Ultrasound Principle
超音波原理
Diagnosis Imaging System
影像診斷系統
Sound wave
Pressure
maximum
Wavelength
波長 λ
振幅
Amplitude
Pressure
minimum
1 Cycle
週期
1 Cycle
週期
1 Cycle
週期
Sound wave
• Amplitude
• Frequency
• Velocity
dB
MHz 1,000,000 次/秒
1540 m/s in body
折射與反射
Refracted
Reflected
wave
wave
Propagated
wave
Medium #1
Medium #2
Power and Intensity
• Power … watt
• Intensity… watt / cm2
– Loudness or
strength
• Decibel notation …
I
dB = 10 log 10 ( ----- )
I0
Gain
dB
70
60
50
40
30
20
10
0
-10
-20
Intensity Ratio
10,000,000
1,000,000
100,000
10,000
1,000
100
10
1
0.1
0.01
Amplitude Ratio
10,000
1,000
320
100
32
10
3.2
1
0.32
0.1
Frequency Vs Penetration
頻率與穿透力的關係
Reflection
Frequency Absorption
Penetration
Scattering
結果: 超音波頻率提升,穿透力卻下降
Frequency Vs Resolution
頻率與解像度的關係
Higher Frequency
Reflect
can
smaller objects
超音波頻率提升解像度也會提升
Resolution
Spatial
Resolution
Elevation
Acoustic lance
Matching Layer
Crystal
Absorbing material
Axis
Lateral
Frequency
Transmit
Signal process
Focusing
Steering
Channel
….
Resolution
Contrast Resolution
Strong
reflection
Soft Tissue
Weak
reflection
Acoustic Signal
Compress
Dynamic
Expand
Range
Compress
Visual light
Beamfomer
Transducer
Beamfomer
121
1st Frame
2nd Frame 121
3
3
1
2
2
1
s
/
m
0
4
5
1
d
e
e
p
d
s
n
o
dc
n
e
u
s
o
s
0
0
0
,0
1
m/
c
62
1
=
0
h4
t
5
p
1
e
d
/
e2
s
o
x
p
p
6
u
1
S
一條音束從發射到接收要花多少時間？
要花 0.025 second
z
H
0
4
~
0
3
e
m
a
r
f
一個
Signal process
Receiver
Variable
Signal
Gain Stage Processing
Scan
Converter
Memory
Image
Processing
Display
Xducer
Xmitter
Xmit Focus
Depth
Frequency
Gain
TGC
LGC
B/W
Pre-processing
Loop
Contrast
Compression
Quick review
Color/Hue
Persistence Mode control
Post-process
2D, B (Sector,Linear, convex)
M
Doppler
Color
AQ
Image Format
Zoom
Image & B/W Invert
Dual Image
Colorization
Annotation
Measurement
P o st-p r o c e ssin g
P o st-p r o c e ssin g C u r v e s
Gray Level after Post-processing Curves
O u tp u t le v e l
P o st-p r o c e ssin g :
藉 由 特 殊 電 腦 影 像 處 理 ,改 變 不
同 組 織 的 相 對 灰 度 顯 示 ,例 如
T issu e B o u n d a r y , T h r o m b u s等
會更加明顯而獲致最佳解像度.
In p u t le v e l
G r a y L e v e l b e fo r e P o st-p r o c e ssin g C u r v e s
Anatomy
Information
Management
B Mode
Color
Flow
Image
Function
Doppler
Viability Spectrum
Signal process / Control
TGC
Dynamic
Range
Focus
Depth
Gain