics (Verasonics Inc., USA). The measurements were carried out using the calibrated phantom CIRS Model 049 Elasticity QA Phantom Spherical (Computerized Imaging Reference Systems Company, USA) that contained spherical inclusions of different stiffness. Results. With all tested scanners, comparable stiffness values with deviations within the measurement error were obtained. For the less stiff spheres of type I and type II, the obtained values were consistent with to the phantom calibration. For the medium-stiff phantom matrix, the measured values were at the lower limit of the calibration range. With the stiff spheres of type III, we found values lower than those predicted by calibration; the deviation was less pronounced in the linear sensor of the LOGIQ E9 scanner. In all sensors, this discrepancy increased along with increasing stiffness of the object. We developed formulas for recalculating the stiffness values for all tested scanners grouped by pairs. For example, for the pair of linear sensors Acuson S2000-Aixplorer, the conversion formulas of the Young's modulus E and the shear wave velocity V are as follows: E(Aixplorer, kPa)=3.11•V 2.06 (Acuson S2000, m/s) and V(Acuson S2000, m/s)=0.58•E 0.48 (Aixplorer, kPa). Conclusion. All tested sensors and scanners have a comparable high accuracy of shear wave point elastography. The tested instruments are more accurate when measuring objects with low stiffness; as the stiffness increases, the deviations from the standard values become greater. The formulas proposed for recalculating the stiffness indices allow an accurate comparison between the shear wave elastography results obtained with different scanners. When used with the same object, the measured stiffness values increase in the row: Acuson S2000 → Aixplorer → LOGIQ E9.

Reproducibility of shear wave elastography among operators, machines, and probes in an elasticity phantom

“…Our results support the consensus in the literature that SWE measurements can be considerably different between different machines [ 11 , 13 , 15 , 17 , 19 , 27 , 30 ]. For example, Shin et al [ 19 ] investigated three machines (Aixplorer, ACUSON S3000, and EPIQ 5) and reported inconsistent measurements using curved probes at various depths between 2 cm and 5 cm.…”

“…In terms of measurement bias, our results suggest a significant difference, ranging on average from 16% to 48%, between the measured SWE values and the theoretical values provided by the phantom manufacturer. This finding is consistent across the majority of studies conducted on CIRS phantoms [ 11 , 12 , 14 , 15 , 17 - 21 ]. The only exception was the study of Mulabecirovic et al [ 13 ], who used the 049 model and reported accurate measurements using the GE machine (9L-D probe) and SSI machine (probe 2).…”

“…To date, only one company (Computerized Imaging Reference Systems [CIRS], Norfolk, VA, USA) manufactures quality assurance (QA) elastography phantoms. Their phantoms have been widely investigated, especially models 049 [11][12][13][14][15][16], 049A [17,18], and 039 [19][20][21] for liver fibrosis. However, no studies have investigated the multi-purpose QA phantom (model 040GSE, CIRS), which is equipped with elasticity targets and B-mode imaging test objects [22].…”

Variability, Validity and Operator Reliability of Three Ultrasound Systems for Measuring Tissue Stiffness: A Phantom Study

“…The results may differ if patients move between healthcare institutions employing alternative ultrasound systems; therefore, clinical decision-makers must consider this during clinical practice. Conversion formulae have been suggested to adapt the measurements between ultrasound systems to aid comparability [ 3 ].…”

“…There are several ultrasound systems on the market. Much of the technology and mechanisms behind SWE are patented and, therefore, inaccessible to researchers and clinicians [ 3 ]. However, only a few studies have explored the inter-system accuracy and reliability of different ultrasound systems [ 3 , 6 ].…”