Tissue Characterization Of HIFU Thermal Ablation Based On Ultrasound Pulse-echo RF Signals

OBJECTIVE: This study is research on the tissue characterization ofHIFU thermal ablation based on the B ultrasonic pulse-echo RF signal, usetissue characterization methods to monitor the coagulation tissue afterHIFU treatment, and to explore the feasibility of monitor the coagulationtissue without strong echoes through tissue characterization methods.METHODS: Control HIFU focus on the bovine liver and make itproduce coagulation necrosis, and collect the original RF signals before andafter HIFU treatment, compare and analyze these RF signals, extract theIBS, FD and Rényi entropy of RF signals, and scan convert to sectorultrasonic tissue characterization image, then compare and analyze thetissue characterization image with the B-mode ultrasonic image andanatomical image, to explore the feasibility and accuracy of tissuecharacterization method. RESULT: The collected experimental data are generally divided intotwo types: one kind is the tissue exist HIFU lesion and B-mode ultrasoundimage appears strong echoes; another is the tissue exist HIFU lesion butultrasound image without strong echoes. To process these two types datause tissue characterization methods mention in the chapter two of this paperand found that:.1. When the tissue exist HIFU lesion and B-mode ultrasound imageappears strong echoes, all of these three types of tissuecharacterization image can reflect the tissue texture information,and the AD, SAD, SSD differential subtraction images show thesize and position of the coagulation necrosis area obviously,consistent with the anatomical image basically;2. When the tissue exist HIFU lesion but B-mode ultrasound imagewithout strong echoes, all of these three types of tissuecharacterization image can’t show the position and size ofcoagulation necrosis area obviously, however the AD, SAD, SSDdifferential subtraction images can show the coagulation necrosisarea faintly, but the position and size exist some deviation,temporarily can’t applied in the clinical.CONCLUSION: When the tissue exist HIFU lesion but B-modeultrasound image without strong echoes, the changes of RF signals amplitude and frequency caused by the coagulation necrosis of tissue isvery weak relative to other signals, which is affect with tissue throughmultiple reflection and scattering, it has been a mixture of a variety of othertissue characteristics when received by probe, tissue characterizationparameters extracted on this basis must be biased. While when the tissueexist HIFU lesion and B-mode ultrasound image appears strong echoes,there are a large number of bubbles and bubble nuclei in the coagulationnecrosis area, caused some strong reflection signal and scattering signal on,which represents the tissue characteristics of coagulation necrosis, andbecause of these signals are strong, less susceptible to interference, so canextract the tissue characteristics accurately under this situation.