Advances in ultrasound elasticity imaging

The most troublesome of ultrasonic B-mode imaging is the difficulty of accurately diagnosing cancers, benign tumors, and cysts because they appear similar to each other in B-mode images. The human soft tissue has different physical characteristics of ultrasound depending on whether it is normal or not. In particular, cancers in soft tissue tend to be harder than the surrounding tissue. Thus, ultrasound elasticity imaging can be advantageously used to detect cancers. To measure elasticity, a mechanical force is applied to a region of interest, and the degree of deformation measured is rendered as an image. Depending on the method of applying stress and measuring strain, different elasticity imaging modalities have been reported, including strain imaging, sonoelastography, vibro-acoustography, transient elastography, acoustic radiation force impulse imaging, supersonic imaging, and strain-rate imaging. In this paper, we introduce various elasticity imaging methods and explore their technical principles and characteristics.

Vibroacoustography for the assessment of total hip arthroplasty

OBJECTIVES: This paper proposes imaging with 3-dimensional vibroacoustography for postoperatively assessing the uncovered cup area after total hip arthroplasty as a quantitative criterion to evaluate implant fixation. METHODS: A phantom with a bone-like structure covered by a tissue-mimicking material was used to simulate a total hip arthroplasty case. Vibroacoustography images of the uncovered cup region were generated using a two-element confocal ultrasound transducer and a hydrophone inside a water tank. Topological correction based on the geometry of the implant was performed to generate a 3-dimensional representation of the vibroacoustography image and to accurately evaluate the surface. The 3-dimensional area obtained by the vibroacoustography approach was compared to the area evaluated by a 3-dimensional motion capture system. RESULTS: The vibroacoustography technique provided high-resolution, high-contrast, and speckle-free images with less sensitivity to the beam incidence. Using a 3-dimensional-topology correction of the image, we accurately estimated the uncovered area of the implant with a relative error of 8.1% in comparison with the motion capture system measurements. CONCLUSION: Measurement of the cup coverage after total hip arthroplasty has not been well established; however, the covered surface area of the acetabular component is one of the most important prognostic factors. The preliminary results of this study show that vibroacoustography is a 3-dimensional approach that can be used to postoperatively evaluate total hip arthroplasty. The favorable results also provide an impetus for exploring vibroacoustography in other bone or implant surface imaging applications. .