Optimization of the excitation beam sequences in Harmonic Motion Imaging for clinical breast tumor characterization

Previous studies from our group have investigated the effects of AM frequencies on the image qualities in Harmonic Motion Imaging (HMI). Higher AM frequencies have been shown to be beneficial in delineating and contrasting stiffer and smaller inclusions. In this paper, adaptive AM frequency selection was studied with the aim to produce consistent inclusion stiffness measurements for inclusions with the same mechanical properties of different dimensions. In addition, simultaneous electronic beam steering of both the FUS excitation and focused imaging for speckle tracking were successfully demonstrated in both experimental phantoms and in vivo clinical patient scans. 200-Hz AM was shown to produce consistent displacement ratio (DR) measurements for inclusions of diameters greater than 6 mm with the same mechanical properties. A higher AM frequency, 400 Hz, was otherwise needed to produce a similar DR measure as larger inclusions with the same Young's modulus did. Using adaptive AM frequency (200 or 400 Hz) selection based on the B-mode images, a linear fit with R ² = 0.8770 was established between the inverse DR and modulus ratio of inclusion to background regardless of the inclusion size.