Module 2: Pulsed Ultrasound and Transducers Flashcards
Describe the Piezoelectric effect
When an electric current is applied to a piezoelectric crystal, it vibrates, these vibrations generate sound waves.
Thus, piezoelectric crystals can convert electric currents into ultrasound waves.
Repetition frequency
Frame rate
The number of ultrasound images displayed in one second.
Expressed in Hertz (Hz).
Spatial pulse length
The length of time that an ultrasound pulse occupies in space.
Pulse duration (PD)
Duration of the transmitted pulse.
The time interval from the beginning of the pulse to the end of the pulse
Measured in units of time (s,sm)
Pulse repetition frequency (PRF)
The number of pulses emitted per second.
Measured in units of frequency (Hz, kHz or MHz).
Be able to calculate max frame rate
Describe the main types of transducers
Linear
High-frequency probe
Wide footprint
Piezoelectric crystal arrangement is linear
Frequency is 2.5Mhz - 12Mhz.
Best probe to view the superficial structures
Breast, thyroid, tendons, and blood vessels
Explain the various layers of a typical ultrasound transducer
Acoustic lens
Acoustic mathcing layer
Piezoeletric element (transducer)
Backing material
Describe the main types of transducers
Phased
Small footprint
High temporal resolution and penetration
Cardiac, transcranial, abdominal, and pediatrics
Describe the main types of transducers
Curved
Wider field of view for larger or deeper structures
Abdomen, obstetrics/gynecology (OB/GYN), urology, and some musculoskeletal (MSK)
Describe the main types of transducers
Matrix
Lateral resolution
Axial resolution
Resolution along the axis of the ultrasound beam.
Contrast resolution
Ability to distinguish between different echo amplitudes/image intensity.
E.g., Differtiate between liver and spleen
Temporal resolution
Time from the beginning of one frame to the next.
Ability to visualize moving objects.
Explain focussing of the beam
Creating a narrow point in the cross-section of the ultrasound beam called the focal point.
It is at the focal point where the lateral resolution of the beam is the greatest.
Before the focal point is the near field or Fresnel zone, where beams converge.
Relationship between pulse repetition frequency and pulse repetition
Explain the origins of sidelobes
Side lobes originate outside of the main ultrasound beam, they appear as specular or diffuse artifactual echoes.
How can sidelobes be reduced or avoided
Explain beamwidth
The width of the beam is inversely related to the frequency.
Higher the frequency narrower is the beam.
Explain slice thickness
Explain the different modes of ultrasound
A-mode
Explain the different modes of ultrasound
B-mode
Explain the different modes of ultrasound
M-mode
Pulse repition period (PRP)
Time from the beginning of one pulse to the beginning of the next pulse.
Measured in units of time (s,ms)
