چكيده به لاتين
Abstract
The use of ultrasonic energy for the treatment of breast and prostate cancers because of its less-invasive nature made it common and useful. HIFU lesion is a hot and stiff region in a acoustic focal area.Consequently, monitoring the process of ablation and lesion detection is an essential issue.
Ultrasound-based tissue characterization has been an active field of cancer detection in the past decades. The main concept behind various techniques is that the returning ultrasound echoes carry tissue-dependent information that can be used to distinguish tissue types. Recently, a new paradigm for tissue typing has been proposed which uses ultrasound Radio Frequency (RF) echoes, recorded continuously from a fixed location of the tissue, to extract tissue-dependent information. This is hereafter referred to as RF time series.
The main purpose of this study is nonlinear analysis of RF time series echoes in order to quantifying the properties of ablated and normal tissue as a result of HIFU treatment. The six fresh ex vivo porcine muscle tissue samples were exposed to HIFU ablation for different acoustic powers of 10, 30,50,70,90,110 W. In this study, Lyapunove exponent, Higuchi fractal dimension, Shanon entropy, weighted entropy and scaling parameter of nakagami distribution were calculated. The result of entropy in the acoustic power of 110 W, CSR value of 22 times higher than B-mode images were obtained. Morever, best results of depth estimation by using the entropy parameter and scaling parameter in acoustic powers of 70 and 90 W were 2.36% & 3.07% and 18.79% & 19.11% ,respectively.
Keywords : High-intensity focused ultrasound, nonlinear analysis, ultrasound RF time series, Entropy imaging.
