Presenter Tony Podkowa November 13 2012 Advisor Dr José R Sánchez Department of Electrical and Computer Engineering Outline I Introduction II Project Summary III Block Diagram ID: 760424
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Slide1
Ultrasound Simulations using REC and SAFT
Presenter
:
Tony
Podkowa
November 13, 2012
Advisor: Dr José R.
Sánchez
Department
of Electrical
and Computer Engineering
Slide2Outline
I. IntroductionII. Project SummaryIII. Block DiagramIV. Preliminary WorkV. Schedule
2
Slide3Outline
I. IntroductionII. Project SummaryIII. Block DiagramIV. Preliminary WorkV. Schedule
3
Slide4Introduction
Medical ApplicationsTumor detectionBlood flow imagingCardiac imagingPiezoelectric TransducerUltrasonic PulsesTissue Density reflects Pulses
4
Slide5Outline
I. IntroductionII. Project SummaryIII. Block DiagramIV. Preliminary WorkV. Schedule
5
Slide6Project Summary
Specialized techniques improve image resolution and SNR.Resolution Enhancement Compression (REC)Improves Axial Resolution and SNRSynthetic Aperture Focusing Techniques (SAFT)Improve Lateral Resolution and SNRGoal: To simulate the combination of both REC and SAFT in an ultrasound system using the Matlab addon Field II.
6
Slide7Outline
I. IntroductionII. Project SummaryIII. Block DiagramIV. Preliminary WorkV. Schedule
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Slide8System
Block Diagram
REC
Transducer
SAFT
V
in
(t)
V
pc
(t)
Image
Recon.
Image Output
V
l
c
(t)
Received
Echo Signals
Beamformed
Signals
8
Slide9Resolution Enhancement Compression
Pulse Compression TechniqueUses Convolution EquivalenceExchange the transducer impulse response a desired responseIncreases bandwidthBetter resolution
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Slide10Source:
M
. Oelze, “Bandwidth and Resolution Enhancement through Pulse Compression,” IEEE Trans. Ultrason., Ferroelec. and Freq. Control, vol. 54, pp. 768–781, Apr. 2007.
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Slide11REC Subsystem
Waveform
Generator
V
ulc
(f)
V
pc
(f)
Tukey
Window
V
lc
(f)
V
upc
(f)
11
Slide12System
Block Diagram
REC
Transducer
SAFT
V
in
(t)
V
pc
(t)
Image
Recon.
Image Output
V
l
c
(t)
Received
Echo Signals
Beamformed
Signals
12
Slide13Transducer
Linear Array Transducer consisting of several elementsCapable of emitting and receiving ultrasonic pulsesGenerates several signals to be processed to form an image.
S. I.
Nikolov, Synthetic Aperture Tissue and Flow Ultrasound Imaging. PhD thesis, Technical University of Denmark, Aug. 2001.
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Slide14Transducer Specifications
256 Elements3 MHz Center Frequency200 MHz Sampling Frequency4 mm Element Height0.26 mm Element Width0.04 mm Element Kerf20 mm Focus
Height
Width
Kerf
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Slide15System
Block Diagram
REC
Transducer
SAFT
Received
Echo Signals
V
in
(t)
V
pc
(t)
Image
Recon.
Beamformed
Signals
Image Output
V
l
c
(t)
15
Slide16Synthetic Aperture Focusing Techniques
Electrically focuses signals to create an artificial aperture.Uses different excitation schemesThree Variations:Generic Synthetic Aperture Ultrasound (GSAU)Synthetic Transmit Aperture Ultrasound (STAU)Synthetic Receive Aperture Ultrasound (SRAU)Results generated by delay and sum beamforming.
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Slide17GSAU
Transmit with one and receive with one.Each transmit event generates a low resolution image.Information needs to be delayed appropriately for each pixel before summing.Gain in SNR:
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Slide18STAU
Transmit with one and receive with all.Additional degree of freedomGain in SNR:
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Slide19SRAU
Transmit with all and receive with one.Gain in SNR:
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Slide20SAFT
Delay and Sum
Beamforming
Apodization
Image Scan Lines
Received
Echo Signals
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Slide21Apodization
Spatial WindowingUsed to shape the beam profileReweighting by apodization coefficients Several different windowing techniques can be studiedRectangularTriangularRaised Cosine
a1
a2
aN
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Slide22System
Block Diagram
REC
Transducer
SAFT
Received
Echo Signals
V
in
(t)
V
pc
(t)
Image
Recon.
Beamformed
Signals
Image Output
V
l
c
(t)
22
Slide23Image Reconstruction Subsystem
Wiener
Filter
Envelope
Detection
Logarithmic
Compression
Limiter
Beamformed
Signal
Image Scan Line
V
l
c
(t)
23
Slide24Outline
I. IntroductionII. Project SummaryIII. Block DiagramIV. Preliminary WorkV. Schedule
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Slide25Preliminary Work
Image Reconstruction subsystem completed.STAU partially completedConventional pulsing instead of RECIndividual low resolution images generated.Output image generated.Rectangular apodization64 elements instead of 256
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Slide26Individual STAU Images
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Slide27Effect of Beamforming
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Slide28Outline
I. IntroductionII. Project SummaryIII. Block DiagramIV. Preliminary WorkV. Schedule
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Slide29Schedule
1/28 – 2/8: REC2/11 – 2/22: GPGPU implementation of STAU2/25 – 3/8: GSAU 3/11 – 3/29: SRAU4/1 – 4/12: Prepare for Student Scholarship Expo4/15 – 4/19: Expo4/22 – 5/3: Write Final Report & Presentation
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Slide30Ultrasound Simulations using REC and SAFT
Presenter
:
Tony
Podkowa
November 13, 2012
Advisor: Dr José R.
Sánchez
Department
of Electrical
and Computer Engineering
Slide31Generic Synthetic Aperture Ultrasound
Object
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Slide32Generic Synthetic Aperture Ultrasound
Object
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Slide33Matched Filter
ADC
Pre-
amplifier
Matchedfilter
Echo Signal
SAFT
A
Reconstructed image
A
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