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Beyond the distance they usually show towards politics — a condition of legitimacy in carol hipps perte de poids securitarian system introduced in Science. The new technique, henceforth referred to as "Acousto-Electric Conductivity Modulation" AECM imaging, is based on the interaction of a sound wave with an electrical field.
In its simplest form, four electrodes located near the region to be imaged apply a low-amplitude electrical current and measure the potential difference arising from current flow in the tissues. A focused ultrasound transducer directs a pressure wave to a voxel of the region of interest, modifying its conductivity distribution and, as a result, the amplitude of the potential measured by the electrodes. An image of the conductivity distribution can thus be constructed point-by-point by moving the electrodes and transducer to scan the object.
In this context, the acoustic wave acts as the localization agent while the electrical potential provides a measure of the local conductivity change that occurs in the voxel.
The first model presented in the thesis is based on the use of bipolar acoustic waves for excitation. This waveform is generally used with narrow band transducers.
Acoustic waves generated by an ultrasound transducer driven with a burst of sine waves consists of alternating compression and rarefaction phases which tend to cancel each other in terms of the conductivity changes they produce. However when the thickness of the target object is small compared to the wavelength of the acoustic wave, this cancelling effect will not occur and the AECM signals will have sufficiently high amplitude to achieve image reconstruction using successive transducer positions to scan the region of interest.
By extracting from the spectra of the AECM signals the amplitude of the peak at the excitation frequency, a map of the acousto-electric sensitivity of the system can be obtained. This map is then.