Harmonic Concise Atoms for Mean Scatterer Spacing Estimation in the Normal and Ablated Liver Tissues

In this paper, harmonic concise atoms for the mean scatterer spacing (MSS) estimation was proposed to distinguish the normal and the ablated liver tissues. First, the second harmonic RF echo signals are separated with the Butterworth bandpass filter from the ultrasound RF echo signals, and a series of Gabor atoms are found to represent the local components with the concentrated energy. Then, the concise atoms are selected from the found Gabor atoms to optimal match the coherent components in the harmonic signals. Finally, the locations of the adjacent concise atoms are used to estimate the MSSs. In the microwave ablation experiments, the fundamental and second-harmonic RF echo signals were collected from the regions of interest in the normal untreated porcine tissues and thermally coagulated tissues ablated for 300 s, respectively. The MSSs, as well as the means and standard deviations of the MSSs were calculated from the collected signals for further comparation. The experiment results showed that the harmonic-based MSSs had large difference between the normal and the ablated liver tissues. The decrement in the harmonic-based mean MSS, and standard deviation in the ten tissues were 56.33 %, and 8.33 % greater than the fundamental-based results. It indicated that the harmonic-based MSS results with the concise atoms could improve the MSS estimation accuracy to distinguish the normal and the thermal coagulated liver tissues induced by the microwave ablation.