Research On Experimental Of Magneto Acoustic Electric Tomography Based On Laser Induced Ultrasonic

Magneto Acoustic Electric Tomography(MAET)is a new functional imaging technology which combines high contrast of electrical impedance imaging and high resolution of acoustic imaging.At present,traditional MAET uses piezoelectric ultrasonic transducer as the ultrasonic excitation source.In order to avoid the strong electromagnetic interference of the ultrasonic transducer in the strong magnetic field,the piezoelectric ultrasonic transducer must be located outside the magnetic field,so it has to keep a distance of 3cm-5cm.This distance not only causes the loss of ultrasound in the transmission process,but also is not conducive to the further clinical application.In this thesis,a laser induced ultrasonic transducer(LIUT)based on photoacoustic effect is designed,the ultrasonic performance test of the new LIUT,the built of a magneto-acoustic-electric imaging experimental platform and the feasibility test are studied.First,this thesis has designed and produced LIUT based on carbon nanotubes(CNT)-Polydimethylsiloxane(PDMS),its ultrasonic performance was tested experimentally.The laser irradiated LIUT directly after beam expansion collimation,the sound field generated by laser irradiated LIUT was tested with a needle hydrophone.The test results showed that the sound pressure at the position of 2.7cm from the LIUT center could reach 3.9MPa,the ultrasonic frequency range was 2.5MHz-7.9MHz.Secondly,the MAET experimental platform was built based on LIUT made of CNT-PDMS composite film.The ultrasonic was generated by 532 nm pulsed laser excitation of LIUT.The generated ultrasonic and static magnetic field acted on the conductive target.Due to lorentz force effect,an equivalent electric field source is generated in the target body,the electrical signal received by the electrode attached to the conductive target body can reflect the electrical information of the target imaging body.In the experiment,the hydrogel was used as the conductive target.Ccopper foil of 0.1mm thick was placed in the vertical sound field of the hydrogel as the abnormal conductive body.The experimental results showed that when the distance between LIUT and the abnormal conductive body was 2.8cm,the magneto-acoustic-electrical signal could be observed through the oscilloscope.At 18.5?s,the magneto-acoustic-electrical pulse signal generated by theabnormal conductive body.Furthermore,the anomalous body was placed at a distance of1.6cm from the LIUT,magneto-acoustic-electrical pulse signal generated by the anomalous body and could be clearly observed at the position of 11.2?s.Combined with the ultrasonic transmission characteristics,the feasibility of the MAET based on LIUT experiment was verified.Finally,make use of stepper motor step scan conductive abnormal body.At the same time,the LIUT at a distance of 2.8 cm from conductive abnormal body in static magnetic field.Scan step is 5 mm,and scan length is 5.5 cm.B scan images can present the boundary information of conductive abnormal body in hydrogel clearly.Furthermore,proving the MAET experiment based on LIUT method is feasible,also shows that the technology application prospect in the field of nondestructive testing and biological imaging is wide.