ABSTRACT
Objective To research the influence of the thermoacoustic effect for the frequency of the magnetoacoustic signals in the magnetoacoustic tomography (MAT).Methods Some experiments were designed,and the magnetoacoustic signals and the thermoacoustic signals of several materials with different conductivities were analyzed and compared in the time domain and the frequency domain respectively,of which,copper and graphite were high-conductivity materials,and agar and pork were used as low-conductivity biological or similar tissue.Results The characteristics of the magnetoacoustic signals and the thermoacoustic signals of different materials were acquired.The results illustrated that there was a little drop in frequencies of acoustic signals of the materials with high conductivities while a big drop in frequencies of signals of the tissue-like materials comparing with the stimulant pulse.Furthermore,the main frequencies of acoustic signals were not accordant but much lower than the stimulant ones. Conclusion It is found that the thermoacoustic effect is related to the frequency of the acoustic signals. The drop in the center frequencies of the acoustic signals could be explained by the thermoacoustic effect of materials.The acoustic signals with lower main frequencies have the higher proportion of thermoacoustic signals.The studies could contributing to optimizing MAT method and improving MAT imaging quality.
ABSTRACT
Biological ultrasonic (US),photoacoustic (PA) and magnetoacoustic (MA) imaging techniques had similar imaging principles and complementary characteristics.Combined US,PA or MA imaging can provide joint images of biological tissues which present complementary information for more comprehensive characterization of tissues in contrast to single imaging technique.The pathological tissues could be precisely located and their morphology and composition could be accurately identified.This review presented current progresses in combined PA-US,MA-US and US-PA-MA imaging techniques,espeically endoscopic imaging,focusing on the technical aspects of integration and their applications in biomedicine.