Concerning the construction of a single ultrasound transducer probe:

1.	Concerning the construction of a single ultrasound transducer probe: a. It contains a piezoelectric crystal usually made of lead zirconate titanate (PZT) b. During the manufacturing process, the crystal is heated above the Curie point and is polarized by an external voltage, which is maintained until the temperature falls below the Curie point c. At the resonant frequency, the transducer produces ultrasound of a wavelength equal to half the thickness of the crystal d. To match the properties of the piezoelectric element and the tissue, a matching layer is applied to the surface of the PZT with the acoustic impedance being a geometric mean of PZT and tissue, and thickness equal to half the wavelength produced at the resonant frequency e. The acoustic impedance of the backing layer used to dampen the transducer needs to be identical to that of the piezoelectric crystal
Answer» a. True. b. True. This orientates the internal dipoles in one direction, giving the crystal its piezoelectric properties. Once the crystal is cooled below the Curie temperature, this orientation is preserved, even in the absence of an external voltage. Heating above the Curie point in the absence of an external voltage would result in destruction of this polarization and elimination of the piezoelectric properties. c. False. The wavelength produced at the resonant frequency is double the crystal thickness. d. False. The thickness of the matching plate equals a quarter of the wavelength. e. False. In this case, all the sound energy would be completely absorbed in the backing layer. Therefore, a backing layer of impedance slightly lower than that of the PZT is used.

Concerning the construction of a single ultrasound transducer probe: a. It contains a piezoelectric crystal usually made of lead zirconate titanate (PZT) b. During the manufacturing process, the crystal is heated above the Curie point and is polarized by an external voltage, which is maintained until the temperature falls below the Curie point c. At the resonant frequency, the transducer produces ultrasound of a wavelength equal to half the thickness of the crystal d. To match the properties of the piezoelectric element and the tissue, a matching layer is applied to the surface of the PZT with the acoustic impedance being a geometric mean of PZT and tissue, and thickness equal to half the wavelength produced at the resonant frequency e. The acoustic impedance of the backing layer used to dampen the transducer needs to be identical to that of the piezoelectric crystal

Answer»

a. True.

b. True. This orientates the internal dipoles in one direction, giving the crystal its piezoelectric properties. Once the crystal is cooled below the Curie temperature, this orientation is preserved, even in the absence of an external voltage. Heating above the Curie point in the absence of an external voltage would result in destruction of this polarization and elimination of the piezoelectric properties.

c. False. The wavelength produced at the resonant frequency is double the crystal thickness.

d. False. The thickness of the matching plate equals a quarter of the wavelength.

e. False. In this case, all the sound energy would be completely absorbed in the backing layer. Therefore, a backing layer of impedance slightly lower than that of the PZT is used.

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