Preclinical evaluation of acoustic radiation force impulse measurements in regions of heterogeneous elasticity.
OBJECTIVE
The purpose of this study was to compare the reliability of ultrasound-based shear wave elastography in regions of homogeneous versus heterogeneous elasticity by using two different probes.


METHODS
Using acoustic radiation force impulse (ARFI) elastography, we measured the shear wave velocity (SWV) in different lesions of an elastography phantom with the convex 4C1 probe and the linear 9L4 probe. The region of interest (ROI) was positioned in such a way that it was partly filled by one of the lesions (0%, 25%, 50%, 75%, and 100%) and partly by the background of the phantom (100%, 75%, 50%, 25%, and 0%, respectively).


RESULTS
The success rate was 98.5%. The measured value and the reference value of SWV correlated significantly (r=0.89, P<0.001). Further, a comparison of the two probes revealed that there was no statistical difference in either the mean or the variance values. However, the deviation of SWV from the reference was higher in the case of the 9L4 probe than in the case of the 4C1 probe, both overall and in measurements in which the ROI contained structures of different elasticity (P=0.021 and P=0.002). Taking into account all data, for both probes, we found that there was a greater spread and deviation of the SWV from the reference value when the ROI was positioned in structures having different elastic properties (standard deviation, 0.02±0.01 m/sec vs. 0.04±0.04 m/sec; P=0.010; deviation from the reference value, 0.21±0.12 m/sec vs. 0.38±0.27 m/sec; P=0.050).


CONCLUSIONS
Quantitative ARFI elastography was achievable in structures of different elasticity; however, the validity and the reliability of the SWV measurements decreased in comparison to those of the measurements performed in structures of homogeneous elasticity. Therefore, a convex probe is preferred for examining heterogeneous structures.
Nephrology Department, Klinikum Rechts der Isar of the Technical University of Munich, Munich, Germany.
Katharina
0000-0003-3555-8330
K
Hollerieth
Meso International GmbH, Berlin, Germany.
Bernhard
B
Gaßmann
Institute for Medical Biometry, Epidemiology and Medical Informatics, Saarland University, Campus Homburg (Saar), Homburg, Germany.
Stefan
S
Wagenpfeil
Nephrology Department, Klinikum Rechts der Isar of the Technical University of Munich, Munich, Germany.
Philipp
P
Moog
Nephrology Department, Klinikum Rechts der Isar of the Technical University of Munich, Munich, Germany.
Minh-Truc
MT
Vo-Cong
Nephrology Department, Klinikum Rechts der Isar of the Technical University of Munich, Munich, Germany.
Uwe
U
Heemann
Nephrology Department, Klinikum Rechts der Isar of the Technical University of Munich, Munich, Germany.
Konrad Friedrich
KF
Stock
Elasticity imaging techniques; Heterogeneity; Phantoms, imaging; Transducers; Ultrasonography