Ch. 8 Transducers Flashcards
During ______ electrical energy from the system is converted into sound.
During transmission electrical energy from the system is converted into sound.
During ______ the reflected sound pulse is converted into electricity.
During reception the reflected sound pulse is converted into electricity.
The __________________________ effect describes the property of certain materials to create a voltage when they are mechanically deformed or when pressure is applied to them.
The Piezoelectric Effect describes the property of certain materials to create a voltage when they are mechanically deformed or when pressure is applied to them.
PZT in ultrasound transducer is also known as the ________________, _______________________, or ___________________.
PZT in ultrasound transducer is also known as the ceramic, active element, or crystal
The ______________ is the cylindrical tube, constructed of metal or plastic, that protects the internal components of the transducer from damage.
The case is the cylindrical tube, constructed of metal or plastic, that protects the internal components of the transducer from damage.
The ________________________ is a thin metallic barrier lining the inside of the case. This helps prevent electrical noise from contaminating the clinically important electrical signals used to create diagnostic images.
The electrical shield is a thin metallic barrier lining the inside of the case. This helps prevent electrically noise from contaminating the clinically important electrical signals used to create diagnostic images.
The ___________________________ is a thin barrier of cork or rubber that isolated or “uncouples” the internal components of the transducer from the case. Also, prevents vibrations in the case from inducing an electrical voltage in the PZT of the transducer.
The acoustic insulator is a thin barrier of cork or rubber that isolated or “uncouples” the internal components of the transducer from the case. Also, prevents vibrations in the case from inducing an electrical voltage in the PZT of the transducer.
The ______________ or _____________________ is the piezoelectric crystal itself. The characteristics of the sound beam emitted by the transducer are related to the deminsions of the active element.
The PZT or active crystal is the piezoelectric crystal itself. The characteristics of the sound beam emitted by the transducer are related to the deminsions of the active element.
The ______________ provides an electrical connection between the PZT and the ultrasound system.
The wire provides an electrical connection between the PZT and the ultrasound system.
The __________________________ is positioned in front of the PZT at the face of the transducer. The matching layer:
- increasing the efficiency of sound energy transfer between the active element and the body
- protects the active element
The Matching Layer is positioned in front of the PZT at the face of the transducer. The matching layer:
- increasing the efficiency of sound energy transfer between the active element and the body
- protects the active element
The ______________________________ is bonded to the back of the active element, it reduces the “ringing” of the PZT.
The Backing Material is bonded to the back of the active element, it reduces the “ringing” of the PZT (enhancing axial resolution)
Gel, Matching Layer, Skin, and PZT… list in discreasing order of impedance:
- PZT
- matching layer
- gel
- skin
The thickness of the _________________________ is ________________________ of the wavelength of sound in the matching layer
The thickness of the matching layer is one-quarter of the wavelength of sound in the matching layer.
The thickness of the _________________________ is __________________________ of the wavelength of sound in the active element
The thickness of the active element is one-half of the wavelength of sound in the active element
What are the three consequences of using backing material?
- decreased sensitivity
- wide bandwidth
- low quality factor
_______________________________ means that during reception, transducers with damping material are less able to convert low-level sound reflections into meaningful electrical signals
Decreased Sensitivity means that during reception, transducers with damping material are less able to convert low-level sound reflections into meaningful electrical signals
________________________ is the range of frequencies in the pulse. It is the difference between the highest and lowest frequencies.
Bandwidth is the range of frequencies in the pulse. It is the difference between highest and lowest frequencies.
_____________________________ is a unitless number that is inversely related to bandwidth.
Quality Factor is a unitless number that is inversely related to bandwidth
Quality Factor formula:
QF = main frequency/bandwidth
A shorter, dampened pulse has a _______ Q-factor.
lower
A longer, undampened pulse has a ___________ Q-factor.
higher
The temperature at which the PZT is polarized is called the ___________________________________ or ___________________________________
The temperature at which the PZT is polarized is called the Curie temperature or Curie Point
_____________________________ is the destruction of all microorganisms by exposure to extreme heat, chemical agents, or radiation.
Sterilization is the destruction of all microorganisms by exposure to extreme heat, chemical agents, or radiation
_____________________________ is the application of a chemical agent to reduce or eliminate infectious organisms on an object.
Disinfection is the application of a chemical agent to reduce or eliminate infectious organisms on an object
Pulse length is [directly or inversely] related to pulse duration.
directly
Q-factor is [directly or inversely] related to bandwidth
inversely
Pulse Duration is [directly or inversely] related to bandwidth
inversely
The sensitivity of transducers that create short duration pulses is likely to be [greater than, less than, or equal to] that of transducers that create long pulses
less than
With continuous wave electrical frequency =
Acoustic frequency
with a pulsed wave transducer, two characteristics of the active element combine to determine the frequency of sound:
- speed of sound in the PZT
- thickness of the PZT
Average speed of sound in most PZT material ranges from 4 to 6 mm/us(about 4 times greater than the speed of sound in soft tissue)
Thickness of PZT crystals in diagnostic imaging transducers range from 0.2 to 1mm
High Frequency Pulsed Wave Imaging Transducers have _________________________ PZT crystals, and PZT with _____________________ speeds.
High Frequency Pulsed Wave Imaging Transducers have thinner PZT crystals, and PZT with higher speeds
Low Frequency Pulsed Wave Imaging Transducers have ____________________ PZT crystals, and PZT with __________________ speeds
Low Frequency Pulsed Wave Imaging Transducers have thicker PZT crystals, and PZT with lower speeds
frequency of pulsed wave imaging transducers equation:
frequency(MHz)= sound’s speed in PZT(mm/us) / 2 x thickness(mm)
