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Development of a Portable Ultrasound Imaging System with Wireless Patient Monitor
Won Seuk Jang
The Graduate School
Yonsei University
Graduate Program of Biomedical Engineering
Development of a Portable Ultrasound Imaging System with Wireless Patient Monitor
A DissertationSubmitted to the Graduate Program of Biomedical Engineering
and the Graduate School of Yonsei Universityin partial fulfillment of the
requirements for the degree of Doctor of Philosophy
Won Seuk Jang
August 2010
This certifies that the dissertation of Won Seuk Jang is approved.
___________________________
Thesis Supervisor: Nam Hyun Kim
___________________________
Thesis Committee Member: Nam Sik Chung
___________________________
Thesis Committee Member: Jin Bae Park
___________________________
Thesis Committee Member: Ha Suk Bae
___________________________
Thesis Committee Member: Sung Min Kim
The Graduate School
Yonsei University
August 2010
감사의 글
본 논문이 완성되기까지 항상 세심한 지도와 아낌없는 배려로 가르침을 주신
김남현 교수님께 존경과 깊은 감사를 드립니다. 논문 심사위원으로서 아낌없는
조언을 주신 정남식 교수님, 박진배 교수님, 배하석 교수님 그리고 김성민 교수님께
진심으로 감사드립니다. 그리고, 학부시절부터 항상 자상한 충고와 아낌없는 학문의
가르침을 주신 윤형로 교수님과 윤영로 교수님께도 존경과 감사를 드립니다. 또한,
항상 많은 관심을 주신 의학공학교실의 김덕원 교수님과 유선국 교수님께
감사드리며, 의공학과의 이경중 교수님, 김동윤 교수님과 김영호 교수님께도
감사드립니다.
항상 애정 어린 사랑으로 격려해 주신 한국보건산업진흥원 이경민 단장님,
바이메드시스템(주) 박종백 부사장님, (주)케이티메드 허재만 박사님께 깊이
감사드립니다. 논문작성에 아낌없는 지원을 해주신 서강대학교 송태경 교수님,
경북대학교 노용래 교수님, (주)바이오넷 강동주 사장님과 계상범 수석님께 진심으로
감사드리며, 논문작성에 도움을 준 전대근 박사님, 김응석 박사님, 이광재, 양희림에게
감사의 마음을 표합니다. 의학공학교실의 연구실 후배로서 부족한 선배에게 큰 힘이
되어준 김종옥, 김지훈, 장혜정, 안서영, 전소혜에게 감사함을 표하며
생체신호처리연구실의 차동익 박사님, 김원식 박사님, 성홍모 박사님, 신재우 박사,
장승진 박사, 설아람 박사, 이우희 선배님, 최혜원, 강병윤, 김성윤, 이정훈과 여러
선후배님들에게도 고마움을 표합니다. 학부시절부터 지금까지 항상 곁에서 많은
도움을 준 김동석 팀장과 남기창 박사에게 진심으로 고마움을 표하며 장성윤, 박동현,
이세진, 이희종, 고동훈, 박성제 그 외 동기들에게도 감사의 마음을 전합니다. 항상
깊은 우정을 나눈 권오학, 김계하, 송윤승에게 감사의 마음을 표하여 사랑이 가득하길
바랍니다. 항상 따뜻하고 자상하신 마음으로 걱정해 주시고 응원을 해주신
장인어른과 장모님, 항상 믿음과 사랑으로 대해 주신 처남내외와 처제에게 감사의
마음을 전하며, 처조카인 성열이와 승은이도 건강하고 큰 꿈을 키워 가기를 바랍니다.
어려운 상황임에도 불구하고 도움을 준 누님께 감사하며 조카인 성현이가 큰 꿈을
이루기를 바라며, 멀리 카자흐스탄에서 버팀목이 되어 주는 형님과 형수님께 감사의
마음을 전하며 조카인 유나와 예나가 건강하고 큰 꿈을 이루어 가기를 바랍니다.
지금까지도 헌신적인 사랑으로 걱정하여 주시고 손녀들을 챙겨주시느라 고생하시는
어머니께 무한한 감사의 마음을 전합니다. 매사에 사려 깊고 믿음직한 첫째 다연이,
넘치는 재치로 가족에게 웃음을 주는 둘째 혜원이, 가득한 애교로 가족에게 새로운
행복을 주고 있는 셋째 지민이, 항상 곁에서 기쁨과 어려움을 함께 하고 용기와
희망을 준 나의 사랑하는 아내 선미와 본 결실의 기쁨을 함께 하고자 합니다.
2010년 8월
장 원 석 올림
- i -
CONTENTS
List of Figures --------------------------------------------- iii
List of Tables --------------------------------------------- vi
Abstract -------------------------------------------------- vii
Chapter 1. Introduction -------------------------------------- 1
Chapter 2. Portable Ultrasound Imaging Device -------------------- 5
2.1. Imaging algorithm for portable ultrasound imaging device ------------ 5
2.1.1. Periodic sparse array -------------------------------- 6
2.1.2. Extended aperture ----------------------------------- 8
2.2. System structure of the portable ultrasound imaging device --------- 10
2.3. Power supply for portable ultrasound imaging device ---------- 14
2.4. Ultrasound smart probe ---------------------------------- 16
2.4.1. Wireless smart probe --------------------------------- 17
2.4.2. Design ultrasound smart array and performance evaluation --- 19
2.4.3. Manufacturing of the ultrasound smart probe -------------- 26
2.5. Portable ultrasound imaging device based on embedded PC ---------- 27
Chapter 3. Wireless Bio-Signal Measurement Module --------------- 31
3.1. ECG design ------------------------------------------- 34
3.2. SpO2 design ------------------------------------------- 48
3.3. NIBP design ------------------------------------------ 52
3.4. Temperature design ------------------------------------ 55
3.5. Wireless interface of bio-signal measurement module ------------ 58
3.6. Integrated wireless bio-signal measurement module ----------- 62
- ii -
Chapter 4. System integration --------------------------------- 63
4.1. GUI ------------------------------------------------- 64
4.2. Integrated portable diagnosis system ----------------------- 70
Chapter 5. Result ------------------------------------------- 71
Chapter 6. Conclusion --------------------------------------- 78
References ------------------------------------------------ 81
국문요약 --------------------------------------------------- 85
- iii -
LIST OF FIGURES
Fig. 1 Example of the sparse and combination array --------------- 6
Fig. 2 General model of the periodic sparse array ----------------- 7
Fig. 3 Images using periodic sparse array ----------------------- 7
Fig. 4 Examples of the extended array -------------------------- 9
Fig. 5 (a)General image (b)Image using extended aperture ----------- 9
Fig. 6 Block diagram of the portable ultrasound imaging device ------ 11
Fig. 7 Block diagram of the echo processor ---------------------- 12
Fig. 8 Block diagram of the digital scan-line converter ------------- 13
Fig. 9 Power circuit and battery ------------------------------- 15
Fig. 10 System structure of the smart probe --------------------- 17
Fig. 11 Developed 64 channels smart probe ---------------------- 17
Fig. 12 Block diagram for wireless smart probe ------------------ 18
Fig. 13 Wireless smart probe --------------------------------- 18
Fig 14. Basic structure of the ultrasound array ------------------- 19
Fig. 15 Finite element analysis model and field analysis ------------ 20
Fig. 16 Result of the simulation -------------------------------- 20
Fig. 17 Result of ultrasound field analysis ----------------------- 21
Fig. 18 Result of the manufactured smart array pulse-echo test ------ 23
Fig. 19 Result of the measurement for beam characteristics
in ultrasound smart array ------------------------------ 24
Fig. 20 Result of impedance measurement of the smart probe ------- 25
Fig. 21 Developed ultrasound smart probe ----------------------- 26
Fig. 22 System structure of the portable ultrasound imaging device --- 27
Fig. 23 Block diagram of Rx/Tx of the ultrasound and beamformer circuit --- 28
- iv -
Fig. 24 Connection of the smart probe, Rx/Tx and beamformer ------ 28
Fig. 25 Back-end of the ultrasound and embedded system board ----- 29
Fig. 26 Integrated portable ultrasound imaging device -------------- 30
Fig. 27 Revised portable ultrasound imaging device ---------------- 30
Fig. 28 Block diagram for wireless bio-signal measurement module --- 30
Fig. 29 Main processing diagram of the system ------------------- 32
Fig. 30 Overall structure of the main software -------------------- 33
Fig. 31 Block diagram of ECG hardware ------------------------- 35
Fig. 32 Developed ECG board --------------------------------- 36
Fig. 33 Softwate flow of the ECG ------------------------------ 37
Fig. 34 The flow of QRS complex detection algorithm -------------- 39
Fig. 35 QRS Detection of Arrhythmia --------------------------- 44
Fig. 36 QRS detection in case of not using the pacer pulse
detection at pacer pulse and QRS complex ----------------- 46
Fig. 37 QRS detection in case of using the pacer pulse detection
at pacer pulse and QRS complex ------------------------ 46
Fig. 38 System diagram of SpO2 ----------------------------- 49
Fig. 39 (a) Circuit of SpO2 (b) Board of SpO2 -------------------- 50
Fig. 40 Software flow of SpO2 -------------------------------- 51
Fig. 41 Block diagram of the non-invasive blood pressure ---------- 52
Fig. 42 (a) Circuit of the NIBP (b) Board of NIBP ---------------- 53
Fig. 43 Software flow of the non-invasive blood pressure ----------- 54
Fig. 44 System diagram of the temperature ---------------------- 55
Fig. 45 (a) Circuit of temperature (b) Board of temperature --------- 56
- v -
Fig. 46 Software flow of the temperature ------------------------ 57
Fig. 47 BM-310 bluetooth chip -------------------------------- 58
Fig. 48 Block diagram for BM-310 module chip ------------------- 60
Fig. 49 Block diagram of UART between BM-310 module and MCU ----- 60
Fig. 50 Wireless bluetooth communication circuit ------------------ 61
Fig. 51 Wireless bluetooth communication board ------------------- 61
Fig. 52 Integrated wireless bio-signal measurement module --------- 62
Fig. 53 Basic concept of integrated portable diagnosis system ------- 63
Fig. 54 Basic design of display -------------------------------- 64
Fig. 55 Dispaly of the menu ---------------------------------- 65
Fig. 56 Display part of bio-signal ------------------------------ 67
