Comprehensive Ultrasound Research Platform Emma Muir Sam Muir Jacob Sandlund David Smith Advisor: Dr. José Sánchez

22 Outline Introduction Block Diagram Proposed System ◦ Functional Description ◦ Requirements Preliminary Work Equipment Schedule

33 Outline Introduction Block Diagram Proposed System ◦ Functional Description ◦ Requirements Preliminary Work Equipment Schedule

44 Ultrasound Introduction Medical Applications ◦ Detecting tumors and abnormalities Piezoelectric Transducer ◦ Pulse Excitation Changes in density reflect waves

55 Outline Introduction Block Diagram Proposed System ◦ Functional Description ◦ Requirements Preliminary Work Equipment Schedule

66 Block Diagram

77 Outline Introduction Block Diagram Proposed System ◦ Functional Description ◦ Requirements Preliminary Work Equipment Schedule

88 System Requirements Up to 8 transducer channels Excitation waveforms 3 μ s or less ◦ Time-bandwidth product of 40 Design for high frequency ◦ Signal to noise ratio (SNR) > 50 dB

99 Block Diagram

10 Waveform Generation Resolution Enhanced Compression Technique (REC) Pre-enhanced chirp calculated with convolution equivalence ◦ Increase Bandwidth (BW) of outputted signal ◦ Improves resolution

11 REC Technique h 1 (n) * c 1 (n) = h 2 (n) * c 2 (n) h 1 (n) = Transducer Impulse Response h 2 (n) = IR with increased BW c 2 (n) = Linear chirp c 1 (n) = Calculated pre-enhanced chirp

12 REC Requirement Enhance the bandwidth of the transducer to MHz ◦ Original bandwidth: 8.3 MHz ◦ Increase resolution

13 Block Diagram

14 Sigma Delta Modulation Analog to digital conversion technique 1-bit ADC Oversampling Quantization error compensation Signal values either 1 or -1 Sigma Delta Toolbox

15 Sigma Delta Modulation

16 Sigma Delta Modulation

17 Sigma Delta Modulation 10% mean squared error Chirp signal from 4MHz to 12MHz ◦ Based on REC signal Gsamples/second ◦ FPGA sampling rate = 1.06 Gsamples/second Oversampling Rate (OSR) = 512 ◦ T = 1 µs for testing, 3 µs for REC signal ◦ OSR must be a power of 2 ◦ GSamples/second = 2*OSR/T Divide Amplitude of signal by 2 ◦ Avoid overloading ◦ High OSR ◦ High order

18 Sigma Delta Modulation

19 Sigma Delta Modulation

20 Block Diagram

Why FPGA? Array, high speed ◦ 8-pins ◦ > 600 MHz Accurate, uninterrupted transmission Flexibility 21

22 FPGA Description Store waveform data ◦ Needs to be high speed ◦ Individual data for each pin Parallelize to pins High-speed transmission ◦ 1.07 GHz

23 FPGA Requirements Connect to PC ◦ 24 kbits Store on DDR2 ◦ 62.5 MHz required (266 MHz actual) ◦ At least 8 waveforms ◦ 3000 bits per waveform Each pin individualized (8 pins) ◦ Up to 5  s delays ◦ Different waveforms

24 FPGA (Pseudo) Flow Chart

25 FPGA Block Diagram

26 FPGA System

27 FPGA Transmission

28 FPGA to PC Communication UART ◦ baud Send waveform data Assign waveform to pins Assign delay to pins Start transmission

29 Block Diagram

30 High Voltage Amplifier Two parts ◦ Operational Amplifier ◦ H-bridge Op Amp ◦ Amplify the signal from the FPGA  -1 V to +1 V, or 0 V to 3.3 V  Amplify to 10 V  Needed for H-bridge  Slew Rate

31 High Voltage Amplifier H-bridge ◦ MOSFET configuration ◦ Will amplify from 10 V to ~100 V  100 V is a safe threshold for Ultrasound ◦ Must work at 1 Gsample/sec ◦ Output to ultrasonic transducer (or LPF)

32 Block Diagram

33 Low Pass Filter Convert the sigma delta signal to analog RC circuit will be used Bandpass nature of the source could be the filter ◦ More research needed 33

