Distinguishing fluid and solid breast masses with fundamental and harmonic amplitude- and coherence-based ultrasound beamforming

Harmonic imaging has demonstrated potential to improve B-mode and short-lag spatial coherence (SLSC) image quality by reducing acoustic clutter. In addition, our group previously demonstrated that robust SLSC (R-SLSC) distinguishes solid from fluid masses in breast ultrasound. However, a combined harmonic R-SLSC imaging approach has not been previously explored. This work is the first to investigate the ability of both harmonic B-mode and harmonic R-SLSC images to distinguish solid from fluid-filled breast masses in comparison to their fundamental imaging counterparts. Raw ultrasound data from 18 breast masses were acquired and beamformed to obtain matched fundamental and harmonic B-mode and R-SLSC images. Clutter reduction with harmonic imaging resulted in up to 4.2 dB contrast improvement in harmonic B-mode images compared to fundamental B-mode images, yet led to increased spatial coherence within the hypoechoic masses. Therefore, the contrast of fluid masses in harmonic R-SLSC images was 7.02-12.5 dB worse than that of fundamental R-SLSC images. The generalized contrast-to-noise ratio was implemented as an objective discriminator of fluid and solid masses with 100% and 94% accuracy achieved with fundamental and harmonic R-SLSC imaging, respectively. These results suggest that although harmonic imaging reduces clutter, fundamental R-SLSC is better suited to distinguish solid from fluid breast mass contents.