Fig. 57 Display part of ultrasound image ------------------------ 68
Fig. 58 Display overlapped ultrasound image and bio-signal --------- 68
Fig. 59 Portable ultrasound imaging device combined with
wireless bio-signal measurement module ------------------ 70
Fig. 60. Comparison of image of developed 32-channel system
and commercialized 64-channel system ------------------ 72
Fig. 61 Image comparative evaluation of the commercialized 64-channel
system and the developed system ----------------------- 74
Fig. 62 Image comparative evaluation of the commercialized 64-channel
system and the developed system ----------------------- 74
Fig. 63 Color flow image from the developed system -------------- 76
Fig. 64 Data viewer of the server in the hospital ----------------- 77
- vi -
LIST OF TABLES
Table 1 Power management mode of developed system ------------ 14
Table 2 Structural variables of the ultrasound array and result of the design --- 21
Table 3 Result of the characteristic measurement about 10 yield array --- 22
Table 4 Performance improvement of the developed hardware system --- 35
Table 5 The result of detection performance according to size and
width of QRS complex ---------------------------------- 42
Table 6 The result of QRS complex detection according to
baseline change ------------------------------------- 43
Table 7 Results of QRS complex detection performance of the arrhythmia ---- 45
Table 8 The result of pacer pulse detection performance
at pacer pulse and QRS complex ----------------------- 47
Table 9 Comparison image quality between developed 32-channel
system and commercialized 64 channel system ------------ 75
- vii -
ABSTRACT
Development of a portable ultrasound
imaging system with wireless patient monitor
Won Seuk Jang
Graduate Program in
Biomedical Engineering
Yonsei University
With recent improvement on standards of living and advancement of medical
and science technology, development and manufacture of u-healthcare system for
diagnosis at remote places other than hospitals such as home, offices and
emergency areas are on the boil. U-healthcare system developed in this study will
receive bio-signals and ultrasound images of the patient from various remote sites
other than hospitals and use the data to provide high quality medical services. In
this study, we have developed ultrasound imaging based portable compact
diagnosis system which is connected with a wireless bio-signal module to be used
at various environment such as emergency medical sites, etc. For this, a compact
ultrasound imaging device, a smart probe and a wireless bio-signal module have
been developed and integrated. Small channel/high resolution ultrasound image
algorithm, such as periodic sparse array method and extended aperture method,
has been realized to make a compact ultrasound imaging device. Also the size of
the ultrasound imaging device has been minimized by integrating a beamformer
- viii -
processor and an efficient back-end processor into one FPGA. Especially the
developed beamformer can process 32 channels with one chip, including TxPG and
quadrature demodulation as well as the RxBF and also a hardware that has been
realized with extended aperture method has been inserted into a smart probe to
minimize the size of the ultrasound imaging device. And a power with battery
which is re-chargeable has also been developed with the basic premise that the
u-healthcare should be portable.
Bio-signal module that can measure and send the ECG, SpO2, blood pressure
and temperature wirelessly to the ultrasound imaging device has been developed.
And the server/client system of the hospital receiving, storing or re-sending the
data from the ultrasound imaging device has been realized. The exterior has been
designed considering the user's portability and convenience and these details have
been combined into developing u-healthcare system. Developed u-healthcare
system not only improves the bio-signal and ultrasound imaging technology for
patient-focused diagnostics but also provides opportunity to improve application
technology for emergency medical, overall improvement of ultrasound imaging
device and an innovative industrial competitiveness internationally. U-healthcare
system developed through this study is a new product combining imaging devices
and bio-signal module and will introduce a new place to the market with material
contribution to national economic growth.
Key words : u-healthcare, ultrasound imaging, bio-signal, ECG, smart probe
- 1 -
CHAPTER 1
Introduction
With higher standards of living and advanced medical services in recent years,
more people are interested in enjoying advantages of healthcare, good environment
and social welfare. Untiring needs for high quality medical services and notable
increase of social recognition and requirement for improvement of readiness to the
emergency situations and emergency delivery system both for civilians and
militaries have been enhancing the demand for telemedicine and home-healthcare
system which would allow people to be diagnosed at home, workplace, emergency
site or outdoor as well as in hospital[1, 2, 3]. While portable diagnosis system
plays an important role in checking patient's status in emergency situations, being
recognized as a material equipment in public healthcare services, its capacity is
very limited to certain particular areas such as bio-signal measurement or in-vitro
diagnostic[4, 5]. To provide services equivalent to those of hospitals, telemedicine
or home-healthcare system should carry out multi-diagnosis device functions
which would present bio-signals and various medical image information. To
diagnose patients without any restrictions of time and place and to exchange
clinical treatment related information for patients between emergency site and
hospitals or medical experts in real time, miniaturization of portable diagnosis
device and medical information technology managing patients’ information as
coupled with hospital information system (HIS) together with the wired/wireless
communication channel are essential.
It was the Pentagon to which the portable imaging diagnosis system was first
introduced. Telemedicine had also contributed to lower the mortality rate down to
- 2 -
3 percent in 1992 Gulf War. Among 5 projects carried out by Pentagon Defense
Advanced Research Project Agency to provide medical treatment to the patient
through telemedicine during the wartime, 3 were related to portable ultrasound
imaging [6]. European Commission Telematics Technologies Programme had
conducted “EU-TeleIn Vivo 3D ultrasound telemedical Workstation Project (Project
code HC4021)” to develop portable 3D ultrasound imaging device which enables
long distance telecommunication in dangerous, isolated areas or countryside [7]. 6
European countries, 13 research institutes had participated in this project, and the
project initiated continuing development of portable ultrasound imaging device for
telemedicine. Ultrasound probe, as the key technology of ultrasound imaging
diagnosis device, is composed of wire and connector arranging a great number of
ultrasound elements in a form of array and connecting such to the main body of
the ultrasound imaging device. Ultrasound smart probe locates ultrasound Rx/Tx
circuit, which is normally planted in the main body of the existing devices, inside
the probe so that it prevents possible signal losses caused by long wire. It is also
considered as a material technology for performance improvement and
commercialization of the portable ultrasound imaging device because smart probe
could lighten the main body of such device. As smart probe has not been
introduced to the market globally yet, it is essential in developing portable
ultrasound imaging device.
Bio-signal measurement module is the most basic device in monitoring patient's
status which is indispensable to portable diagnosis system. Technology for
continuous measurement of bio-signal, such as smart product, miniaturizing
technology for portability and convenience of user's, ECG(Electrocardiogram),
NIBP(Non-invasive Blood Pressure), SpO2(Saturation of Peripheral Oxygen) and
respiration has been developed with application of established bio-signal
measurement technology and bio-signal processing technology. However,
- 3 -
development of miniaturization and wireless-type power saving bio-signal
measurement module is still in low level.
