Cpt 10 Notes Flashcards
Describes the detail that is displayed an determines the image accuracy
Resolution
More/better/higher resolution means a _________ picture.
More accurate
Types of resolution:
Axial
Lateral
Temporal
Elevational
The ability of the system to display 2 structures parallel to the sound beam’s axis is ______
Axial resolution
Shorter pulses= _______ image quality
better
Axial resolution units:
mm (any distance)
Axial resolution is determined by:
SPL (medium and source) & PD
Axial resolution synonyms:
LARRD
Longitudinal Axial Range Radical Depth resolution
Is axial resolution adjustable?
No. SPL is fixed, therefor axial resolution is fixed.
Axial resolution typical values:
10 to 1.0 mm (Less is better)
Long SPL= _______ axial resolution
Bad
Short SPL= _______ axial resolution.
Good
Axial Resolution formula:
AR=SPL (mm)/2
Spatial pulse length formula:
Wavelength (mm) x # of cycles in pulse
Axial resolution in soft tissue formula:
AR (mm)=0.77 x # of cycles in pulse/Frequency (MHz)
What is determines by the pulse length?
Axial resolution
Two factors that help create short pulses:
Less ringing
Higher Frequency
What causes shorter pulses in a transducer because of less ringing?
Backing material
What creates short pulses because the wavelength is shorter?
Higher frequencies
When a pulse has fewer cycles in it, it is short and this is known as _________.
Less ringing
(AR)
Long pulse= _________=__________
More ringing
Poor axial resolution
(AR)
Short pulse= _________=___________
More ringing
Poor axial resolution
(AR)
Low frequency=____________=___________=__________
Long wavelength
Long pulse
Poor axial resolution
(AR)
High frequency= _________=__________=___________
Short wavelength
short pulse
Improved axial resolution
Better axial resolution is seen with:
Shorter SPL Shorter PD Higher frequencies (shorter wavelengths) Fewer cycles per pulse (less ringing) Lower numerical values
The amount of detail or accuracy when reflectors are perpendicular to the sound beam is _______
Lateral resolution
Lateral resolution units is ___
mm (any distance)
Lateral resolution is determined by:
Width of beam
Lateral resolution synonyms:
LATA
Lateral
Angular
Transverse
Azimuthal
Lateral resolution formula:
Lateral resolution (mm)=beam diameter (mm)
Higher frequencies will improve both ________ and ________ resolution
Axial
Lateral
(LR)
Higher frequency=______ pulse length =_________ axial resolution
Short
Better
(LR)
High frequency=_______ beam divergence=______ lateral resolution (in the far field)
Less
Better
Lateral resolution is best with _____
narrowest beam
Lateral resolution changes with ______, best at ______.
Depth
focus
Axial resolution is beast in the near field with __________ and best in the far field with _________
Shortest pulse
Shortest pulse
Lateral resolution is best in the near field with _________ and best in the far field with _______
Smallest diameter crystal
Largest diameter crystal
Three methods for focusing:
External
Internal
Phased array focusing
External focus is fixes which means ________.
It cannot be changed
External focusing is achieved by placing a ______ in front of the PZT crystal.
Curved lens
Internal focusing is fixed meaning that ______.
It cannot be changed
Internal focusing is achieved by creating a PZT crystal with a _______.
Curve
Electronic focus is ________, meaning that it can be changed.
Dynamic
Electronic focusing is only seen in transducers that have _______.
Multiple elements
Electronic focusing is achieved by __________.
Creating a delay in the excitation of each element.
What happens when a sound beam undergoes focusing?
Near zone diameter is less
The focus is closer to the transducer
More widening in the far field
The focal zone size is reduced
