Educational Course - Imaging Ultrasound I J. Brian Fowlkes, PhD* University of Michigan Department of Radiology and Biomedical Engineering *Equipment support from GE Medical and Toshiba Medical [email protected]Triplex Mode Gas Molecules in a Sound Wave λ - Spatial f - Temporal Wave Propagation Animation from Dr. Dan Russell, Kettering University Relationships Velocity-Frequency-Wavelength c = Sound Velocity f = Frequency λ = Wavelength c = f λ Speed of Sound c (m/s)
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Educational Course - Imaging Ultrasound I Triplex Mode
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Educational Course - Imaging Ultrasound I
J. Brian Fowlkes, PhD* University of Michigan
Department of Radiology and Biomedical Engineering
*Equipment support from GE Medical and Toshiba Medical [email protected]
Triplex Mode
Gas Molecules in a Sound Wave
λ - Spatial f - Temporal
Wave Propagation
Animation from Dr. Dan Russell, Kettering University"
Relationships Velocity-Frequency-Wavelength
c = Sound Velocity"f = Frequency"λ = Wavelength"
c = f λ
Speed of Sound
c (m/s)
Refraction"c2 < c1"
Propagation
Reflection"
Reflection and Refraction
θi = θr "
sin θi/ sin θt = c1/c2 (Snellʼs Law)"
Reflection and Transmission • The reflection coefficient is
R = [(Z2-Z1)/(Z2+Z1)]2
• The transmission coefficient is
T = (4Z2Z1)/(Z2+Z1)2
where Z1 and Z2 are the impedances of the two media.
Specular Reflection Noise or Structure?"
Speckle"
Electronic"
Speckle
Scatter dia << λ"
λ
Image Statistics
SNR=I/σ"
CNR=(Io−Ib)/(σo2+σb
2)1/2"
where averages are taken "over an ROI"
Attenuation (from Absorption and Scatter)
I = Ioe-2µd"
Depth"d"
Inte
nsity"
ATTENUATION COEFFICIENT
7.5 2.5 5.0
Lateral Resolution"Approximately equal to the beamwidth W"
W"
φ If φ < 50ο"Wf = λF/D""= λ(F#)"
D"
F"
I/Q Data
• Baseband result for a specified carrier frequency
• I - In phase
• Q - quadrature (shifted 900)
I = A(t)cos(ωt)cos(ω0t)
Q = A(t)cos(ωt)sin(ω0t)
€
BB = I + jQ€
I = (A(t) /2)[cos(ωt +ω0t) + cos(ωt −ω0t)]
€
Q = (A(t) /2)[sin(ωt +ω0t) + sin(ωt −ω0t)]
Env = I2 +Q2
RF Data
RF Data
-20000
-15000
-10000
-5000
0
5000
10000
15000
20000
0 2 4 6 8 10 12 14 16 18 20
Time (microsec)
Am
plit
ude
(a.u
.)
Series1
A-mode
Phased Array Beam Steering
Transducer
Traditional B-mode Imaging
Transducer
Compound Imaging
Compound Imaging
Speckle Reduction"
Compound Imaging
Normal B-Mode
Example in Breast Imaging Wave Fronts
Animation courtesy of Dr. Dan Russell, Kettering University"
Power Pulse Inversion Assume breathing motion of 2 cm/s This is 20 um per firing, ie. 4.8° phase shift @ 1 MHz
5°
10°
_
+
+
+
5°
5°
Echo 1"
Echo 2"
Echo 3"2X"
Microvascular Imaging
Source: M Bruce, M Averkiou, K Tiemann, S Lohmaier, J Powers, K Beach "Vascular flow and perfusion imaging with ultrasound contrast agents” Ultrasound in Med. & Biol., Vol. 30, No. 6, pp. 735–743, 2004
1800"3600"
Microvascular Imaging
Source: M Bruce, M Averkiou, K Tiemann, S Lohmaier, J Powers, K Beach "Vascular flow and perfusion imaging with ultrasound contrast agents” Ultrasound in Med. & Biol., Vol. 30, No. 6, pp. 735–743, 2004
• Hemangioma. Both images with ultrasound contrast agent. (A) conventional imaging (B) Pulse inversion imaging (a)
Source: (a) Averkiou M., Powers J., Skyba D., Bruce M., and Jensen S. "Ultrasound Contrast Imaging Research. " Ultrasound Quarterly Vol. 19, No. 1, pp. 27-37 (2003)
One at a Time, Please
Source: Fuminori Moriyasu, M.D., Ph.D., Department of Gastroenterology & Hepatology, Tokyo Medical University, Japan"
Hold It!!!
Source: Fuminori Moriyasu, M.D., Ph.D., Department of Gastroenterology & Hepatology, Tokyo Medical University, Japan"