Thus, new concept of portable diagnosis system which consolidates ultrasound
imaging device whose need and importance is growing under the various medical
environments such as emergency care, etc. and wireless bio-signal measurement
module that monitors patient's conditions should be developed. Also, it should
provide functions which would allow patient's information including ultrasound
images and bio-signals measured through portable diagnosis system at other sites
to be delivered to the hospital at a remote place, and provide tele-communication
(audio or video) between patients or medical staff at the site and doctors at the
hospital. In addition, the basic requirement of portable diagnosis system is to have
a rechargeable battery in order to not be functionally limited by places. It is
necessary to miniaturize portable ultrasound system while maintaining ultrasound
image quality, since more number of channels of Rx/Tx makes better image but
it would make the device bigger [8, 9].
In this study, we have developed portable diagnosis system built on ultrasound
imaging basis combined with bio-signal measurement module without wire and
patient management system based on the key technologies as follows:
We developed ultrasound smart probe which plants signal processing circuit
such as ultrasound (Rx/Tx) and beam forming inside of the probe, and
implemented wireless interface using bluetooth between small and power saved
ultrasound imaging devices and measurement module for bio-signals such as ECG,
SpO2, NIBP and temperature. By using wireless communication technology, we
minimized the size of the portable ultrasound imaging device and procure
scalability to measure various bio-signals. To minimize the size of the portable
ultrasound imaging device, the number of the channels of the Rx/Tx was
minimized, and it applied algorithm which can maintain high quality image similar
- 4 -
to that of the commercialized ultrasound imaging system. Portable ultrasound
imaging device developed in this study supplies B-mode and color-flow doppler
mode and sends ultrasound images to the hospital using wired/wireless LAN.
Bio-signal measurement module is able to measure ECG/respiration, SpO2, NIBP,
temperature and send bio-signal data to portable ultrasound imaging device (main
body). Ultrasound images and bio-signals acquired by portable diagnosis system
are sent to the hospital at real time with patient's basic information. User can
select the menu to display ultrasound images and bio-signals respectively or at
the same time according to graphic user interface (GUI). Chapter 2 explains
portable ultrasound imaging device including ultrasound smart probe and chapter 3
accounts for bio-signal measurement module and wireless interface describing
wireless bio-signal measurement module. In chapter 4, integrated system
combining portable ultrasound imaging device and wireless bio-signal
measurement module is introduced. The result of this study is introduced in
chapter 5 to be followed by chapter 6 which is featuring the conclusion of this
study.
- 5 -
Chapter 2
Portable Ultrasound Imaging Device
2.1 Imaging algorithm for portable ultrasound imaging device
B-mode image as the basic image of the ultrasound image shows clinical
information about cross-section of the body, and its image quality depends on the
capacity of the resolution, Signal-to-Noise Ratio(SNR), contrast, penetration and
frame rate. The capacity relies on the way of Rx/Tx, signal management methods
and characteristic of the circuit[10]. Ultrasound signals are converted to electrical
signals by array transducer, ultrasound imaging device sends these signals to the
display device after signal processing. The number of the element in the array
transducer is called the channel number. The distance between array elements is
decided by Rx/Tx signal's wave length and the number of transmission element
is fixed by the size of the diameter.
The resolution of the ultrasound image means minimum recognition unit that
sets up border line between tissues. The resolution is proportioned by the number
of the Rx/Tx channel. The number of the Rx/Tx channel effects to the device
directly, it needs new algorithm that uses small amount of channels but performs
as similar as the device which has many channel and good image quality[10]. To
overcome technical difficulties getting high quality resolution with less number of
channels, ultrasound imaging technology has been studied[11, 12]. In this study,
while applying limited number of channels to minimize the size of portable
ultrasound imaging device, efficient algorithm such as sparse array and extended
aperture was used for good image quality same as commercialized products. In
other words, the resolution of only 32 channel ultrasound device was similar to
- 6 -
Fig. 1 Example of the sparse and combination array
that of the commercialized 64 channel ultrasound product by applying periodic
sparse array and extended aperture in this study.
2.1.1 Periodic sparse array
While general method of ultrasound imaging using array transducer uses all
array elements within diameter, periodic sparse array uses some of the array
elements distributed sparsely and reduces the number of channel[13]. The less
number of channels makes low resolution as effective aperture get smaller. To
overcome this imperfection, array can be combined as Fig. 1 below or uses
sparsely to make efficient diameter bigger. However, these ways tend to make
grating robe in image so it has been developed efficient way to reduce grating
robe[14-16]. In this study, research on applying periodic sparse array to 32
channels minimizes grating robe for the most and presents the way to get similar
resolution as 64 channels.
Fig. 2 shows the general model of any periodic sparse array. Colored squares
are the elements in use, consecutive L elements are used with P array element
period(1≤L≤P). Any case of the periodic sparse array can be defined with P and
L as (Pt, Lt) and (Pr, Lr) respectively.
Fig. 3 shows the image that Fully Sampled Array(FSA) is 64 on above of the
left and 32 on above of the right. At the bottom of the Fig 3, image is seen as
- 7 -
(Pt, Lt) and (Pr, Lr) are all (2, 1) on the left, (Pt, Lt) is (3, 2) and (Pr, Lr) is (2,
1) on the right. At the right bottom of Fig. 3, it has equivalent resolution and
contrast compared with FAS(64), above of the left of Fig 3.
Fig. 2 General model of the periodic sparse array
Fig. 3 Images using periodic sparse array
- 8 -
2.1.2 Extended aperture
The number of channel in ultrasound system means the number of array
elements once used for Rx/Tx. As splitting the diameter of ultrasound to N small
channel groups, N times stronger effect can be obtained by synthesizing with
small amount of channels[17, 18]. Thus, this Rx/Tx method is called extended
aperture. Diameter increases and resolution get better with increasing N, but frame
rate the images decreases due to N times Rx/Tx for one scanning line. Therefore,
ultrasound images cannot be provided at real time if the number of Rx/Tx group
increases more than they need. Extended aperture is the algorithm that is able to
procure active focused good quality images. This extended aperture is appropriate
to portable ultrasound imaging device requiring power saved on account of getting
good resolution using less number of channels.
Fig 4. shows the example of extended array. Black parts are the channels in
use while white part are not and it performs twice process of Rx/Tx for one
scanning line. At first receive, signals are sent from 32 channels at middle part,
and 32 channels located both ends receive at second time. Total 64 channels gain
signals with 32 channels system. Extended aperture need 64 channel multiplexor
from 64 channel smart probe to switch Rx conversion element combination. In this
study, we implemented Low Voltage Switch(LVSW) and chose 32 channels from
the middle or both sides by extended diameter control signal in LVSW.
General B-mode image is on the left and extended aperture image is one the
right in Fig 5. Fig 4. describes ultrasound images obtained by commercialized
portable diagnostic system to see changes in images during being subjected to
extended aperture. (a) is the case not using extended aperture, (b) is the one
using extended aperture. As known from the Fig 5, images using extended
aperture are increased efficient diameter and followed increased resolution.
- 9 -
Furthermore, extended aperture images are generally good to describe the tissue
borderline of the liver, Splenic Vein(SV) and pancreas as well. Hence, more
clinical valuable information is opt to get from extended aperture.
Fig. 4 Examples of the extended array
(a) (b)
Fig. 5 (a) General image (b) Image using extended
aperture
- 10 -
2.2 System structure of the portable ultrasound imaging device
Due to many required calculation in the signal process of the color-flow system,
color-flow system is only used for big devices with high specification organized
with one ASIC and several FPGA. Portable diagnosis system is a small-sized
ultrasound imaging device, whitch has been developing algorithm to process
color-flow system efficiently. Portable ultrasound imaging device is constituted by
various parts as presented in Fig. 6. To make this system, development of the
key products such as beam former or back-end is necessary. Rx beamformer,
TxPG, Rx/Tx analog real time controller and quadrature demodulation were
gathered in one chip, beamformer FPGA, to be appropriate with portable imaging
device in back-end processor. Echo Processor, digital scan converter and RTC
controller are gathered in one chip, back-end processing FPGA, to be appropriate
with portable imaging device in back-end processor. After back-end processor
performs signal processing for ultrasound image, signals are converted by digital
scan converter to output images on the screen.
