PVDF Sensor Design and FPGA Implementation of Ultrasound Power Measurement

PVDF Sensor Design and FPGA Implementation of Ultrasound Power

Measurement

Imamul Muttakin, Nur Sabrina Risman, Rania Mahfooz, Dr Hau Yuan Wen, Prof Ir Dr Eko Supriyanto, Dr Nazrul Anuar Nayan, Dr Rosmina Jaafar

Universiti Kebangsaan Malaysia, 43600 UKM Bangi, Selangor, Malaysia

Universiti Teknologi Malaysia, UTM Skudai, 81300 Johor, Malaysia

Outline

• Introduction • Objective• Ultrasound Power Meter System Architecture• Simulations and Discussions• Conclusions

Outline 2

Introduction

Ultrasound machines

•Widely industrial and medical technology.

•Application in diagnostic and therapeutic uses.

•For diagnostic purpose, ultrasound is safe, painless, method in examining the internals organs that avoids the use of radiation.

•While, therapeutic were starting to emerge almost five decades ago, such as the ability of tissue heating up to some centimetres under the skin.

Introduction 3

Introduction

Introduction 4

Ultrasound Power Meter

•Is a device that measure and calibrate the output power and intensity of an ultrasound machine•Safety awareness•Avoid unwanted power exposure to the patient•International Electro-technical Commission (IEC) in 1960•Most of the current ultrasound power meters are cost expensive, less portability and limited for either high power therapeutic or low power diagnostic purpose.

• designed for optimum Ultrasound power capturing the Ultrasound machine, minimize interference effect and noise, as well as stabilize mechanical construction of sensor.

• The advantages of PVDF are ; Low acoustic impedance that closely matches to the human tissues,

water and other organic materials. High output voltage and dielectric strength compare with other piezo

materials. Moist resisting. Can be fabricated into unusual designs.

Introduction 5

Polyvinylidene Fluoride (PVDF) polymer sensor

• An integrated circuit (IC) that can be programmed in the field after manufacture

• Provides a versatile and cost effective platform in designing system with shorter design cycle.

• High speed, reconfigurability, cost effective and better quality of medical instrumentation.

Introduction 6

Field Programmable Gate Array (FPGA)

Digital signal Processing (DSP)

High sampling rate

Lack of Input-output (I/O) ports

Microcontroller

Low sampling rate

Limited Input-output (I/O) ports

Objective

• To design an in-house ultrasound power measurement system that should provide the features of compact and simple in construction, able to provide a reliable power measurement results, and user friendly.

Objective 7

Ultrasound Power Meter System Architecture

Ultrasound power meter system architecture 8

Figure 1. System architecture of ultrasound power meter.

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SUB-SYSTEM FUNCTIONALITY

Signal Acquisition Unit (PVDF Sensor) The simulated sensor provided 2.5 MHzto 8.5 MHz responses with amplitude ofaround 4 Vpp.

Analog Conditional Circuit To filter, amplify and convert continuous analog signal to discrete digital number.

Digital Processing Unit To measure ultrasound power based on ITA is temporal-average intensity (mW/cm2).

Display Unit To display power measurement on LCD

Table 1. Functionality of each Sub-system

Ultrasound power meter system architecture

Simulation and Discussions

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Input ports 12-bit PVDF sensor signal

Output ports LCD

Frequency range 0.5 MHz – 10 MHz

Intensity range 1 mW/cm2 to 10 W/cm2

Table 2 summarizes the overall system performance and design specification of the proposed ultrasound power meter.

Simulation and discussions

Tools Software : Quartus II, Nios II IDEHardware : Altera DE2 BoardLanguage : Verilog HDL and C++


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• The ultrasound power measurement system hardware prototyping on Altera Cyclone II DE2 board.

• The FPGA clock able to capture at maximum 10 MHz full form of ultrasound signal.

• Therefore, the FPGA clock must reach the maximum frequency at 21.32 MHz in order to make good sampling of ultrasound signal.

• 5 V peak is chosen for voltage work level.

Figure 2. Hardware prototyping of ultrasound power meter



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Figure 3. The Simulation for overall system


Input of ultrasound signal from two sensors are illustrated by datain1 and datain2.

The rom_dataout produced by the internal module inside the test bench in which digitized ultrasound signal from data converter simulation.

From the simulation, dataout shows after 80 ns.

The result identifies the ultrasound power meter is functionally correct according in the equation of Temporal-average intensity, ITA below.

where N is number of sampling, V(i,x)2 is sensor’s output voltage dependant on temperature and distance, M(f)2 is sensitivity of sensor, is density of medium, and c is speed of sound in the medium. Arithmetic operations in a linear equation such as addition, multiplication, division and power are involved

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Product / Features


UPM-DT-100AV. (Ohmic

Instrument Co.)

Ultrasound Watt Meter UPM

2000 (Netech Biomedical &

Industrial Test Instruments)


– UPM – 30 (Ohm

Instrument Co.)

Proposed Work

Measurement range 0 W to 30 W 0.1 W to 30 W 0 W to 30 W 1 W/cm2 to 50 W/cm2

Frequency range 0.5 MHz to 10 MHz 0.5 MHz to 10 MHz 0.5 MHz to 10 MHz 0.5 MHz to 10 MHz

Ultrasound test media Degassed water Degassed water Degassed water Normal water or

ultrasound gel

Resolution 200mW 0.1 W 150m W 0.003 mW/cm2

Power source 12 VAC,500 mA power

adapter

9 V - 15V

Sensor - - - PVDF

Ultrasound Applications - - - Diagnostic and

therapeutics

Display 3-Digit LCD LCD - LCD

Communication

Interface

RS-232 RS-232 RS-232 USB

Table 3. Comparison of This proposed work with other product.


Conclusion

• This paper has presented an in-house ultrasound power measurement system with a low cost, user friendly and high precision capability suitable for medical application.

• The unique design has been obtained while the test results show a possibility to use it for an ultrasound intensity measurement purpose.

• In future for further modification towards an ultrasound, digital processing unit is desired to improve the overall system performance. Hence support the real time analysis and optimizing hardware area (e.g. reducing logic element).

Conclusion15

Thank You

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PVDF Sensor Design and FPGA Implementation of Ultrasound Power Measurement

Engineering

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