Noise Reduction of Nonlinearity Parameter Estimation by Multiple Median Filtering

The “nonlinearity parameter” is an important parameter for ultrasonics and acoustics. “B/A” is commonly used to represent this parameter. It can be used to quantify the level of nonlinear response of a medium affected by sound wave interactions. The magnitude of the 2nd harmonic generation is proportional to B/A. Previous studies have demonstrated that many pathological tissues have a higher B/A than do healthy tissue. Tissue harmonic imaging ( THI ) exploits this difference, allowing lesions to be presented on ultrasound B-mode images. Although this technique has been commercially used for a long time, some studies have considered it to be no help in diagnosis because of its poor lesion visibility. As mentioned above, B/A can directly reflect the healthy or pathological states of tissues. For this reason, increasingly many studies have attempted to use the nonlinearity parameter as a new imaging signal for medical ultrasound imaging. A new technique with lesion visibility better than that of THI is needed, so the technique in question presents our field a rare opportunity to replace traditional ultrasonic technology. The newest proposed estimation method, “Extended Comparative Method” ( ECM ), has been proposed to estimate B/A correctly in the ultrasound field. ECM can also be applied to B-mode image signals only if speckle noise is suppressed. To address this issue, we propose multiple median filtering as a solution. This filtering method is highly effective when the input signal-to-noise ratio ( SNR ) is sufficiently low, but the performance of this method happens to be restricted by low input SNR.