Magneto-Acoustic-Electrical Tomography (MAET) is a multi-physics coupling imaging technology based on the principle of Hall effect, which can be used to detect the electrical conductivity distribution in tissues. Traditional MAET is considered to occur in soft tissue medium, which is regarded as fluid when calculating. But in fact, there are some solid media in human body that will affect our detection, such as skull. Based on the head, this paper analyzes the influence of solid medium on MAET process. Using finite element software, the influence of skull on sound field and electric field is analyzed firstly, and MAET signal of head considering the skull is obtained. The results preliminarily verify the feasibility of applying MAET to the situation with solid medium.
Polydimethylsiloxane/multi-walled carbon nanotube (PDMS/MWCNT) composite had high photoacoustic transduction efficiency owing to its high light absorption coefficient and low interfacial thermal resistance. The high expansion coefficient and light absorption ability of PDMS/MWCNT nanocomposite films have significant positive effects when it is used as a laser ultrasonic transducer. We introduce an ultrasonic-assisted forced impregnation method for the preparation of PDMS/MWCNT nanocomposite films. PDMS was used as the matrix phase, and MWCNTs were used as the nano-supporting framework. PDMS matrix was introduced into the MWCNT framework by the forced impregnation method. The morphology, thermal, and mechanical properties of the nanocomposite film were analyzed systematically. The photoacoustic conversion efficiency was researched through both experiment and simulation methods. The output sound pressure of our PDMS/MWCNT nanocomposite film reached 7.59 MPa when applied as an ultrasonic transducer under the pulsed laser excitation of 1 mJ / pulse energy. The photoacoustic conversion efficiency of our sample was 9.98 × 10 − 4, three times higher than similar products reported before, which offered the possibility to greatly enhance the photoacoustic signals.
In this paper, a concave carbon-based polymer nanocomposite film was developed for high-amplitude focused ultrasound. The composite films consisting of candle soot nanoparticles (CSNPs) and elastomeric polymers were used as the high-frequency optoacoustic sources. To generated focused ultrasound, these composite films were formed on concave optical lens. A focal waveform with peak to peak pressure of ~45 MPa was achieved at the focal point. The prototyped laser-induced focused ultrasound (LIFU) was applied with noninvasive sonothrombolysis in vitro. For enhanced cavitation effect, we demonstrated a spatio-temporal superposition approach of LIFU treatment in conjunction with low-frequency focused ultrasound from a piezoelectric ultrasound transducer. The in vitro results showed that dualfrequency excitation ultrasound treatment can achieve the sonothrombolysis efficiency of approximately 28% in half of an hour (2 mg/min), suggesting that LIFU generated from composite films may be promising in precision sonothrombolysis.
In this work, a magneto-acousto-electrial tomography (MAET) method based on laser-generated ultrasound excitation was proposed for high-spatial-resolution images of the impedance of conductive media. Optically generated ultrasound is reported with broad bandwidth and insensitive to electromagnetic interference (EMI). Composite films were used as the optoacoustic sources, which composed of candle soot (CS) and elastomeric polymers. To characterize the laser-generated ultrasonic waves, laser Doppler vibrometer was adopted as the detecting device making the system totally optical while maintaining millimeter-level resolution and detective depths of several centimeter. Photoacoustic waves were then introduced to a sample of different conductivity distribution by laser-generated ultrasound transmitter at one point and detected by a pair of electrodes on the surface of the sample. Due to the absence of EMI between acoustic excitation and magnetic field, the combination of non-electronic ultrasound generator and low-cost, non-invasive MAET have shown its great capacity for effective early tumor assessment.
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