Download - Ultrasound Principle 超音波原理
Propagated
wave
Refracted
wave
Refracted
waveReflected
wave
Reflected
wave
Medium #1 Medium #2
折射與反射
• Power … watt
• Intensity… watt / cm2
– Loudness or strength
• Decibel notation …dB = 10 log 10 ( ----- )
I
I0
dB Intensity Ratio Amplitude Ratio
70 10,000,000 10,00060 1,000,000 1,00050 100,000 32040 10,000 10030 1,000 3220 100 1010 10 3.2 0 1 1-10 0.1 0.32-20 0.01 0.1
Power and Intensity
Gain
結果 : 超音波頻率提升 ,穿透力卻下降
Reflection
Absorption
Scattering
Frequency Penetration
Frequency Vs Penetration 頻率與穿透力的關係
ResolutionElevation
Axis
Lateral
Spatial ResolutionSpatial Resolution
Frequency
Transmit
Signal process
Focusing Steering Channel ….
Acoustic lance
Matching Layer
CrystalAbsorbing material
Resolution
Contrast ResolutionContrast Resolution
Compress
Compress
ExpandSoft Tissue
Strongreflection
Weakreflection
Acoustic Signal
Visual light
Dynamic Range
Beamfomer
一條音束從發射到接收要花多少時間?Suppose depth = 16 cm , sound speed 1540 m/s16 x 2 / 1540 2 / 10000 second
一個 frame 0.025 second要花 30 ~ 40 Hz
1231211st Frame
2nd Frame 123121
VariableGain Stage
ImageProcessingMemory
ScanConverter
SignalProcessing
Display
Xducer
Receiver
Xmitter
GainTGCLGC
B/WContrast
Color/HuePost-processColorizationAnnotation
Measurement
LoopQuick review
Mode control2D, B (Sector,Linear, convex)MDopplerColorAQ
Image Format ZoomImage & B/W InvertDual Image
Pre-processingCompressionPersistence
Xmit FocusDepth
Frequency
Signal process
Post-processing Curves
Post-processing
Gray Level before Post-processing Curves
Gra
y L
evel
aft
er P
ost
-pro
cess
ing C
urves
Input level
Output level
Post-processing:,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
Tissue Boundary, Thrombus等.會更加明顯而獲致最佳解像度
B ModeColorFlow
Image Doppler
Spectrum
AnatomyAnatomy
FunctionFunction
ViabilityViability
InformationInformationManagementManagement