Comprehensive Ultrasound Research Platform

1
Comprehensive Ultrasound Research Platform

• Emma Muir
• Sam Muir
• Jacob Sandlund
• David Smith
• Advisor Dr. Sánchez
• Co-advisor Dr. Irwin

2
Outline

• Introduction
• System
• Block Diagram / Functional Description
• Requirements
• Progress

2
3
Outline

• Introduction
• System
• Block Diagram / Functional Description
• Requirements
• Progress

3
3
4
Ultrasound Introduction

• Piezoelectric Transducer
• Pulse Excitation
• Changes in density reflect waves

4
5
Objective

• Create an Ultrasound Research Platform
• Image Creation
• Multi-pin
• Beamforming
• Sigma Delta Architecture
• 1-bit ADC
• Arbitrary Waveforms
• Coded excitation signals
• Configurable delays

5
5
6
Motivation

• Improve Ultrasound Techniques
• Medical Applications
• Detecting tumors and abnormalities
• Future Research

6
6
7
Significance

• Test codes (arbitrary) for better imaging
• Multi-pin to allow Beamforming
• Architecture reduces cost and size
• RASMUS
• Two 19 inch racks
• Sigma Delta vs. 12 bit DAC

7
7
8
Outline

• Introduction
• System
• Block Diagram / Functional Description
• Requirements
• Progress

8
8
9
Block Diagram
9
10
PC Data Processing
10
11
Outline

• Introduction
• System
• Block Diagram / Functional Description
• Requirements
• Progress

11
11
12
System Requirements

• Up to 8 transducer channels
• Excitations lt 3 µs
• Time-bandwidth product of 40
• High frequency design
• Signal to noise ratio (SNR) gt 50 dB

12
13
Sigma Delta Modulation

• lt 10 MSE
• 500 M samples/second
• Trade off
• Accuracy vs. Stability
• OSR 16 (must be a power of 2)
• Order 2nd

14
FPGA Requirements

• Store data on DDR2
• 62.5 MHz
• 8 waveforms
• 1536 bits per waveform
• Output Data
• 8 Individualized Pins
• Delays of up to 5 ms
• 500 MHz

14
15
FPGA to PC Communication

• UART
• 115200 baud
• Send waveform data
• Assign waveform to pins
• Assign delay to pins
• Start transmission

15
16
Graphical User Interface (GUI)

• Data Processing
• Less than 2 minutes
• Display an image
• Depths between 0.25 cm and 30 cm.
• Adjust contrast

16
17
Outline

• Introduction
• System
• Block Diagram / Functional Description
• Requirements
• Progress

17
17
18
Progress
18
18
19
Progress
19
19
20
Amplifier Progress

• Different designs examined
• H-Bridge
• 2 MOSFETs
• Push-pull RF MOSFET
• 1 MOSFET
• N-channel RF MOSFET
• Final Design

20
20
21
Amplifier Progress

• Discuss problems/solutions

22
Amplifier Progress
23
Amplifier Progress
24
Amplifier Progress
25
Amplifier Progress
26
Amplifier Progress
27
T/R Switch Progress
28
T/R Switch Progress
1.92V
29
PCB Progress

• Footprints
• TX810
• Transmit/ReceiveSwitch
• RF MOSFET
• Set INTO board

30
Progress
30
30
31
Progress
31
31
32
Progress
32
32
33
FPGA Progress

• Arbitrary transmission
• Output verified
• 500 MHz
• Multi-pin
• Currently 4
• Adjustable
• Arbitrary length
• Must be 256 bit pieces
• Adjustable delays of lt 33 ms

33
33
34
FPGA Flowchart Progress
34
34
35
FPGA Remaining

• Fix storing waveform data from UART
• Inconsistent results
• Increase delays precision
• After data retrieved
• Make output more exact
• Change to 8 pins

35
35
36
Progress
36
36
37
UART Progress

• UART
• 115200 baud works
• PC to FPGA Communication
• Start transmission signal
• Set waveforms to pins
• Set delays for pins
• Waveform data
• Inconsistent

37
37
38
38
38
39
Waveform GUI Features

• Multiple selection
• Automatic pin settings removal
• Save/Load settings
• Check files exist when loading settings
• Let None represent an array of 0s

39
40
Progress
40
40
41
FPGA Results
Delayed
Voltage
Time (s)
Cross-talk
Cross-talk
Voltage
Time (s)
41
41
42
FPGA Results
Normalized Correlation
Max Corr. 0.97
Sample number
42
42
43
FPGA Results
43
43
44
FPGA Results
44
44
45
FPGA Results
45
45
46
Progress
46
46
47
Analog Front End Results
Source Analog Devices UG-016 http//www.analog.co
m/static/imported-files/user_guides/UG-016.pdf
47
47
48
Alternatives

• Analog Front End
• 12 bit resolution
• 80 MSPS
• Lecroy High Speed Oscilloscope
• 725Zi
• 8 bit Resolution
• 20 GSPS
• 4 Channels

48
48
49
Progress
49
49
50
Progress
50
50
51
Beamforming
Sensors
Focal Point
Point
Delay based on distance from point to sensor and
distance from sensor to focal point Note No
delay at the Focal Point
51
52
Without Beamforming
With Beamforming
53
Attenuation