- 11 -
Fig. 6 Block diagram of the portable ultrasound imaging device
- 12 -
Fig. 7 shows the functional diagram of the echo processor. Magnitude calculator
detects envelop from inphase and quadrature signals received from digital
receiver(DR). Square root block implements separate IP using CORDIC algorithm
to gain accurate value with small hardware. Log compressor performs nonlinear
conversion of the detected echo envelope using functional formula. Log function
used in log compressor saves log values calculated already and refers to the Look
Up Table(LUT). Edge enhancement filter emphasizes the edge of the images for
ultrasound images to be clear. Persistence block using many frames takes charge
to reduce noise and make images clear.
Fig. 7 Block diagram of the echo processor
Digital scan converter(DSC) performs to change data managed by the unit of
scanning line to the data adapted to display format. Ultrasound imaging device
based on current general PC is fast to PC manages digital scanline converter.
However, portable ultrasound imaging device should use embedded CPU which has
difficult in digital scan converter as software by its characteristic, we implemented
hardware. Fig. 8 shows digital scan converter, and efficiency of the hardware is
considered to design combining with other signal management block to processor
in the back-end board.
- 13 -
FIFO &FIFO Controller &
Data alignEcho data
US 8 bit
US 16 bit
SDRAM(Echo data)
Address & CoefficientGenerator
US 16 bitData align Interpolator
32 bit
SDRAM controller( Echo data )
SDRAM0(Pixel data)
SDRAM1(Pixel data)
SDRAM controller( Pixel data )
CPU interfacecontroller
32 bit
16 bit
16 bit
Dataalign
8 bit
Data align & FIFO
16 bit
32 bit
12 bit
Fig. 8 Block diagram of the digital scan-line converter
In this study, it was designed the logic that calculates coordinate conversion of
the digital scan converter and calculating coefficient, and the logic was put into
the chip to reduce the number of exterior memory. Through time-sharing control
using echo data save memory with one FIFO, the number of exterior memory
saves existing echo data reduces by half. The size the circuit has been decreased
by implementation of the interface circuit to display images without video
management device for adapting to portable diagnosis system based on embedded
CPU. Designed digital scan converter runs with the clock speed of 90MHz for
real-time performance and constitutes 128 scanning line sending ultrasound Rx/Tx
process 128 times according to the characteristic that the system has small display
device. Rx/Tx process performing time per one period is under 266.6us to adjust
30Hz frame rate. And the system is designed to serve 2400 pixels on each
processes, 640*480 image size can be displayed at real-time.
- 14 -
2.3 Power supply for portable ultrasound imaging device
To make portable ultrasound imaging device, it should be developed not only
new image algorithm to get good image quality as many number of channel in
spite of less number of channel but also power saved system regarding as
characteristic of portable device operated by chargeable battery. This study has
developed power supply in considering characteristics of portable system.
Both various voltages and sustained high voltage are required to use several
components for the portable diagnosis system and to obtain good quality images
of the ultrasound respectively. Furthermore, in designing the system, power
consumption should be minimized in considering battery operating. Power
consumption of the every IC elements to contrive power module is expected, and
decided voltage operation as B-mode(about 36W, available to operate 0.5~1 hour),
B-mode+Color-mode(about 72W) for power supply. Table 1 shows the power
management mode of the system. It is distinguished by each image modes and
this system implements to cut off from power supply of components except
essential based on system status. It is confirmed by this management of the
power supply that ultrasound imaging device maintains to run more than 1 hour
consequently. Power of the ultrasound imaging device needs high voltage more
than ±60V so the battery is chargeable. Fig. 9 shows the power circuit of the
portable ultrasound imaging device and lithium polymer battery.
CPU LCD Back-end Beamformer
Ultrasound imaging ON ON ON ON
Standby ON OFF OFF OFF
Power Off OFF OFF OFF OFF
Table 1 Power management mode of developed system
- 15 -
Fig. 9 Power circuit and battery
- 16 -
2.4 Ultrasound smart probe
In considering that portable diagnosis system is used at emergency site, it ought
to be widely used for the organ such as abdomen or heart different from general
ultrasound diagnosis device. Generally, ultrasound device observes by curved linear
array to see abdomen, organic with linear array and for cardiac with phased array.
Phased array has strong points that abdomen and cardiac are able to be diagnosed
by dynamic focusing and beam steering at the same time. Smart array for
ultrasound smart probe has been chosen to use 64 channel phased array for the
upper reason.
Mostly, probe having center frequency from 2MHz to 5MHz are used for
observation of the cardiac and abdominal region. At the point of view the
characteristic that ultrasound penetrates body, too high frequency does not have
good penetration depth, and if frequency is too low image resolution decreases. So
center frequency of the ultrasound smart probe in this study implements to be
3MHz. To make center frequency from 2MHz to 5MHz with actual 3MHz -6dB
fractional bandwidth was settled over than 57%. Factors effected to axial
resolution of the images are center frequency of the probe and length of the
ultrasound pulse in space domain. Length of the ultrasound pulse inside of the
body quantitatively match with pulse duration time in time domain. In this study,
pulse width pointing -20 dB from ultrasound peak of the impulse response defined
to use, and so does the transducer of which characteristic(≦1.2 µsec) is lower
than 1.4 µsec which is categorized as high quality probe. Focal depth is decided to
be 85mm considering widely use of the portable diagnosis system. Loop sensitivity
affects dynamic range of the system and measures to estimate how deep it can
diagnose. Loop sensitivity is more than -50dB to perform as good as
commercialized probe.[19, 20, 21]
- 17 -
Fig. 11 Developed 64 channels smart probe
2.4.1 Wireless smart probe
In this study, the size of the portable ultrasound imaging device has been
reduced by low voltage switch(LVSW) for extended aperture in hardware of the
system and insertion the limiting amplitude circuit which protects high voltage
pulse from the system as Tx processing into ultrasound transducer. Fig. 10 shows
structure of the smart probe suggested in this study. Manufactured 64 channel
smart probe and board are described in Fig. 11, LVSW circuit and limiter circuit
are inserted. Developed smart probe has 64 channel array and 32 channel PCB
(80×26mm), 2 pieces inside in order to limit the size of the portable ultrasound
imaging device, 145×100×20 mm.
Fig. 10 System structure of the smart probe
- 18 -
And wireless communication technology is applied for convenience and
usefulness of the portable ultrasound imaging device. Wireless USB interface
technology is implemented to use between ultrasound imaging device and smart
probe. Still image or moving image activates within near distance as 2~3m and it
is 5 frame/sec in moving image. It is shown that wireless smart probe can be
commercialized. Fig. 12 shows structure of the wireless smart probe. Fig. 13
shows experimental environment of wireless smart probe.
Fig. 12 Block diagram for wireless smart probe
(a) (b)
(a) Experimental environment (b) Image from wireless smart probe
Fig. 13 Wireless smart probe
- 19 -
2.4.2 Design ultrasound smart array and performance evaluation
Fig. 14 shows general structure of the ultrasound array. The structure of the
Fig 14. Basic structure of the ultrasound array
ultrasound array is designed using finite element analysis package, PZflex to
satisfy established purpose. Fig. 15 shows finite element analysis model and field
analysis of the ultrasound. Fig. 16 shows the simulation result of the time and
frequency domain according to pulse-echo response. The simulation result directing
azimuth on radiant pattern for one element describes as well. The number of the
finite element in finite element analysis is 0.5 millions.
- 20 -
Fig. 15 Finite element analysis model and ultrasound field analysis
Fig. 16 Result of the simulation (upper: characteristic of time and
frequency domain, bottom: pattern of ultrasound radiation)
- 21 -
Table 2 shows the result for structure variables of the ultrasound array
according to above. Independent distance, pitch, is settled for FOV(Field of View)
to be 90 degrees not to come out grating lobe as the beam steers toward 45
degree. Elevation length of the elevation direction is decided to satisfy focal depth,
85mm based on the result of sound field analysis described in Fig. 17.
variables of the array unit design value
Element pitch µm 300
Kerf width µm 50
Elevation length mm 14
Thickness of Lens mm 0.96
Table 2 Structural variables of the ultrasound array and result
of the design
(a) (b)
(a) elevation sound field (b) 45b〫eam steering
Fig. 17 Result of ultrasound field analysis
- 22 -
Table 3 indicates the result of the characteristic measurement about 10 yield
array produced in final estimation year and repeatability is very good.
1. number
of
element
2. loop
sensitivity
(3.0MHz)
3. -6dB
center
frequency
4. -6dB
fractional
bandwidth
5.
sensitivity
uniformity
6. -20dB
pulse
width
8. bad
element
Spec.
