Envelope Statistics and Backscattered Power-Spectrum Analysis of Rat Livers with High-Frequency Annular Array

High-frequency ultrasound (HFU, >20 MHz) and quantitative ultrasound (QUS) methods provide a means to understand the relationship between anatomical and acoustical characteristics. However, the depth of field (DOF) of HFU transducers is limited which constrains the range where QUS parameters can be estimated. In this study, we aim to improve the accuracy of HFU QUS based-parameters on the envelope statistics and backscattered power-spectrum analysis by using an annular array that allows for an extended DOF. A 20-MHz annular-array transducer with 5 elements (total aperture: 10 mm, geometric focus: 31 mm) was employed to obtain transmit-to-receive signals from each element pair data were beamformed in post-processing. Low scattering concentration phantoms were scanned with 30-μm step size. For the envelope statistics, we estimated the QUS parameters with a Nakagami distribution. For the backscattered power-spectrum analysis, we estimated the scatterer diameter. The μ and scatterer size were homogeneous values versus depth for the annular-array analysis with beamforming. In the simply summed, non-beamformed case, the μ was larger than the beamforming case near the array.