Transducers Flashcards
What is a transducer?
A device that converts one form of energy into another
What does an ultrasound transducer do?
Transmits and receives ultrasound signals
What is the purpose of the case in an ultrasound transducer?
Protects internal components and insulates the patient from electrical shock
What is the function of the electrical shield in a transducer?
Prevents electrical noise from contaminating important signals
What is the role of the acoustic insulator in a transducer?
Isolates internal components from the case to prevent induced voltage
What is PZT in the context of ultrasound transducers?
Lead zirconate titanate, the piezoelectric crystal used in transducers
What is the purpose of the matching layer in a transducer?
Increases efficiency of sound energy transfer between the active element and the body
What does the backing layer or damping element do?
Reduces ringing and creates short-duration pulses
Define the term ‘transmission’ in ultrasound.
The process of converting electrical energy into sound
What is ‘reception’ in the context of ultrasound?
The process of converting reflected sound pulses back into electrical signals
What is the piezoelectric effect?
The ability of certain materials to generate voltage when mechanically deformed
What are piezoelectric materials?
Materials that convert sound into electricity and vice versa
What is decreased sensitivity in ultrasound transducers?
The reduced ability to convert low-level sound reflections into meaningful signals
Define ‘bandwidth’ in ultrasound.
The range of frequencies in a pulse, calculated as highest frequency - lowest frequency
What is the quality factor in ultrasound?
The main frequency divided by bandwidth, a unitless number
What is Curie Temperature?
The temperature at which PZT is polarized, typically 300 - 400 degrees Celsius
Fill in the blank: The _______ effect refers to piezoelectric materials changing shape when a voltage is applied.
Reverse Piezoelectric
What is the main function of the wire in an ultrasound transducer?
Provides electrical connection between the PZT and the ultrasound system
What is polarization in the context of piezoelectric materials?
The process by which piezoelectric materials are exposed to a strong electrical field while being heated to a substantial temperature (the Curie Temperature)
This process aligns the dipoles in the material, enabling it to generate electrical charge under mechanical stress.
What is depolarization?
The loss of piezoelectric properties due to exposure of temperatures exceeding the Curie point
U/S transducers should only be disinfected with Cidex or other cold germicides to avoid depolarization.
Define sterilization.
The destruction of all microorganisms by exposure to extreme heat, chemical agents, or radiation
What is disinfection?
The application of a chemical agent to reduce or eliminate infectious organisms on an object; attempts to significantly reduce the microbial load
What is the function of a Matching Layer in ultrasound transducers?
Provides acoustic impedance similar to PZT
This helps to improve the efficiency of sound transmission between the transducer and the tissue.
What are the characteristics of a high-frequency PW imaging transducer?
PZT crystals with higher speeds, thickness of ½ wavelength thick
This results in improved axial resolution.
List the consequences of using a high-frequency PW imaging transducer.
- Decreased sensitivity
- Wide bandwidth (broadband)
- Low quality factor (QF)
What are the characteristics of a Continuous Wave Transducer?
- Pulses with long duration and length (continuous wave)
- No backing material
- Increased sensitivity
- Narrow bandwidth
- Higher Q-factor (due to no off-time)
How is the acoustic frequency determined in a Pulsed Wave Transducer?
By two characteristics:
* Speed of sound in the PZT (4–6 mm/us)
* Thickness of the PZT (0.2 - 1 mm)
Fill in the blank: The equation for calculating frequency in MHz for a Pulsed Wave Transducer is f (MHz) = _______.
Sound’s Speed in PZT (mm/us) / (2 x thickness of PZT (mm))
What defines the characteristics of a low-frequency PW imaging transducer?
Thicker PZT crystals and PZT crystals with slower speeds
What is the purpose of damping material in ultrasound transducers?
To limit ringing and improve image quality
Damping material helps to enhance the axial resolution by reducing the duration of the ultrasound pulses.
What are imaging transducers also referred to as?
Pulsed Wave Non-Imaging (PWN) transducers
