An improved noise robust localized motion imaging for monitoring HIFU treatment

High intensity focused ultrasound (HIFU) is a minimally invasive treatment modality for cancerous tumors. The monitoring of HIFU treatment is extremely important. Localized motion imaging (LMI) is a HIFU monitoring method basing on Harmonic motion method (HMI). It estimates the coagulation length by detecting the change of tissue stiffness. However, the previous LMI is not robust to noise, thus two techniques are employed to improve its noise robustness in this study. First, dynamic cross correlation window (DCCW) is used to obtain vibration amplitude with noise suppression. Second, vibration-frequency band pass filter (VBPF) is employed to calculate the amount of vibration with expected frequency. The qualitative evaluation indicates that the two techniques are able to suppress the affection of noise on the vibration amplitude and vibration amount, respectively. Furthermore, the quantitative comparison demonstrates that the improved LMI is able to give higher accuracy of coagulation length estimation than the previous LMI, and it reduces the root mean square error (RMSE) from 2.52 to 1.84 mm. In this article, an improved noise robust LMI is proposed for monitoring HIFU treatment.