Proto #
64
channel>-50dB
3.0 +/-
0.15 MHz>57% < 1.8 dB
< 1.2
µsec
# of bad
elements
001 64 -48.2 2.91 70.10% 0.3 0.92 0
002 64 -48.6 2.94 71.43% 0.2 0.91 0
003 64 -47.5 2.96 69.93% 0.3 0.91 0
004 64 -48.6 2.95 70.51% 0.3 0.91 0
005 64 -48.5 2.93 70.99% 0.3 0.91 0
006 64 -47.6 2.96 69.59% 0.3 0.91 0
007 64 -48.7 2.94 69.73% 0.3 0.91 0
008 64 -48.8 2.92 70.89% 0.3 0.92 0
009 64 -48 2.95 70.51% 0.2 0.91 0
010 64 -47.6 2.97 71.04% 0.2 0.91 0
Averaging 64 -48.21 2.943 70.47% 0.27 0.91 0
Table 3 Result of the characteristic measurement about 10 yield array
- 23 -
Pulse-echo test device is used for evaluation of acoustic characteristic on the
ultrasound smart array and the test result is denoted in Fig. 18. As the
characteristic estimation, smart array satisfies with the purpose and proves good
quality compared with conventional probe.
Fig. 18 Result of the manufactured smart array pulse-echo test
- 24 -
Fig. 19 shows the result of the measurement in ultrasound smart array. In the
beam measurement result directing elevation, developed smart array has 81mm
focal depth, and -3dB minimum beamwidth is 2.28mm. Also, -6dB acceptance
angle is 47 degree from the result of the beam field measurement directing
Azimuth.
Fig. 19 Result of the measurement for beam characteristics
in ultrasound smart array
- 25 -
Ultrasound smart probe performs the best when property of electricity between
ultrasound imaging device and smart probe are matched. Thus, property of the
electricity according to the frequency in the manufactured smart array is
measured, and Fig. 20 shows electrical property of the conventional probe being
used to compare with smart probe array. As shown in the result of the impedance
measurement, ultrasound smart array has the characteristic of resonance
absolutely.
(a) (b)
(a) Using probe array (b) Smart probe array
Fig. 20 Result of impedance measurement of the manufactured smart probe
- 26 -
2.4.3. Manufacturing of the ultrasound smart probe
Smart probe for portable ultrasound imaging device consists of the smart array
and smart probe board, low voltage switch(LVSW) and limiter circuit. Fig. 21
describes ultrasound smart probe.
(a)
(b)
(a) Front-end of the ultrasound and block diagram
for smart probe (b) Ultrasound smart probe
Fig. 21 Developed ultrasound smart probe
- 27 -
2.5 Portable ultrasound imaging device based on embedded PC
Portable diagnosis system is designed as Fig. 22 to maintain small size and be
efficient in the resolution of ultrasound image while working system stable.
System improves convenience in manufacturing, reduces the size of the board and
is divided into two boards to protect interference between the signals of the
analog and digital.
Fig. 22 System structure of the portable ultrasound imaging device
Rx/Tx of the ultrasound imaging device and beam former board implement all the analog
components for Rx/Tx and beam former using FPGA described in Fig. 23. Fig. 24 shows
the combination with switching box connecting Rx/Tx, beam former board and smart probe.
- 28 -
Fig. 23 Block diagram of Rx/Tx of the ultrasound and for beamformer circuit
Fig. 24 Connection part of the smart probe(left), Rx/Tx of the ultrasound and
beamformer(right)
- 29 -
Rear part of the ultrasound and embedded system board use S3C6400 of the
Samsung corporation to increase capacity of the system, Fig. 25 shows the circuit.
Fig. 25 Back-end of the ultrasound and embedded system
board
The performance of portable ultrasound imaging device is measured after
integrating the ultrasound smart probe, power module, front-end and back-end
part of the ultrasound board such as Fig. 26. As mentioned above, back-end part
of the board was re-designed to improve the performance of portable ultrasound
imaging device and was integrated as Fig. 27.
- 30 -
Fig. 26 Integrated portable ultrasound imaging device
Fig. 27 Revised portable ultrasound imaging device
- 31 -
CHAPTER 3
Wireless Bio-Signal Measurement Module
It needs to provide not only image information inside the body but also various
bio-signal information including ECG, SpO2, NIPB and temperature when medical
staffs monitor the patient's status in remote site. In this paper, the purpose of the
development of bio-signal measurement module is to measure various bio-signals
mentioned above and make non-invasive/intelligent bio-signal measurement module
providing analysis results. Especially, bio-signal measurement module was
implemented to combine with portable ultrasound imaging device using wireless
communication.
Wireless bio-signal measurement module is able to measure bio-signal parameter
such as ECG, SpO2, NIBP and temperature, these four bio-signal parameters are
collected from patients, and sent to the portable ultrasound imaging device by
bluetooth. Fig. 28 shows formation of the bio-signal measurement module.
Fig. 28 Block diagram for wireless bio-signal measurement module
- 32 -
Main processing part of the bio-signal measurement module applies signal
processing algorithm to original signals from sensor, and gets vital signs of the
bio-signal. In the result, vital signs and waveform data are sent to the portable
ultrasound imaging device by wireless communication, bluetooth.
Main processing part consists with ARM9 processor, CPU(S3C2440A), NAND
Flash memory use for the domain of the program, SDRAM for save data, serial
communications controller receiving original signals, power and timer as Fig 29
shows.
Fig. 29 Main processing diagram of the system
- 33 -
Main software of the bio-signal measurement module can be divided into boot
loader part and application software part. Boot loader performs hardware driving
or initial setup and includes function to upgrade software, application software has
algorithm to calculate main parameter value from bio-signals and includes serial
communication controlling function to send data and driver to manage peripheral
functions of the hardware. Fig. 30 shows the block diagram which describes whole
main software.
Fig. 30 Overall structure of the main software
- 34 -
3.1. ECG design
ECG is constituted 1 channel system measured from RA, LA, LL using 3-wire
cable. It is to select one of the lead I, II, III[22]. The characteristic of the signal
frequency is 0.2∼30Hz, input range is ±7㎷, amplitude range of the input signal is
±400㎷. Pacer pulse signal is not confused with QRS due to Pacer pulse detection
function. According to safety standard, ECG measurement circuit is designed to be
sustained 4000V withstand voltage, leakage current for patients to be CF grade.
ECG measurement circuit is designed to be protected from cardiac defibrillator.
Sampling of ECG signal is 1,000samples/sec, resolution of the AD converter uses
12bit.
3.1.1. Design for hardware and software
Hardware of the ECG consists as describing in Fig. 31, (a) is the hardware
diagram with analog circuit used generally, (b) is the hardware diagram with full
digital circuit developed in this study and the size of hardware is reduced to 40%
compared with existing. Table 4 presents the performance of the hardware system
with analog circuit and hardware with digital circuit developed in this study. The
baseline drift of ECG signal is caused by electrode's attachment and motion
artifact. In this study, the baseline drift rejection time was improved under 0.1sec
and power consumption was minimized to 1.82W considering property of the
portable diagnostic system.
Fig 32 is the ECG circuit of the wireless bio-signal measurement module and
final implemented board. And Fig. 33 shows the flow of the software in ECG.
- 35 -
Item Analog system Digital system
ECG stabilizing time 4sec 0.1sec
Power consumption 5W 1.82W
Table 4. Performance improvement of the developed hardware system
(a)
(b)
(a) Block diagram of ECG hardware with analog circuit
(b) Block diagram of developed ECG hardware with full digital circuit
Fig. 31 Block diagram of ECG hardware
- 36 -
Fig. 32 Developed ECG board
- 37 -
Fig. 33 Softwate flow of the ECG
- 38 -
3.1.2. QRS complex detecting algorithm
At emergency site, QRS complex of ECG in the bio-signal measurement module
should be detected at real-time. In this study, to minimize delay time of the QRS
complex detection, variable threshold method was used after signal processing[23].
As detecting QRS complex at real-time, band-pass filter was used to minimize
delay time in signal processing and variable threshold value was applied to detect
QRS complex. Fig. 34 shows the flow of the QRS complex detecting algorithm.
QRS complex detection algorithm includes signal processing interval, absolute
refractory period, T wave expectation interval, expected QRS complex interval and
comparing with threshold value.
- 39 -
Fig. 34 The flow of QRS complex detection algorithm
- 40 -
Basically, QRS complex detection algorithm uses the method comparing with
signal power, after signals constituted QRS complex and high frequency signal
with highest signal-to-noise ratio(SNR) is filtered by band-pass filter. To detect
arrhythmia at real-time, ECG signal is filtered in the frequency range, 10~15Hz,
using 2nd-order Butter-worth filter. Variable threshold value is adjusted using the
latest eight QRS complex detected. The threshold value is set by 65% of the
average value of latest eight QRS complex's peak values. Each peak of the QRS
complex is searched in absolute refractory period after QRS complex is detected.
