Detection of electrical conductivity interfaces with ultrasonically-induced Lorentz force
Résumé
An ultrasonically-induced Lorentz force scanner is set up to attempt detecting adipose tissues in biological samples by scanning their electrical conductivity gradients. A preliminary experiment wass conducted where a 500 kHz transducer generated an ultrasound wave with a peak pressure of 1 MPa. The medium, a fat-layered rib, was placed at the focus, 18 to 24 cm away from the transducer, and inside a 300 mT magnetic field created by a permanent magnet. Two electrodes acquired the current induced by Lorentz force, which is averaged 1000 times. Spatial sampling is performed by moving the transducer perpendicularly to the ultrasound axis with steps of 1 cm. The different measured signals allow visualizing the fat layers of the sample, thanks to the high difference of electrical conductivity between the fat and the muscle. The lateral image-resolution is about 5 mm. It is compared with a picture of the sample. This method combines the strength of ultrasound imaging with the capacity to have a different way to characterize the properties of the imaged tissues. However it still suffers from the weakness of the signals to be measured.
Domaines
Acoustique [physics.class-ph]
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