1
Q
-front t back, parallel to sound beam
-determined by SPL
-same at all depths, does not change
-best with short pulses, less cycles, high frequency
-LAARD
longitudinal, axial,radial,depth
A
axial resolution
2
Q
- Side by side, perpendicular to beam
- Determined by beam width
- Best with narrowest beams
- Changes w/ Depth
- LATA – Lateral, angular, transverse, azimuthal
- Large Beam diameter , High Frequency – LESS divergence in far field
A
Lateral resolution
3
Q
Determined by
thickness of PZT
propagation speed of PZT
A
Pulsed transducers
4
Q
Thinner PZT
A
High frequency
5
Q
Thick PZT
A
Low frequency
6
Q
1/2 wavelength thick
A
PZT
7
Q
1/4 wavelength thick
A
Matching layer
8
Q
increases efficiency of sound transmission w/ impedance between skin & active element
A
Matching layer
9
Q
Reduces ringing, shortens pulse duration & SPL
A
Damping material
10
Q
Maximum Frequency - Minimum frequency equals ?
A
Bandwidth
11
Q
- Pulses w/ short duration
- uses backing material
- reduced sensitivity
- wide bandwidth
- Low Q factor
- Improved axial resolution
A
Imaging transducer
12
Q
- Continous wave
- no backing material
- increased sensitive
- narrow bandwidth
- high Q factor
- no image
A
Non - imaging transducer
13
Q
- Small diameter
- lower frequency
- more divergence
A
Shallow focus
14
Q
- large diameter
- higher frequency
- less divergence
A
Deep focus ( better lateral resolution in far field)
15
Q
Determined by frame rate
A
Temporal resolution
16
Q
Frame is determined by
A
Image depth # of pulses , focus, sector size, line density
17
Q
Short go return time
Short Tframe
Higher frame rate
superior temporal resolution
A
Shallow imaging
18
Q
Long go return time
Longer Frame
Low frame rate
Inferior temporal resolution
A
Deep imaging
19
Q
Single focus
Narrow setor
Low line density
More pulses per frame
A
SUPERIOR TEMP RESOLUTION
20
Q
High line density improves
A
Spatial resolution
21
Q
Uses old data post processing larger pixel size same # of pixels as the original ROI unchanged temporal resolution
A
Read magnification
22
Q
Aquires new data preprocessing smaller pixel size more pixels than original ROI improved spatial resolution May improve temporal resolution
A
Write magnification
23
Q
Improves higher signal to noise ration
improved axial, spatial, contrast resolution
-deeper penetration
A
Coded excitation does this
24
Q
A Mode
X -
Y -
A
X - depth
Y - amplitude
25
B Mode
X -
Y -
x - depth
| z - amplitude
26
M - Mode
X - Time
| Y - depth
27
first function of receiver take each signal and make them equally larger
Treats all signals the same
Amplification (receiver gain)
28
Second function of receiver is to correct for attenuation by creating an image uniformly bright from top to bottom. Signals treated differently
Compensation (TGC, DGC)
29
Gray scale mapping
max compression - high contrast , narrow dynamic range (black & white)
min compression - low contrast, wide dyanmic range
Compression (log compression, dynamic range)
30
Fourth function of receiver two part process that changes electrical signals within the receiver into a form for suitable CRT display
Demodulation
31
Two forms or demodulation
Rectifaction
| Smoothing enveloping
32
Converting all negative voltage into positive voltages
Rectification
33
Eliminate small bumps in voltage signals
Smoothing enveloping
34
5th function Allow us to choose whether or not to dimply low level signals (gray scale info) strong signals remain unchanged
Reject (threshold suppression)
35
- Changes brightness of entire image
- alters signal to nosie ratio
- alters patient exposure
- has bio effect concert
Output power
36
- change brightness of entire image
- does not affect signal to noise
- does not change patients exposure
- no bio effect concerns
Receiver gain
37
If image is to dark
Increase receiver gain
38
If image is to bright
reduce output power
39
Image element
Image detail
Spatial resolution
All pertain to pixels
40
Computer memory
Gray shades
Contrast resolution
All pertain to bits
41
Maintains & organizes system timing
Master synchronizer
42
Converts electrical sdingals
Transducer
43
determines PRP, PRF & amplitude along with firing patterns
Pulser
44
Produces pictures to display
Receiver
45
