Purpose:Acceptance testing of shear wave elastography on ten ultrasound systems is reported. Furthermore, variations in testing procedures related to coupling medium, number of operators, and phantom homogeneity were investigated.Methods:Shear wave speed measurements were made on ten systems (GE LOGIQ E9 XDclear 2.0 ultrasound scanner with C1‐6 and 9L transducers). Measurements were acquired using the CIRS Model 039 shear wave liver fibrosis phantoms (“soft” and “hard” phantoms, with stiffness of ∼3.5 and 45 kPa, respectively) at two depths (3 and 7 cm for C1‐6; 1 and 4 cm for 9L), by two operators. Each measurement was repeated for five times without specifying the transducer location on the phantom. 45 ppm salt water (as recommended by QIBA) was used for coupling. Furthermore, phantom homogeneity was investigated by comparing C1‐6 measurements made at five positions marked on each phantom. Three operators acquired C1‐6 measurements on one scanner, and one repeated the measurements after a week. US gel was compared with salt water as a coupling medium.Results:Averaged shear wave speed using the ten C1‐6 and 9L transducers are summarized in Table 1. The greatest maximum deviation of an individual measurement from the group mean (Table 2) was 5.4% of the mean and 2.3 times the standard deviation among all groups. Salt water and US coupling gel showed no significant difference. Velocities from the five measurement locations had a maximum deviation of 5.9% or less. The maximum inhomogeneity averaged over the two phantoms and all measurement locations was 2.6%. Inter‐ and intra‐operator coefficients of variation were all ≤ 2.2%.Conclusion:The measurement variations were considered to be reasonable, and all equipment was accepted. The use of salt water versus gel for acoustic coupling, single versus multiple phantom measurement locations, or single versus multiple operators would not cause significant differences in acceptance test results.Pengfei Song and Shigao Chen receive royalties from GE Medical Systems for the shear wave elastography technology.

Purpose:Doppler ultrasound (US) peak velocity (Vmax) measurements show considerable variations due to intrinsic spectral broadening with different scanning techniques, machines and manufacturers. We developed a semi‐automated Vmax estimation method and used this method to investigate the performance of a US system for clinical Doppler Vmax measurement.Methods:Semi‐automated Vmax is defined as the velocity at which the computed mean spectral profile falls to within 1 background standard deviation of the background mean. GE LOGIQ E9 system with 9L and ML6‐15 probes were studied with steady flow (5.3 – 12.5 ml/s) in a Gammex OPTIMIZER 1425A phantom. All Doppler spectra were acquired by 1 operator at the distal end of 5 mm angular tube using a modified clinical carotid artery protocol. Repeatability and variation of Vmax to scanning parameters and probes were analyzed and reported as percentage, i.e. (max‐min)/mean.Results:Vmax estimation had good repeatability (3.1% over 6 days for 9L, and 3.6% for ML6‐15). For 9L probe, varying gain, compression, scale, SV depth and length, and frequency had minimal impact on Vmax (all variations less than 4.0%). Beam steering had slightly higher influence (largest variations across flow rates were 4.9% for 9L and 6.9% for ML6‐15). For both probes, Doppler angle had the greatest effect on Vmax. Percentage increase of Vmax was largely independent of actual flow rates. For Doppler angle varied from 30 to 60°, Vmax increased 24% for 9L, and 20% for ML6‐15. Vmax measured by ML6‐15 were lower than that by 9L at each Doppler angle with differences less than 5%.Conclusion:The proposed Vmax estimation method is shown to be a useful tool to evaluate clinical Doppler US system performance. For the tested system and probes, Doppler angle had largest impact in measured Vmax.

Purpose: The detection of ultrasound artifacts due to transducer failure is important for maintaining image quality. The aim of this study is to evaluate 3 methods for detecting ultrasound artifacts, involving direct evaluation of dynamic B‐mode clips and 2 types of single frame statistical images. Methods: A range of artifacts of varying severity were artificially created for 28 transducers of varying models. The appearance of these artifacts was substantially similar to actual artifacts detected during ultrasound scanner acceptance testing and routine quality assurance. A second set of 28 matching transducers contained no artifacts. A 10 second clip was recorded of a dynamic speckle pattern from a custom liquid phantom (“dynamic clip”). A single‐frame image was obtained by computing the median values at each pixel location over all frames of the clip (“median image”). This single frame median image was then subtracted from a baseline median image previously obtained with no induced artifact (“subtracted median”). All images were evaluated by 6 observers and the mean sensitivity and specificity for the three artifact detection methods estimated. Results: In all cases the dynamic clip had the lowest sensitivity (61%) of the three detection methods. The subtracted median images had the highest sensitivity of 97% and while maintaining a high specificity of 92%. Conclusions: For routine quality control, the use of subtracted median images allows detection of artifacts with very good sensitivity and specificity. For acceptance testing, where there are no previous baseline images available for subtraction, the use of median images is useful, although comparison with median images from different transducers of the same model and/or multiple observers should be made to decrease the incidence of false‐positive findings. If statistical images are not available, direct inspection of the dynamic B‐mode clips is useful for acceptance testing and quality control, but with lower sensitivity.