In case of tall T wave, the problem which can occur in changing frequency band
of the band-pass filter in signal processing is to recognize the T-wave as QRS
complex. To reduce this QRS complex detection error, the higher threshold value
is applied in the range where T wave exists. In this range, threshold value is
used 80% of the maximum value of latest eight QRS complex's peak values. QT
interval is adjusted in considering ventricular rate and formula for QTc is used
[24]. Formula follows
.
QT interval of normal ECG is 0.41sec, range of the T wave can be assumed
using QTc in considering ventricular rate. To detect QRS complex at real time, it
is good to detect in low energy state and low threshold value is used in expected
the range of the QRS complex. The range of QRS complex detection is set by
calculating R-R interval using ventricular rate, and considering arrhythmia of
which R-R interval varies gradually QRS complex is assumed to be occurred from
80% of the R-R interval. In this case, used threshold value is the 50% of the
average value of latest eight QRS complex's peak values. The threshold value is
getting lower while ECG signal has noise, noise of ECG signal can be detected as
- 41 -
QRS complex. The threshold value is changed judging noise existence before
expected range of QRS complex. If magnitude of the signal exceeds threshold
value applied by QRS complex ranges, regards as QRS complex and calculates
heart rate(HR). And, calculated expected interval of the T wave and expected next
QRS complex range.
- 42 -
3.1.3 Evaluation of QRS complex detection algorithm
(1) QRS complex Detection Performance
This experiment is subjected to QRS complex that has various sizes and widths
to evaluate the detection performance under “4.2.6.1 Range of QRS wave amplitude
and duration” of EC13. The result of experiment is the same as table 5, and the
result was satisfied with all the items of detection.
QRS SignalBPM Acceptance
Criteria Result
30 80 120 200 250 300
0.15mV 100ms 29 79 119 199 249 299
Within
±3BPM
Pass
0.15mV 40ms 29 79 119 199 249 299 Pass
0.15mV 70ms 29 79 119 199 249 299 Pass
0.15mV 80ms 29 79 119 199 249 299 Pass
0.15mV 120ms 29 79 119 199 249 299 Pass
0.5mV 100ms 29 79 119 199 249 299 Pass
0.5mV 40ms 29 79 119 199 249 299 Pass
0.5mV 70ms 29 79 119 199 249 299 Pass
0.5mV 80ms 29 79 119 199 249 299 Pass
0.5mV 120ms 29 79 119 199 249 299 Pass
1mV 100ms 29 79 119 199 249 299 Pass
1mV 40ms 29 79 119 199 249 299 Pass
1mV 70ms 29 79 119 199 249 299 Pass
1mV 80ms 29 79 119 199 249 299 Pass
1mV 120ms 29 79 119 199 249 299 Pass
5mV 100ms 29 79 119 199 249 299 Pass
5mV 40ms 29 79 119 199 249 299 Pass
5mV 70ms 29 79 119 199 249 299 Pass
5mV 80ms 29 79 119 199 249 299 Pass
5mV 120ms 29 79 119 199 249 299 Pass
Table 5 The result of detection performance according to size and width of QRS complex
- 43 -
Only input QRS BPM
(0.5mV 100ms 80bpm)
Input Chopping wave BPM
(0.1Hz 4mV)
Acceptance Criteria
79 79 Don’t change over ±8BPM
Table 6 The result of QRS complex detection according to baseline change
If there is a baseline wandering, the experiment is conducted under “4.2.6.3” of
EC13 and measured by triangle wave input of 0.1Hz from 4mV as an input signal
and baseline wandering signal. Table 6 is satisfied with the standard of EC13.
(2) QRS Detection Performance of ECG Signal Where Arrhythmia Exists
It is to test the “4.1.2.1 Disclosure of performance specifications, e) Heart rate
meter accuracy and response to irregular rhythm” of EC13. This experiment is to
evaluate the QRS complex detection performance in the condition of arrhythmia of
which shape and size of QRS complex change. The waves are standardized with
respect to four types of arrhythmia waves shown to Fig. 35. The figure includes
most of the cases enough to evaluate the QRS detection. The result passed the
standard without any QRS complex detection errors of arrhythmia as being shown
in the Table 7.
- 44 -
(a)
(b)
(c)
(d)
(a) Ventricular bigeminal experiment
(b) Slow alternating ventricular bigeminal experiment
(c) Rapid alternating ventricular bigeminal" experiment
(d) Bidirectional systoles experiment
Fig. 35 QRS Detection of Arrhythmia
- 45 -
irregular rhythm HR(bpm)Acceptance
Criteria Result
3a Ventricular bigeminal 77∼82 80±8Bpm Pass
3b Slow alternating ventricular
bigeminal63∼68 60±6Bpm Pass
3c Rapid alternating
ventricular bigeminal118∼120 120±12Bpm Pass
3d Bidirectional systoles 82∼94 90±9Bpm Pass
Table 7 Results of QRS complex detection performance of the arrhythmia
(3) Removal Performance of Pacer Pulse
It is to carry experiment under “4.1.4.1 Pacemaker pulse rejection without
overshoot” of EC13. The experiment evaluates QRS complex performance either
when the function of pacer pulse detection is used or when the function is not
used. The pacer pulse should not be detected as QRS complex when pacer pulse
has been used. The wave shape of pacer pulse is very big and unique like QRS
complex, so it is not easy to distinguish from QRS complex. This is evaluated
under two conditions: One is under a normal operation that QRS complex is
synchronized by pacer pulse, and the other is under an abnormal operation that
only pacer pulse occurs but not QRS complex. In Fig. 36, the pacer pulse and
QRS complex exists at the same time, but the detection of pacer pulse is not
applied. The result is that pacer pulse is detected as QRS complex. In Fig. 37, the
detection of pacer pulse is used, but QRS complex is detected correctly. Table 8
shows the evaluation result, and it is satisfied with the standard EC13.
- 46 -
Fig. 36 QRS detection in case of not using the pacer pulse detection
at pacer pulse and QRS complex
Fig. 37 QRS detection in case of using the pacer pulse detection
at pacer pulse and QRS complex
- 47 -
Pacer Pulse Pacer Detect Result
Interval Duration Amplitude OFF ON
40ms
0.1ms
+/-2 mV Pacer QRS Pass
+/-10 mV Pacer QRS Pass
+/-100 mV Pacer QRS Pass
+/-200 mV Pacer QRS Pass
2ms
+/-2 mV Pacer QRS Pass
+/-10 mV Pacer QRS Pass
+/-100 mV Pacer QRS Pass
+/-200 mV Pacer QRS Pass
150ms
0.1ms
+/-2 mV Pacer QRS Pass
+/-10 mV Pacer QRS Pass
+/-100 mV Pacer QRS Pass
+/-200 mV Pacer QRS Pass
2ms
+/-2 mV Pacer QRS Pass
+/-10 mV Pacer QRS Pass
+/-100 mV Pacer QRS Pass
+/-200 mV Pacer QRS Pass
250ms
0.1ms
+/-2 mV Pacer QRS Pass
+/-10 mV Pacer QRS Pass
+/-100 mV Pacer QRS Pass
+/-200 mV Pacer QRS Pass
2ms
+/-2 mV Pacer QRS Pass
+/-10 mV Pacer QRS Pass
+/-100 mV Pacer QRS Pass
+/-200 mV Pacer QRS Pass
Table 8 The result of pacer pulse detection performance at pacer pulse
and QRS complex
- 48 -
3.2 SpO2 Design
SpO2 is a non-invasive device that monitors the amount of oxygen in the total
Hemoglobin(Hb). The pulse rate is depended on variation of the amount of
absorbed light wavelength. The red or infrared rays laminated from probe pass
the capillary vessels of the finger tips and are changed to electrical signals by a
light detector in the probe. The received electrical signals indicate the number of
pulse and display the quantity of oxygen saturation to the screen.
3.2.1 Design of Hardware and Software
The system configuration of SpO2 is shown in Fig. 38, and the function of each
block is as follows:
l RED Driver: RED LED Drive Signal
l IR Driver: IR LED Drive Signal
l Timing Circuits: Selectively controls the signals of RED and IRed
l ADC PART: Digitalize the analog signal from previous column. This data is
connected to IO PROCESSOR through SPI(Synchronous Peripheral Interface)
method. The essential input/output signal is a line number 4, and the basic
lines are SCLK, SDOUT and SDI to select AD and to deliver CS and SPI
communication. Fig. 39 is the hardware circuit of oxygen saturation. And
Fig. 40 is its software circuit.
