# Module 4 : Resolution Flashcards

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1
Q

resolution

A
• most important thing to consider

- 3 aspects

2
Q

3 aspects of resolution

A
• detail (spatial)
• contrast
• temporal
3
Q

detailed resolution types

A
• axial (y)
• lateral (x)
• elevational (z)
4
Q

axial resolution

A
• ability to separate reflectors along the path of the beam

- dependant of the SPL and is calculated by 1/2 SPL

5
Q

axial resolution equation

A

AR = 1/2 SPL

SPL decreases axial resolution improves

6
Q

high frequency probes + axial

A
• increased frequency = decreased wavelength = decreased SPL = increased AR
7
Q

wide bandwidth + axial

A
• wider bandwidth = shorter pulse = increased AR
8
Q

decreased wavelength + axial

A
• decreased wavelength = decreased SPL = increased AR
9
Q

increased dampening + axial

A
• increased dampening = decreased RD = decreased SPL = increased AR
10
Q

low Q factor + axial

A
• lower Q = increased AR
11
Q

axial resolution names

A
```- LARD
\+ longitudinal
\+ axial
\+ range
\+ depth```
12
Q

lateral resolution

A
• ability to separate reflectors perpendicular to path of beam
• dependent on width of beam
• not constant with depth
13
Q

beam width and lateral resolution

A
• beam width decreases lateral resolution improves
14
Q

distance form probe + lateral

A
• beam shape changes with depth

- wider = worse lateral

15
Q

amount of focusing + lateral

A
• lateral resolution increases at the focus but worse everywhere else especially far field
16
Q

size of aperture + lateral

A
• shortens NZL so improves at focus but worse everywhere else
17
Q

NZL = lateral

A
• pushed deeper get better lateral resolution deeper
18
Q

higher frequency + lateral

A
• pushes near zone length deeper improving lateral resolution
19
Q

lateral resolution names

A
• LATA
• latera
• angular
• transverse
• azimuthal
20
Q

elevational resolution

A
• also known as slice thickness ability to separate reflectors perpendicular to image plane beam
• just like lateral resolution dependent on width of beam in Z axis
• fixed
• beam width in z axis decreases elevational resolution increases
21
Q

higher the frequency + elevational

A
• pushed near zone length not penetrating deeper but better resolution
22
Q

amount of focusing in z plane + elevational

A
• external mechanical focusing

- cannot be controlled but more focusing is better

23
Q

NZL + elevational plane

A
• longer = better

- shorter = worse

24
Q

distance from probe + elevational

A
• gets worse deeper without focusing
25
Q

contrast resolution

A
• ability to distinguish subtle differences in tissue gray scale
• related to bit depth
• higher bit depth more shade of gray more stuff to do with dynamic range
26
Q

temporal resolution

A
• ability to appreciate moving structures in real time
• related to frame rate
• frame rate increases temporal resolution increase
27
Q

temporal resolution formula

A

PRF = n x LPF x FR

```n = number of foci
LPF = lines per Frame
FR = frame rate```
28
Q

temporal resolution formula with penetration

A

penetration (cm) x n x LPF x FR
= 77000 cm/s
- 77000 used because it represents Hal the average speed of sound in soft tissue
- if you exceed this you get range ambiguity

29
Q

depth of penetration + temporal

A
• have to go deeper takes longer for it to come back = less FR = less TR
30
Q

number of foci + temporal

A
• hard to look at more than one thing
• have to add scan lines for every focus
• decrease FR = decrease TR
31
Q

sector width + temporal

A
• sector down = less lines per scan = less FR = less TR
32
Q

number of lines per frame

A
• increase lines per Frame = decrease FR = decrease TR

- want not a lot of interpolation

33
Q

frame rate + temporal

A
• increase FR = increase TR