CRT/ Television
Display
46
Archive
Storage
47
Created in tissue from non-linear behavior
Harmonics
48
Created during reflection
contrast harmonics
49
Created during transmission
Tissue harmonics
50
Fills in missin data, imrpoves spatial resolution
Fill-interpolation
51
For phases transducers only, frames are averages & improves signal to noise ratio, reduces artifact , improves station resolution, reduces temporal resolution
Spatial compounding
52
Advanced tecnquie that reduces speckle & noise , reflect signal is divided into subabnds of limited frequencies & an image is created from each sub band. Image from sub band combines into a single image
Frequency compounding
53
Image processing technique the continues to display information from older images then a smoother image with reduced noise, higher signal to noise ratio & improved image quality is produced
Temporal compounding (persistence)
54
Venous flow
Phasic flow
55
Cardiac contraction
Pulsatile
56
Constant speed, venous circulation
Steady flow
57
2 x velocity x transducer frequency x cos 0 / propagation speed
Doppler shift equation
58
0 or 180
Most accurate doppler shift
59
Clinically best
60
60
90
no measurement
61
Advantage - measure high velocities
| Disadvantage - range ambiguity , lack of TGC
CW (non imaging) - no damping)
62
advantage - range resolution
disadvantage - inaccurate measurement of high velocities
aliasing can occur
Pulsed wave (uses damping)
63
1. adjust scale
2. low frequency
3. shallow sample volume
4. use cw transducer
5. adjust baseline
Eliminate aliasing
64
Greater accuracy sensitive to low flow
| disadvantage - more time to get imp, frame rate, and tamp resolution reduced
Packet/ ensemle length
65
multiple equally spaced, parraell to sound beam, deeper & along straight line
reverberation
66
single, solid hyper echoic line
comet tail/ ring down
67
structure above has high attenuation, shadow color same as background color, absence of true anatomy below
shadowing
68
refraction @ edge of circular structure, hypo due to refraction and beam spreading
edge shadowing
69
opposite of shadow, structure below has low attenuation, hyperechoic, parallel to sound beam
enhancement
70
ide by side form of enhancement, hyperechoic, high intensity in focal zone
Focal enhancement/ banding
71
– 2nd copy of reflector, artifact is DEEPER then real & equal distance from mirror
Mirror image
72
correct number of reflectors at improper depth, faster than soft tissue – shallow reflector, slower than soft tissue – deeper
Prop speed
73
obliquely 2nd copy of true reflector & media have different propagation speeds, appear side by side cannot tell which one is real & degrades lateral resolution
Refraction
74
- ONLY with mechincal single crystal transducer, 2nd copy of true reflector placed side by side
Side lobes
75
only with array transducers, 2nd copy of true reflector , side by side
Grating lobes
76
elevational resolution, beam has greater width than reflector, fill in anechoic structures also called partial volume artifact/ curried with a 1 ½ dimensional array transducer. Linear array = poor
slice thickness
77
Grainy appearance from interference effects of scattered sound
Speckle
78
late reflections appear to shallow on image, cured by a LOWER PRF. (incorrect depth)
Range ambiguity
79
reflector place incorrectly on display
Multipath
80
strategic pins located @ speed of soft tissue. Tests lateral & axial resolution. Cannot evaluate gray scale (no attenuation)
AIUM 100 mm test object
81
– pins mimic cysts & solid masses, has attenuation can evaluate gray scale
Tissue equivalent phantom
82
100 W/cm ^2
unfocused
83
1 w/cm^2
focused
84
measures acoustic output of transducer
Hydrophone
85
measures beam profiles from interactions of sound waves and light
Acoustic optics
86
– transducer turns acoustic energy into heat calculating total power
calorimeter
87
measures specific points in space and change in temp
Thermocouple
88
science to identify & measure characteristics of US relevant to potential bioeffects
Dosimetery
89
dynamic technique that produces images from sound reflections based on differing stiffness
Elastography
SPI REVIEW
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