- 49 -
Fig. 38 System diagram of SpO2
- 50 -
(a)
(b)
Fig. 39 (a) Circuit of SpO2 (b) Board of SpO2
- 51 -
Fig. 40 Software flow of SpO2
- 52 -
3.3 NIBP(Non-invasive Blood Pressure) Design
It uses an oscillometric method that measures the maximum, minimum and
mean blood pressure.
3.3.1 Hardware Design
The design of NIBP is shown to Fig. 41, and each functions are as follows:
l PRESSURE SENSOR: A sensor that detects the pressure inside the blood
pressure cuff and changes it to the electrical signals
l Solenoid Valve: Consists of two valves -- one is a valve for continuously reducing
the pressure of cuff and the other is a valve for reducing the pressure at once
l PUMP: An air pump for giving air pressure to cuff
l ARM PROCESSOR: A CPU that operates blood pressure measuring algorithm
l Safety PROCESSOR: Ensures a patient's safety if any fault occurs by
cutting the power to make motor and valve stop
Fig. 41 Block diagram of the non-invasive blood pressure
- 53 -
Fig. 42 presents hardware circuit of the non-invasive blood pressure.
(a)
(b)
Fig. 42 (a) Circuit of the NIBP (b) Board of NIBP
- 54 -
Fig. 43 shows non-invasive blood pressure software flow.
Fig. 43 Software flow of the non-invasive blood pressure
- 55 -
3.4 Temperature Design
The temperature converts the values of resistance to the electrical signals as
the temperature changes, and it also expresses the values into quantities using the
signal processing algorithm.
3.4.1 Hardware Design
The design of temperature is shown in Fig. 44, and the function of each column
is as follows:
l R-V Converter: Converts the value of resistance measured by the
temperature sensor to electrical signal
l 16 SAR ADC: A converter that changes the analog electrical signal in regard
of temperature to the digital signal
l MCU: Conducts the control to measure a temperature
Fig. 44 System diagram of the temperature
- 56 -
Fig. 45 is the hardware circuit and the board of temperature. And Fig. 46 is
the software flow chart of thermometer.
(a)
(b)
Fig. 45 (a) Circuit of temperature (b) Board of temperature
- 57 -
Fig. 46 Software flow of the temperature
- 58 -
3.5 Wireless interface of bio-signal measurement module
Near field wireless communication using bluetooth technology, was developed to
send the measured bio-signal data to the portable ultrasound imaging device.
Bluetooth has advantages on two counts. One is the low price with low power
(100mW) and the other is the safety in security because it separates the
frequency band to send the data with those frequencies. Also, bluetooth can send
the signal through the obstacles such as walls or bags, so the electrical wire or
connection is not necessary to be inspected physically because it can send/receive
the signals through any obstacle. And the frequency is omni-directional so it is
easy to use because of no limited angle to connect each device. And it is a
utilized bluetooth technology in the worldwide as most of countries use the
standard of bluetooth. So, bio-signal measurement module using the bluetooth can
freely exchange data with the portable diagnosis system whenever and wherever
it is.
The wireless bluetooth circuit is designed to communicate with a portable
diagnosis system in near field as using a bluetooth class 1 module, BM-310 chip,
commercialized by Insung Electrical Machinery Co., Ltd. Fig. 47 is the picture of
BM-310, and the standard of telecommunication is as below:
Fig. 47 BM-310 bluetooth chip
- 59 -
l The Telecommunication Standard of Bluetooth 1.2
l Faster data transfer rate than UART or USB
l Four power saved mode: Park, Sniff, Hold and Deep Sleep Modes
l EDR(Enhanced Data Rate) Standard (satisfied 0.9 version with the
modulation modes of 2Mbps and 3Mbps)
Fig. 48 shows the block diagram of inside the BM-310 module chip. BM-310
module chip supporting UART interface is a simple mechanism to communicate
with other serial communication devices. Fig. 49 is the block diagram between
BM-310 module chip and MCU, namely for the UART interface between ARM9
CPUs. All the connections of UART is based on the CMOS technique, and the
signal level is from 0 to VDD.
- 60 -
Fig. 49 Block diagram of UART interface between
BM-310 module and MCU
Fig. 48 Block diagram for BM-310 module chip
- 61 -
Fig. 50 and 51 show that the developed hardware of wireless bluetooth
communication module which can send the bio-signal data obtained by the
bio-signal measuring module to portable ultrasound imaging device.
Fig. 50 Wireless bluetooth communication circuit
Fig. 51 Wireless bluetooth communication board
- 62 -
3.6 Integrated wireless bio-signal measurement module
Each function of bio-signal measurement modules including ECG, SpO2, BP,
and temperature are integrated to one module in this study. Fig. 52 is the finally
developed wireless bio-signal measurement module.
Fig. 52 Integrated wireless bio-signal measurement module
- 63 -
CHAPTER 4
System Integration
A portable diagnosis system consists of portable ultrasound imaging device that
provide the ultrasound image shown in Fig. 53, the wireless bio-signal
measurement module that obtains the signal to send it to portable ultrasound
imaging device using wireless bluetooth communication, and the hospital's
server/client system that saves, analyzes, and re-sends those data to.
Fig. 53 Basic concept of integrated portable diagnosis system
- 64 -
4.1 GUI (Graphic User Interface)
It reduces the kernel booting time to 1.5 seconds and application operating time
within 1 second by tracing the booting sequence of Linux Kernel and modulating
the part where it is useless so that can be improved. Ultimately, the real system
booting time that extracts the time for loading Kernel as well as RootFilesystem
in the boot loader and for downloading FPGA image is within 4 seconds.
The GUI was focused on the precise image discrimination and rapid diagnosis.
The basic design of screen is shown in Fig. 54. For the better image
discrimination, image area was occupied as much as possible. For the convenience
and accessibility, the most frequently used menu-buttons are located from left-top
of the screen. For the quick control, simplicity and familiarity of menu icons, the
depth of the menu has been limited no more than two levels.
Fig. 54 Basic design of display
- 65 -
l Image and Information Area: 640 x 480
l Maximum 2 x 6 Menu Buttons and One Module Transfer Button
l Information of Patients and System
l Action Module Information
The information of system and module is displayed on the top or bottom of the
screen, and the display can be on/off according to the user menu set. The
information of system is shown on the screen as it is iconize depicted in Fig. 55,
and the status of the system is displayed in real time.
Fig. 55 Dispaly of the menu
- 66 -
The menu consists of two parts: Common part and module part of the system.
When the system starts, basically the bio-signal measurement module is activated,
so the initial priority of selecting menu is the bio-signal measurement module.
(The initial priority of menu selection, if bio-signal measurement module or
ultrasound imaging device, can be changeable by the user's choice.) Afterwards,
the users can freely choose the menus on the bio-signals or the ultrasound
imaging device module if it is needed. The most menus are limited under 2 depth
in consideration of the user's convenience and its speed.
Common
Module
System On
VitalSignal UltraSound
Setup Patient
- 67 -
Fig. 56 shows the display part of bio-signal screen which consists of the
common menus of bio-signals on the left and the other menus of each parameter
on the right side. The display and alarm can be set by each parameter.
Fig. 56 Display part of bio-signal
Fig. 57 is the display part of ultrasound image which consists of the dependent
menu in accordance with the scan status and the common menu parts. After
selecting Scan mode and optimizing an image to get a desiring image, send it out
using the save and transfer menu button.
When the menu, “Show VitalSignal”, is chosen the screen is converted to
overlap the display of ultrasound image and display of bio-signal shown in Fig.
58. In that event, the user can watch the two contents together at the same time.
Also, on the overlay display, the parameter menu for bio-signal can be selected.
- 68 -
Fig. 57 Display part of ultrasound image
Fig. 58 Display overlapped ultrasound image
and bio-signal
- 69 -
(1) Patient Menu
It is about the information of patients. Registering a new patient and
researching, modifying or deleting the information of patients is possible.
(2) Setup
It consists menus for system and user settings. The design of menus and the
displays are convenient for the users.
- 70 -
Fig. 59 Portable ultrasound imaging device combined with wireless
bio-signal measurement module
4.2 Integrated portable diagnosis system
The integrating procedure for the portable diagnosis system is to confirm the
wireless interface between portable ultrasound imaging device and bio-signal
measurement module and to integrate the menus between ultrasound image and
bio-signal. Fig. 59 shows the integrated portable diagnosis system.