• Average frequency attenuation in tissue
• 0.5 dB/cm/MHz
• 5e-5 dB/m/Hz
• Doubled for ultrasound imaging
• Frequency 8MHz
• Maximum depth 30cm
• Maximum attenuation 240dB
• Image dB range 0dB to -50dB

54
Time Gain Compensation

• Based on depth of point in image
• Att 1dB/cm/MHz
• TGC AttDepth8MHz
• Add to compensate
• Note that this increases white noise for larger
  depths

54
55
Progress
55
55
56
Sigma Delta Representation
56
57
Without Pre-Enhanced Magnitude
Correlation 0.9763
57
58
Pre-Enhanced Magnitude
58
59
With Pre-Enhanced Magnitude
Correlation 0.9916
59
60
Sigma Delta Features

• Easy to modify
• Frequency
• Period
• Waveform equation
• Number of samples
• Pre-Enhanced Magnitude
• Checks/displays correlation
• Writes output to a file as 0s and 1s

60
61
Sigma Delta Additions

• GUI interface for entering
• Frequency
• Period
• Waveform equation
• Select location to save file
• Interface with Waveform GUI

61
62
REC Results

• MATLAB simulation
• 150 of original bandwidth
• Linear chirp frequencies
• 1.14 times the bandwidth
• Reduce side-lobes during pulse compression
• Apply to finished system

62
63

• h1(n) c1(n) h2(n) c2(n)

63
64
64
65
Pulse Compression Results

• MATLAB simulation
• Wiener filter
• SNR of 60 dB
• Input is REC pre-enhanced chirp
• Varied Smoothing Factor (SF)
• Operating Point

65
66
66
67
Field II Simulations
REC Excitation and Pulse Compression SF 0.1
Impulse Excitation
67
67
68
Progress
68
68
69
MATLAB GUI Features

• Depth from 2mm to 231mm
• Max dB range from 10dB to 60dB
• Update chart settings automatically
• Update data in 54s

69
70
MATLAB GUI
71
MATLAB GUI
72
MATLAB GUI Additions

• Depth from 2mm to 300mm
• Restrict max dB to 40dB to 60dB
• Allow user to type value or scroll
• Minimize update time
• Convert to C

72
73
Progress
73
73
74
Progress
74
74
75
Progress
75
75
76
Additional Information

• Visit http//cegt201.bradley.edu/projects/
• proj2011/ultra/index.html

77
Acknowledgments

• The authors would like to thank Analog Devices
  and Texas instruments for their donation of
  parts.
• This work is partially supported by a grant from
  Bradley University (13 26 154 REC)
• Dr. Irwin
• Dr. Lu
• Mr. Mattus
• Mr. Schmitt
• Andy Fouts

77
78
References

• 1 J. A. Zagzebski, Essentials of Ultrasound
  Physics, St. Louis, MO Mosby, 1996.
• 2 R. Schreier and G. C. Temes. Understanding
  Delta-Sigma Data Converters, John
• Wiley Sons, Inc., 2005.
• 3 R. Schreier, The Delta-Sigma Toolbox Version
  7.3. Analog Devices, Inc, 2009.
• 4 T. Misaridis and J. A. Jensen. Use of
  Modulated Excitation Signals in
• Medical Ultrasound, IEEE Trans. Ultrason.,
  Ferroelectr. Freq. Contr., vol. 52, no. 2,
• pp. 177-191, Feb. 2005.
• 5 M. Oelze. Bandwidth and Resolution
  Enhancement
• Through Pulse Compression, IEEE Trans.
  Ultrason., Ferroelectr. Freq. Contr., vol. 54,
• no. 4, pp. 768-781, Apr. 2007.
• 6 Mitzner, Kraig. Complete PCB Design Using
  OrCad Capture and PCB Editor,
• Newnes, 2009.

78
79
References Cont.

• 7 Montrose, Mark I. Printed Circuit Board
  Design Techniques For EMC Compliance
• A Handbook for Designers, Wiley-IEEE Press, 2000.
• 8 J.A. Jensen. Field A Program for Simulating
  Ultrasound Systems, Paper presented
• at the 10th Nordic-Baltic Conference on
  Biomedical Imaging Published in Medical
• Biological Engineering Computing, pp. 351-353,
  Volume 34, Supplement 1, Part 1,
• 1996.
• 9 Kai E. Thomenius. Evolution of Ultrasound
  Beamformers, IEEE Trans. Ultrason.,
• Ferroelectr. Freq. Contr., pp. 1615-1622, 1996.
• 10 J.A. Jensen and N. B. Svendsen. Calculation
  of pressure fields from arbitrarily
• shaped, apodized, and excited ultrasound
  transducers, IEEE Trans. Ultrason.,
• Ferroelec., Freq. Contr., 39, pp. 262-267, 1992.
• 11 Kjærgaard, Nina. "RASMUS." Center for Fast
  Ultrasound Imaging. Technical
• University of Denmark, 28 Sept. 2010. Web. 25
  Feb. 2011.
• lthttp//www.dtu.dk/centre/cfu/English/research/fac
  ilities/RASMUS.aspxgt.

79
80
Questions?
80
81
Without TGC
With TGC
81
82
Using Delta as the Excitation Signal
Using REC (chirp)