Evaluation of Very-High-Frequency Ultrasound Imaging Characteristics of Dermatofibroma.

Background: Dermatofibroma (DF) is one of the common dermatosis, which is so challenging to diagnose that its misdiagnostic incidence is quite high. The very-high-frequency (VHF) ultrasound is particularly relevant to the diagnosis of . Herein, we analyze the sonographic features and application value of VHF ultrasound in the diagnosis of .

Waveguide invariant focusing for broadband beamforming in an oceanic waveguide.

The performance of broadband sonar array processing can degrade significantly in shallow-water environments when interference becomes angularly spread due to multipath propagation. Particularly for towed line arrays near endfire, elevation angle spreading of multipath interference often results in masking of weaker sources of interest. While adaptive beamforming in a series of narrow frequency bands can suppress coherent multipath interference, this approach requires long observation times to estimate the required narrowband covariance matrices.