Imaging techniques in radiology 1
Lecture 1 8 feb 2022
System diagram
System diagram
Piezoelectric elements
,Different acquisition modes
A-Mode and B mode (amplitude and brightness mode)
A-Mode, or Amplitude Modulation, is the display of amplitude
spikes as a function of depth. (single line)
B-Mode, or Brightness Mode, is the 2D display of gray scale values
as a function of depth.
M-mode
M-Mode, or Motion Mode, is the display of a one-dimensional image that is used for
analyzing moving body parts commonly in cardiac and fetal cardiac imaging.
,Interaction types
Reflection
Reflection in ultrasound refers to the return of the sound wave energy back to the
transducer and contributes to the image formation.
Specular reflection
Angle of incidence = angle of reflection
Acoustic shadowing (artefact)
Marked reduction in the intensity of ultrasound deep to a strong reflector or attenuator
, Mirror artefact
Reverberation artefact
When the ultrasound signal reflects repeatedly between highly reflective interfaces that are
usually near the transducer. Reduced by changing the scan angle and placement of the
transducer.
Diffuse reflection (scattering)
Rough surfaces or materials with particle dimensions with size ≤ wave length
Refraction
Change of transmitted ultrasound beam at a tissue boundary between two media in which
ultrasound travels at different velocities (Snell’s law)
Unlike reflection, refraction does not contribute usefully to the image formation. The
reflected sound beam travels away from the transducer resulting in loss of the propagated
signal.
Lecture 1 8 feb 2022
System diagram
System diagram
Piezoelectric elements
,Different acquisition modes
A-Mode and B mode (amplitude and brightness mode)
A-Mode, or Amplitude Modulation, is the display of amplitude
spikes as a function of depth. (single line)
B-Mode, or Brightness Mode, is the 2D display of gray scale values
as a function of depth.
M-mode
M-Mode, or Motion Mode, is the display of a one-dimensional image that is used for
analyzing moving body parts commonly in cardiac and fetal cardiac imaging.
,Interaction types
Reflection
Reflection in ultrasound refers to the return of the sound wave energy back to the
transducer and contributes to the image formation.
Specular reflection
Angle of incidence = angle of reflection
Acoustic shadowing (artefact)
Marked reduction in the intensity of ultrasound deep to a strong reflector or attenuator
, Mirror artefact
Reverberation artefact
When the ultrasound signal reflects repeatedly between highly reflective interfaces that are
usually near the transducer. Reduced by changing the scan angle and placement of the
transducer.
Diffuse reflection (scattering)
Rough surfaces or materials with particle dimensions with size ≤ wave length
Refraction
Change of transmitted ultrasound beam at a tissue boundary between two media in which
ultrasound travels at different velocities (Snell’s law)
Unlike reflection, refraction does not contribute usefully to the image formation. The
reflected sound beam travels away from the transducer resulting in loss of the propagated
signal.
