1. Ultrasound Simulations using REC and SAFT Presenter: Tony Podkowa November 13, 2012 Advisor: Dr José R. Sánchez Department of Electrical and Computer Engineering

2. Outline I. Introduction II.Project Summary III.Block Diagram IV.Preliminary Work V.Schedule 2

3. Outline I. Introduction II.Project Summary III.Block Diagram IV.Preliminary Work V.Schedule 3

4. Introduction Medical Applications Medical Applications Tumor detection Tumor detection Blood flow imaging Blood flow imaging Cardiac imaging Cardiac imaging Piezoelectric Transducer Piezoelectric Transducer Ultrasonic Pulses Ultrasonic Pulses Tissue Density reflects Pulses Tissue Density reflects Pulses 4

5. Outline I. Introduction II.Project Summary III.Block Diagram IV.Preliminary Work V.Schedule 5

6. Project Summary Specialized techniques improve image resolution and SNR. Specialized techniques improve image resolution and SNR. Resolution Enhancement Compression (REC) Resolution Enhancement Compression (REC) Improves Axial Resolution and SNR Improves Axial Resolution and SNR Synthetic Aperture Focusing Techniques (SAFT) Synthetic Aperture Focusing Techniques (SAFT) Improve Lateral Resolution and SNR 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

7. Outline I. Introduction II.Project Summary III.Block Diagram IV.Preliminary Work V.Schedule 7

8. System Block Diagram REC TransducerSAFT V in (t) V pc (t) Image Recon. Image Output V lc (t) Received Echo Signals Beamformed Signals 8

9. Resolution Enhancement Compression Pulse Compression Technique Pulse Compression Technique Uses Convolution Equivalence Uses Convolution Equivalence Exchange the transducer impulse response a desired response Exchange the transducer impulse response a desired response Increases bandwidth Increases bandwidth Better resolution Better resolution 9

10. Source: M. Oelze, “Bandwidth and Resolution Enhancement through Pulse Compression,” IEEE Trans. Ultrason., Ferroelec. and Freq. Control, vol. 54, pp. 768–781, Apr. 2007. 10

11. REC Subsystem Waveform Generator V ulc (f) V pc (f) Tukey Window V lc (f) V upc (f) 11

12. System Block Diagram REC TransducerSAFT V in (t) V pc (t) Image Recon. Image Output V lc (t) Received Echo Signals Beamformed Signals 12

13. Transducer Linear Array Transducer consisting of several elements Linear Array Transducer consisting of several elements Capable of emitting and receiving ultrasonic pulses Capable of emitting and receiving ultrasonic pulses Generates several signals to be processed to form an image. Generates 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. 13

14. Transducer Specifications 256 Elements 256 Elements 3 MHz Center Frequency 3 MHz Center Frequency 200 MHz Sampling Frequency 200 MHz Sampling Frequency 4 mm Element Height 4 mm Element Height 0.26 mm Element Width 0.26 mm Element Width 0.04 mm Element Kerf 0.04 mm Element Kerf 20 mm Focus 20 mm Focus Height Width Kerf 14

15. System Block Diagram REC TransducerSAFT Received Echo Signals V in (t) V pc (t) Image Recon. Beamformed Signals Image Output V lc (t) 15

16. Synthetic Aperture Focusing Techniques Electrically focuses signals to create an artificial aperture. Electrically focuses signals to create an artificial aperture. Uses different excitation schemes Uses different excitation schemes Three Variations: Three Variations: Generic Synthetic Aperture Ultrasound (GSAU) Generic Synthetic Aperture Ultrasound (GSAU) Synthetic Transmit Aperture Ultrasound (STAU) Synthetic Transmit Aperture Ultrasound (STAU) Synthetic Receive Aperture Ultrasound (SRAU) Synthetic Receive Aperture Ultrasound (SRAU) Results generated by delay and sum beamforming. Results generated by delay and sum beamforming. 16

17. GSAU Transmit with one and receive with one. Transmit with one and receive with one. Each transmit event generates a low resolution image. Each transmit event generates a low resolution image. Information needs to be delayed appropriately for each pixel before summing. Information needs to be delayed appropriately for each pixel before summing. Gain in SNR: Gain in SNR: 17

18. STAU Transmit with one and receive with all. Transmit with one and receive with all. Additional degree of freedom Additional degree of freedom Gain in SNR: Gain in SNR: 18

19. SRAU Transmit with all and receive with one. Transmit with all and receive with one. Gain in SNR: Gain in SNR: 19

20. SAFT Delay and Sum Beamforming Apodization Image Scan Lines Received Echo Signals 20

21. Apodization Spatial Windowing Spatial Windowing Used to shape the beam profile Used to shape the beam profile Reweighting by apodization coefficients Reweighting by apodization coefficients Several different windowing techniques can be studied Several different windowing techniques can be studied Rectangular Rectangular Triangular Triangular Raised Cosine Raised Cosine a1a1 a2a2 aNaN 21

22. System Block Diagram REC TransducerSAFT Received Echo Signals V in (t) V pc (t) Image Recon. Beamformed Signals Image Output V lc (t) 22

23. Image Reconstruction Subsystem Wiener Filter Envelope Detection Logarithmic Compression Limiter Beamformed Signal Image Scan Line V lc (t) 23

24. Outline I. Introduction II.Project Summary III.Block Diagram IV.Preliminary Work V.Schedule 24

25. Preliminary Work Image Reconstruction subsystem completed. Image Reconstruction subsystem completed. STAU partially completed STAU partially completed Conventional pulsing instead of REC Conventional pulsing instead of REC Individual low resolution images generated. Individual low resolution images generated. Output image generated. Output image generated. Rectangular apodization Rectangular apodization 64 elements instead of 256 64 elements instead of 256 25

26. Individual STAU Images 26

27. Effect of Beamforming 27

28. Outline I. Introduction II.Project Summary III.Block Diagram IV.Preliminary Work V.Schedule 28

29. Schedule 1/28 – 2/8: REC 1/28 – 2/8: REC 2/11 – 2/22: GPGPU implementation of STAU 2/11 – 2/22: GPGPU implementation of STAU 2/25 – 3/8: GSAU 2/25 – 3/8: GSAU 3/11 – 3/29: SRAU 3/11 – 3/29: SRAU 4/1 – 4/12: Prepare for Student Scholarship Expo 4/1 – 4/12: Prepare for Student Scholarship Expo 4/15 – 4/19: Expo 4/15 – 4/19: Expo 4/22 – 5/3: Write Final Report & Presentation 4/22 – 5/3: Write Final Report & Presentation 29

30. Ultrasound Simulations using REC and SAFT Presenter: Tony Podkowa November 13, 2012 Advisor: Dr José R. Sánchez Department of Electrical and Computer Engineering

31. Generic Synthetic Aperture Ultrasound Object 31

32. Generic Synthetic Aperture Ultrasound Object 32

33. Matched Filter ADC Pre- amplifier Matched filter Echo Signal SAFT A Reconstructed image A 33