34 Block Diagram

35 Ultrasonic Transducer 128-channel linear array ◦ Will only be using 8 channels

36 Block Diagram

37 T/R Switch Protects analog front end from high voltages ◦ Clamps voltages so damage is avoided ◦ 1.9 V pp is specified ◦ TX810 by Texas Instruments

38 Printed Circuit Board Design ◦ Favor over perforated and bread board ◦ Six layers predicted because of frequencies  Eliminates cross-talk and EMI  More research is being done to predict layout of the board 38

39 Block Diagram

40 Analog Front End Two Parts ◦ Low Noise Amplifier (LNA) ◦ Analog-Digital Converter ◦ Using AD KITZ provided by Analog Devices  Contains both parts LNA ◦ Will amplify the received signal from the ultrasonic transducer ◦ Low amplitude from the transducer  High SNR 40

41 Analog Front End A-D ◦ Convert analog signal ◦ Will output digital signal to embedded device

42 Block Diagram

43 PC Data Processing

44 PC Data Processing

45 Pulse Compression Improve penetration depth and SNR Techniques ◦ Matched filter  Optimal for large amount of noise  Cross correlation  Creates side-lobes ◦ Inverse filter  Optimal for zero noise  Inaccurate for large amount of noise

46 Pulse Compression Wiener filter ◦ Balance between matched and inverse filters based on SNR ◦ Smoothing parameter  Can be used to optimize filter  Adjusts weighting of matched and inverse filter components

47 PC Data Processing

48 Beamforming Sensor 1 Sensor 2 Sensor 3 Sensor 4 Sensor 5 Sensor 6 Sensor 7 Sensor 8 Focus Distance (FD) Sensor Distance (SD)

49 Beamforming Delays based on Focus Distance (FD) and Sensor Distance (SD) ◦ ∆t1 = [(FD^2 + (½*SD)^2)^0.5 – FD]*(2/1540) ◦ ∆t2 = [(FD^2 + (1½*SD)^2)^0.5 – FD]*(2/1540) ◦ ∆t3 = [(FD^2 + (2½*SD)^2)^0.5 – FD]*(2/1540) ◦ ∆t4 = [(FD^2 + (3½*SD)^2)^0.5 – FD]*(2/1540) ◦ 1540 m/s is the speed of sound in tissue ◦ Multiply by 2 to account for distance travelled in both directions

50 Beamforming Sensor 1 Sensor 8 Sensor 2 Sensor 7 Sensor 3 Sensor 6 Sensor 4 Sensor 5 Sum Delay ∆t4 - ∆t3 Sum Output Delay ∆t4 - ∆t2 Delay ∆t4 - ∆t1

51 PC Data Processing

52 Time-Gain Compensation Compensates for attenuation of the received signal Attenuation of the sound waves is caused by the depth of the echoing substance More depth = More attenuation

53 PC Data Processing

54 Envelope Detection Determines the bounds of the processed signal Detected width contains the display information about the tested tissue Hilbert transform

55 PC Data Processing

56 Log Compression Convert the data from linear values to dB values 20*log 10 (Current Value) Creates clearer images

57 PC Data Processing

58 Graphical User Interface (GUI) Displays image result of signal processing Allows user to enter contrast Allows user to select depth

59 Current Displayed Image | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 0.25cm10cm20cm30cm Depth Contrast | Max Update Graphical User Interface (GUI)

60 Functional Requirements ◦ All data processing shall be performed in less than 2 minutes. ◦ The image created will display an image for depths between 0.25 cm and 30 cm. Graphical User Interface (GUI)

61 Outline Introduction Block Diagram Proposed System ◦ Functional Description ◦ Requirements Preliminary Work Equipment Schedule

62 Block Diagram

63 Sigma Delta Modulation 44 th Order Equiripple Filter without Gain Compensation

64 Sigma Delta Modulation 44 th Order Equiripple Filter with Linear Gain Compensation

65 Sigma Delta Modulation RC (R=330 Ω, C=10 pF) Filter without Gain Compensation

66 Sigma Delta Modulation RC (R=330 Ω, C=10pF) Filter with Linear Gain Compensation

67 Sigma Delta Modulation Cross Correlation and Mean Square Error FilterCross CorrelationMean Square Error Equiripple filter without Gain Compensation Equiripple filter with Linear Gain Compensation RC without Gain Compensation RC with Linear Gain Compensation

