Implementation of A Pulsed Wave Spectral Doppler on FPGA /
Moamen Ahmed Abu Bakr
- 2018
- 105 p. ill. 21 cm.
Supervisor: Ahmed G. Radwan
Thesis (M.A.)—Nile University, Egypt, 2018 .
"Includes bibliographical references"
Contents: Chapter 1 : Introduction ................................................................................................ 1 1.1 Research objectives............................................................................................ 2 1.2 Research organization ........................................................................................ 2 Chapter 2 : Background ................................................................................................ 3 2.1 Ultrasound historical background ...................................................................... 3 2.1.1 Progress of ultrasound through enabling technologies ............................... 3 2.1.2 Impact of advanced electronics on modern ultrasound .............................. 5 2.2 Medical ultrasound imaging .............................................................................. 8 2.2.1 Ultrasound waves ....................................................................................... 9 2.2.1.1 Frequency, speed, and wavelength ...................................................... 9 2.2.1.2 Pressure and intensity ........................................................................ 11 2.2.1.3 Reflection and scattering ................................................................... 12 2.2.1.4 Attenuation and absorption ............................................................... 14 2.2.2 System architecture .................................................................................. 15 2.2.2.1 Imaging modes .................................................................................. 16 2.2.2.2 Transducers ....................................................................................... 16 2.2.2.3 Front-end ........................................................................................... 19 2.2.2.3.1 Transmitters ..................................................................................... 19 2.2.2.3.2 Receivers ......................................................................................... 20 2.2.2.3.3 Array beamforming ......................................................................... 21 2.2.2.4 Back-End ........................................................................................... 23 Chapter 3 : Doppler Ultrasound Systems .................................................................. 27 3.1 Physical principles of Doppler ultrasound ....................................................... 27 3.2 Interaction between ultrasound and moving blood .......................................... 28 3.2.1 Blood flow ................................................................................................ 28 3.2.2 Scattering from blood ............................................................................... 28 VIII 3.3 Spectral Doppler systems ................................................................................ 30 3.3.1 Continuous wave systems ........................................................................ 30 3.3.2 Pulsed wave systems ................................................................................ 34 Chapter 4 : Design and Implementation .................................................................... 41 4.1 Recent trends in ultrasound systems architecture ........................................... 41 4.2 The DIGISON ultrasound system ................................................................... 43 4.2.1 Overview and main features .................................................................... 43 4.2.2 System architecture .................................................................................. 44 4.3 Design of the pulsed wave spectral Doppler module ...................................... 46 4.3.1 Introduction .............................................................................................. 46 4.3.2 Simulink reference model ........................................................................ 47 4.3.2.1 Model configuration and testing ....................................................... 48 4.3.2.1.1 RF data analysis .............................................................................. 49 4.3.2.1.2 Quadrature demodulator ................................................................. 50 4.3.2.1.3 Range gate integration .................................................................... 52 4.3.2.1.4 Wall filter ........................................................................................ 53 4.3.2.1.5 Spectrogram .................................................................................... 54 4.3.3 Hardware–Software partitioning .............................................................. 55 4.3.4 The switching mixer ................................................................................ 56 4.3.4.1 Comparing the two mixing methods ................................................ 56 4.3.4.2 Generating the mixing signals .......................................................... 57 4.3.4.3 Simulink model using the switching mixer ...................................... 58 4.4 Implementation on the FPGA ......................................................................... 60 4.4.1 Schematic of the Doppler module ............................................................ 61 4.4.2 Quadrature demodulator .......................................................................... 62 4.4.2.1 Mixer ................................................................................................ 62 4.4.2.2 Low pass filter .................................................................................. 64 4.4.3 Range gate integration ............................................................................. 66 4.4.3.1 Accumulator ..................................................................................... 66 4.4.3.2 Scaler ................................................................................................ 68 4.4.4 Design validation ..................................................................................... 69 4.4.5 System integration ................................................................................... 70 4.5 Experimental results ........................................................................................ 71 4.5.1 String phantom results ............................................................................. 71 4.5.2 In vivo results ........................................................................................... 73 IX Chapter 5 : Conclusions and Recommendations ....................................................... 75 5.1 Conclusion ....................................................................................................... 75 5.2 Recommendations for future research ............................................................. 76 References ...............
Abstract: Pulsed wave Doppler ultrasound is used today in the diagnosis of cardiovascular diseases and blood flow abnormalities. Doppler techniques have gained significance due to its safety, real-time performance and affordability. Most modern ultrasound systems have a Doppler mode. This work aims to develop a pulsed wave spectral Doppler module to be integrated into an ultrasound system. After reviewing the available algorithms and implementation techniques, a design was selected. Simulation models were built to test the design and identify the optimal implementation strategy. Building upon the models, the design was divided into a hardware part to be implemented on an FPGA and a software part that should run on a PC. The FPGA design was implemented in schematics and Verilog and simulated with real data. The design process was iterated and modifications were applied until satisfactory results have been achieved. The final design was integrated into an ultrasound system provided by IBE Technologies, Giza, Egypt. The software and the system integration were done in collaboration with the engineers at IBE Tech. and are not covered here. The developed module was tested using test equipment and in-vivo. The results of the testing procedures proved that the performance of the system is acceptable.