Physics 2 - Module 4 & 5 Flashcards
The number of times the sweep of sound is produced by the transducer
Frame rate (frames per second)
How is frame rate related to temporal resolution?
Directly related. If frame rate increases, so does temporal resolution.
What are the 4 factors that affect frame rate?
- Depth
- Sector angle
- Number of scan lines
- Number of focal zones
How does depth affect frame rate?
Increased depth, decreased FR
How does sector width affect FR?
Narrower sector, increased FR
How does # of scan lines affect FR?
More scan lines = lower FR
How long does it take sound to travel 1 cm and back?
13 microseconds
Each element is divided into smaller pieces or sub-elements that act as one crystal and causes grating lobes to project out at 90 degrees or greater to the main beam
Sub dicing
What are the 3 kinds of resolution
- Detail (spatial)
- Contrast
- Temporal
What are the 3 types of detail resolution
- Axial
- Lateral
- Elevational
The ability to separate reflectors along the path of the beam
Axial resolution
What is axial resolution dependent on?
SPL
=1/2 SPL
If SPL decreases, what happens to axial resolution?
It improves
what 5 things relate to better axial resolution?
- Higher frequency
- Wide bandwidths
- Decreased wavelength
- Increased damping
- Low Q factor
The ability to separate reflectors perpendicular to the path of the beam.
Lateral resolution
What is lateral resolution dependent on?
The width of the beam.
What are other names for axial resolution?
- Longitudinal
- Range
- Depth
What happens to resolution if beam width decreases?
It improves
What 5 things relate to better lateral resolution?
- Distance from the probe
- Higher frequency
- Amount of focusing
- NZL
- Size of aperture
What are some other names for lateral resolution?
- Angular
- Transverse
- Azimuthal
The ability to separate reflectors perpendicular to the image plane of the beam
Elevational resolution/slice thickness
What is elevational resolution directly related to?
Width of the beam in the z axis
What 4 things relate to better elevational resolution?
- Distance from the probe
- Higher frequency
- NZL
- Amount of focusing in the Z plane
The ability to distinguish subtle differences in tissue grayscale
Contrast resolution
What is contrast resolution related to?
Bit depth
What things relate to better temporal resolution? 5 of them:
- Depth
- Sector width
- Number of foci
- Frame rate
- Number of lines per frame