68 Block Diagram

69 PC Data Processing

70 PC Data Processing Array of points in Fields II Distance in mm 100 Transducer

71 Beamforming Distance in mm

72 Time-Gain Compensation Distance in mm

73 Envelope Detection Distance in mm

74 Log Compression Distance in mm

75 Log Compression

76 Graphical User Interface (GUI) Distance in mm

77 | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 0.25cm10cm20cm30cm Depth Contrast | Max Update Graphical User Interface (GUI)

78 Block Diagram

79 REC Preliminary Results MATLAB simulation Increased bandwidth of transducer to 150% of original bandwidth Linear chirp frequencies in the range of 1.14 times the bandwidth ◦ Optimal number to reduce side-lobes during pulse compression Resulting chirp can be applied to finished system

80 h 1 (n) * c 1 (n) = h 2 (n) * c 2 (n)

81

82 Block Diagram

83 PC Data Processing

84 Pulse Compression Results MATLAB simulation Wiener filter SNR of 60 dB Input is REC pre-enhanced chirp

85

86 Block Diagram

87 FPGA Preliminary Work Interface to DDR2 System to arbitrate access Multi-pin high-speed output ◦ Verified at lower frequencies Separate data, delays for pins UART works alone, needs integration

88 Block Diagram

89 Analog Preliminary Work H-bridge ◦ V DD = 15 V; V DS = 10 V; V GS = 5 V;  V d = 5 V; ◦ Datasheet at those values: I d  0.3 A,  R d  20 . ◦ P Rd = (0.3 A) 2 x (  ) = 1.5 W. ◦ High for resistors used

90 Analog Preliminary Work MOSFET circuit used:

91 Analog Preliminary Work H-bridge device cannot function at high enough frequencies Decided to build own H-bridge

92 Block Diagram

93 Analog Preliminary Work Simulation circuit for T/R Switch ◦ Spice model provided by T.I.

94 Simulated waveforms Simulated at V in = 10V. V outpp = 1.85V 1.9V 

95 Simulated waveforms Simulated at Vin = 90V. V outpp = 1.94V Includes overshoot. 1.9V 

96 Printed Circuit Board Design changes (i.e. H-bridge), so board changes Still no connector for the transducer Using OrCAD PCB Designer ◦ Book provided to assist with design IC footprint troubles 96

97 Equipment LeCroy High Speed Oscilloscope 725Zi Blatek 128 pin Ultrasound Probe Ultrasound Testing Phantom Xilinx Virtex 5 Development Kit ML509 UART Null Modem Adapter Analog Devices Analog Front End AD KITZ – Low noise amplifier – Variable control amplifier – ADC MOSFETS x4 for the H-Bridge – model to be determined PCB x2 Texas Instruments –T/R Switch TX810 Software – Matlab Version R2007b – Sigma Delta Toolbox – Field II – Agilent Connection Expert – Xilinx Hydrophone

98 Schedule

99 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 ( REC) Dr. Irwin Dr. Lu Mr. Mattus Mr. Schmidt

100 References [1] J. A. Zagzebski, Essentials of Ultrasound Physics, St. Louis, MO: Mosby, [2] R. Schreier and G. C. Temes. Understanding Delta-Sigma Data Converters, John Wiley & Sons, Inc., [3] R. Schreier, The Delta-Sigma Toolbox Version 7.3. Analog Devices, Inc, [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 , Feb [5] M. Oelze. “Bandwidth and Resolution Enhancement Through Pulse Compression,” IEEE Trans. Ultrason., Ferroelectr. Freq. Contr., vol. 54, no. 4, pp , Apr [6] Mitzner, Kraig. Complete PCB Design Using OrCad Capture and PCB Editor, Newnes, 2009.

101 References Cont. [7] Montrose, Mark I. Printed Circuit Board Design Techniques For EMC Compliance: A Handbook for Designers, Wiley-IEEE Press, [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 , Volume 34, Supplement 1, Part 1, [9] 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 , 1992.

102 Questions?