Speed of sound imaging: improved image quality in breast sonography

The purpose of this study was to evaluate blindly breast ultrasound images corrected for the speed of sound in breast tissue compared with conventional images.

In this study, 409 images from 153 patients were obtained on an Antares Ultrasound system. The system was modified to process the radiofrequency data with the standard 1540 m/s as the speed of sound and at a corrected speed of sound for breast tissue. An offline MATLAB-developed program randomized the image pairs, and 3 blinded reviewers who were unaware of the new technique reviewed these. The reviewers were asked to rate the image quality of the pair on a 5-point scale (right++, right+, equal, left+, left++). Comments on differences in the images were also recorded.

Conventional images were graded much better in 0.0% and better in 15.1% +/- 6.2%. Corrected speed of sound images were rated much better in 10.5% +/- 14.3%, better in 48.4% +/- 14.3%, and equal in 25.9% +/- 27.6%. Improvements in image quality with corrected speed of sound images included better margin characterization and improved resolution of calcifications.

Correcting for the speed of sound in breast ultrasound improved the overall image quality in 59% of cases, whereas 26% were of similar quality. Specific improvements noted included better characterization of mass margins, tissue interfaces, and depiction of calcifications.