R Mohammadi - Biomedical Engineering Department, Tarbiat Modares University
A Mahloojifar - Biomedical Engineering Department, Tarbiat Modares University
H Zayyani

ultrasonic microscope or Scanning Acoustic Microscope (SAM) is a powerful tool for biological tissue characterization. Characterization of thin sliced tissue is difficult, as the reflected signals from tissue top and bottom are superimposed. To determine thin tissues having micrometer thicknesses, high acoustic frequencies are required for conventional SAM systems. The acoustic frequency used in practice is limited by its penetration depth through the tissue. In this paper, in order to improve the axial resolution of conventional scanning acoustic microscopy, a new SAM technique based on sparse signal representation in overcomplete time-frequency dictionaries is investigated and among great number of algorithms for finding sparse representation of signal, we apply MP and OMP algorithms. Different criteria are used for measuring this technique performance for various SAM applications, such as waveform estimation, echo detection and C-scan imaging. Simulation results show that this method has higher resolution comparing with conventional SAM methods.