Purpose: Ultrasound artifacts are often identified by scanning a uniform region of a rigid tissue‐mimicking phantom while moving the transducer across the scan surface, and identifying any deviations from the expected smooth echotexture. Due to the rigid nature of commercial phantoms it is difficult to simultaneously couple the entire face of curved array transducers. We have proposed a novel low cost liquid phantom with a flexible scan surface. The purpose of this work is to demonstrate the proof of concept of this unique phantom. Method and Materials: The phantom consisted of a water/cornstarch solution enclosed in a thin latex balloon (thickness 0.24 mm). When shaken, the cornstarch provides a dynamic speckle pattern. Initial experiments were conducted to establish the basic effectiveness of this innovative phantom to demonstrate artifacts, to assess reproducibility of image acquisition, and inter‐operator variability. The phantom was imaged using an Acuson Sequoia US scanner and 4 transducer models (9L4, 6C2, 4V1 and EC‐10C5), and dynamic clips of the changing speckle field were recorded. Two transducers with independently‐confirmed artifacts were also tested. Results: The flexible scanning surface allowed excellent acoustic coupling of the entire face of all transducer models with the phantom, including tightly curved arrays. Little manual transducer motion was required with the liquid phantom as a result of the dynamic speckle field. Artifacts due to inactive elements were detected, including a single crystal dropout. Using a defined scan protocol, reproducible clips exhibiting low inter‐ and intra‐ operator dependency were obtained by 5 operators with minimal training, for transducers with and without artifacts. Conclusion: Due to its ease of operation, low cost, and sensitivity, this phantom may be superior to current methods of detecting ultrasound artifacts, and has the potential to promote better acceptance and compliance of ultrasound quality control.

Objective: We report an unusual artifact observed recently in clinical ultrasound (US) images obtained during a biopsy. We do not believe that this artifact has been previously described in the literature. The artifact appeared as a comet-like pattern of echogenic signal, which originated at the tip of the biopsy needle and emanated downward, simulating a rough mirror image of the needle. Experiments in test objects as well as numerical calculations were performed to explain the artifact appearance and establish the origin.Methods: A general explanation of the artifact is that it is due to a vibrational wave produced by initial incidence of the US pulse with the needle. This wave travels down the length of the needle, reflects off the needle tip, and travels back the length of the needle, ultimately producing a signal detected by the transducer and mapped into the US image. Experiments were performed to determine whether the wave traveling along the needle was shear or longitudinal in nature. The artifact was replicated in test objects consisting of strips of various metals including aluminum and copper, immersed in a water bath. Measurements of the incident angles, which produced the artifact, as well as the angle between the metal object and the artifact were made, and were compared with theoretical predictions.Results: We found that copper strips produced artifacts for incident angles between 14 and 62 degrees, and the artifact angles varied from 29 degrees and 35 degrees as a function of incident angle. Similarly, for aluminum strips, artifacts were observed for incident angles between 13 and 42 degrees, while the artifact angles varied between 20 degrees and 30 degrees. These results are reasonably consistent with a shear wave explanation. More definitive experiments are in progress.Conclusions: We describe a new artifact observed both clinically and in test objects that results from US waves traveling along the length of a needle or similar metal object. Although our quantitative measurements are not conclusive, it appears most likely that this artifact results from shear, rather than longitudinal waves. Objective: We report an unusual artifact observed recently in clinical ultrasound (US) images obtained during a biopsy. We do not believe that this artifact has been previously described in the literature. The artifact appeared as a comet-like pattern of echogenic signal, which originated at the tip of the biopsy needle and emanated downward, simulating a rough mirror image of the needle. Experiments in test objects as well as numerical calculations were performed to explain the artifact appearance and establish the origin. Methods: A general explanation of the artifact is that it is due to a vibrational wave produced by initial incidence of the US pulse with the needle. This wave travels down the length of the needle, reflects off the needle tip, and travels back the length of the needle, ultimately producing a signal detected by the transducer and mapped into the US image. Experiments were performed to determine whether the wave traveling along the needle was shear or longitudinal in nature. The artifact was replicated in test objects consisting of strips of various metals including aluminum and copper, immersed in a water bath. Measurements of the incident angles, which produced the artifact, as well as the angle between the metal object and the artifact were made, and were compared with theoretical predictions. Results: We found that copper strips produced artifacts for incident angles between 14 and 62 degrees, and the artifact angles varied from 29 degrees and 35 degrees as a function of incident angle. Similarly, for aluminum strips, artifacts were observed for incident angles between 13 and 42 degrees, while the artifact angles varied between 20 degrees and 30 degrees. These results are reasonably consistent with a shear wave explanation. More definitive experiments are in progress. Conclusions: We describe a new artifact observed both clinically and in test objects that results from US waves traveling along the length of a needle or similar metal object. Although our quantitative measurements are not conclusive, it appears most likely that this artifact results from shear, rather than longitudinal waves.