- 71 -
CHAPTER 5
Result
Considering the purpose of this study, to maximize usefulness in emergency, the
device is made no more than 1kg with the small size as 18.5cm(width)x12cm
(length)x2.2cm(height). The resolution for 640x480 is 30 frames/sec with a built-in
battery that can operate a device more than 4 hours, and the system booting time
is a lot reduced to less than 4 seconds. It has a bluetooth chip for wireless
communication between portable ultrasound imaging device and bio-signal
measuring module. The USB helps the device not only to support basic external
memory but also to communicate with a hospital through wired/wireless LAN.
The chapter 2 above introduces the ultrasound image processing methods that
achieves high quality resolution with 32-channel Rx/Tx. The resolution of
32-channel one was close to the 64-channel Rx/Tx. (a) of Fig. 60 is a image
obtained by a simulated experiment; (b) is a image taken by a developed
32-channel portable ultrasound imaging device; and (c) is a image by a
commercialized 64-channel ultrasound imaging device.
- 72 -
(a) (b)
(c)
a) Image by computer simulated experiment, b) Image by developed
32-channel ultrasound imaging device, c) Image by commercialized
64-channel ultrasound imaging device
Fig. 60. Comparison of image of developed 32-channel system
and commercialized 64-channel system
- 73 -
This study performed a comparative evaluation of the image quality from
developed portable ultrasound imaging device and the image quality from
commercialized 64-channel ultrasound device according to the guideline of AIUM
(American Institute of Ultrasound in Medicine). The basic factors for the
comparative evaluation are resolution, penetration, SNR and contrast, but this
study was more focused on the resolution and the penetration. To evaluate
auto-correlation between two saved images, the penetration evaluation was
conducted by fixing a probe to phantom saving the images twice in the same
environment. Fig. 61 shows the results of the auto-correlation while it gets to the
0.5 point. The penetration evaluation is not to observe the correlation of target but
to evaluate the correlation of speckle where irregular reflection occurs for the
precise result, so this study decides to evaluate the part where there are many
speckles rather than where the target exists. While the penetration rate of the
commercialized 64-channel ultrasound device that uses the probe with the same
frequency band is 26.23cm, the developed portable ultrasound imaging device is
30cm enough to support FOV (Field of View). Also, the penetration rate measured
by the auto-correlation method has the auto-correlation upto 28.14cm.
Fig. 62 shows the result of resolution evaluation of the image from developed
portable ultrasound imaging device and the image from commercialized 64-channel
ultrasound device. The criteria required by general ultrasound device in
Axial/lateral is <= 2mm / <= 3mm. However, according to the evaluation result of
the both resolutions of the 64-channel one and the developed device at the
focusing point, the resolutions are 0.86mm / 1.68mm and 0.78mm / 1.62mm
respectively. Hence, the both resolutions of Axial and Lateral are improved by
9.3% / 3.6%. Table 9 is the result of image performance between the developed
32-channel portable ultrasound imaging device and the commercialized 64-channel
ultrasound imaging device.
- 74 -
(a) (b)
a) Penetration of commercialized 64-channel ultrasound imaging device
b) Penetration of developed 32-channel portable ultrasound imaging device
Fig. 61 Image comparative evaluation of the commercialized 64-channel system
and the developed system
(a) (b)
a) Resolution of of commercialized 64-channel ultrasound imaging device
b) Resolution of the developed 32-channel portable ultrasound imaging device
Fig. 62 Image comparative evaluation of the commercialized 64-channel system
and the developed system
- 75 -
Commercialized 64-channel
System
Developed 32-channel
System
Penetration 26.23cm 28.14cm
Resolution
(Axial/Lateral)0.86mm / 1.68mm 0.78mm / 1.62mm
Table 9. Comparison image quality between developed 32-channel system and
commercialized 64 channel system
The color flow motion of the developed portable ultrasound imaging device is
shown in the fig. 63. The very left image is the measuring result, by using a
string phantom, which displays both signals of forward and backward direction. It
is also vertical with probe, so the middle part without Doppler has been observed
a strong reflective signal as usual. Fig. 64 shows the liquid flow in the narrow
pipe using flow phantom in the both forward and backward direction. The
developed field system can control whether or not to use the extended aperture.
Fig. 63 Color flow image from the developed system
- 76 -
Throughout this study, the low power consumpted wireless bio-signal
measurement module was developed to interface with the portable ultrasound
imaging device. Because the developed wireless bio-signal measurement module is
communicated with the portable ultrasound imaging device in the close distance
whenever and wherever it is. Also, since the data communication protocol between
the wireless bio-signal measurement module and the portable ultrasound imaging
device is self-developed, the internationally standardized protocol of the portable
diagnosis system is expected. The effective communication distance between the
wireless bio-signal measurement module and the portable ultrasound imaging
device is 15m, and the wireless communication sensor output is below than 50mW.
In addition, the performance of ECG, SpO2, BP and temperature that is measurable
by the bio-signal measurement module is much more improved.
The portable ultrasound imaging device has a platform using Qtopia that lays a
foundation on the embedded Linux. A device driver related to the developed
hardware, a program for the portable ultrasound imaging device and a data
program was developed. The database program delivers wired/wireless
communication to the server in the hospital to read the information of patients or
make records for them, and even the saved ultrasound image can be sent to the
hospital. Moreover, in the remote site, the software that can watch the ultrasound
images acquired from the emergent site makes people share the status of patient
at the same time. Like Fig. 64, the fact that obtained ultrasound image and the
bio-signal data is sent to the server in the hospital via the portable diagnosis
system was confirmed by a viewer.
- 77 -
Fig. 64 Data viewer of the server in the hospital
- 78 -
CHAPTER 6
Conclusion
The healthcare service has been changed from the existing hospital-oriented to
patient-oriented. And the healthcare service was developed to remote or
home-based system so that people can have the professional healthcare service at
home, office, emergency site, rural area or in the field. The development of the
portable in-vitro diagnostic system using blood as well as the portable diagnosis
system using the bio-signals such as ECG and SpO2 is actively in progress. Also,
one of the image diagnostic systems, ultrasound imaging device, was developed to
portable one by the several global corporations abroad. However, the portable
system with single function has a limit to give patients the better healthcare
service on their way to go to hospital. Thus, this study's aim is to develop a
multi-function portable diagnosis system that the portable ultrasound imaging
device is combined with wireless bio-signal measurement module. So, portable
diagnosis system developed in this study consists of a portable ultrasound imaging
device that supplies ultrasound images, a wireless bio-signal measuring module
that obtains various bio-signals and wirelessly sends the signals to the portable
ultrasound imaging device which is the main body of the system, and a
server/client system of hospital that saves, analyzes and re-sends the ultrasound
image data and bio-signal data obtained by this system.
The most important points to implement the proposed system are to miniaturize
the ultrasound imaging device and keep the quality of image. To make these
possible, this study suggests few channels/high resolution imaging techniques and
implements portable ultrasound imaging device appropriate to the portable
diagnosis system. In this study, for miniaturization, the ultrasound imaging device
- 79 -
has limited channels and creates the similar image quality as commercialized
products using effective algorithms such as periodic sparse arrays and extended
aperture. Applied those algorithms, periodic sparse arrays and extended aperture,
the device can obtain the similar resolution of 64 channels with the 32 channels.
Also, the study minimized the size of system by designing a beam former
integrated all the functions of receiving beam former, TxPG, real time controlling
system of receiving/transmitting parts, and quadrature demodulation function to
one FPGA. Moreover, the design of back-end processor of portable ultrasound
imaging device includes a chip in which has echo processor, digital scan converter
and real time controller appropriate to the portable diagnosis system, so the device
is appropriate to SoC(System on Chip) integrated to embedded system. The
portable diagnosis system, in regard of immediate use in the emergency case,
reduces the booting time within four seconds. The portable ultrasound imaging
device has a chargeable built-in battery with power saved system regarding its
portability. The power is designed after analyzing the characteristics of voltage
operation in the use of B-mode and color flow. When ultrasound imaging device
is operated continually, the voltage operates more than one hour.
This study develops the 64 channel phased array applied a wide band from 2MHz
to 5MHz with a main 3MHz frequency, so the ultrasound imaging device can be
practically useful for the people's organs such as a cardiac or others in the stomach
when an emergency situation occurs. To make the size of portable ultrasound
imaging device minimize, the study developed a smart probe built in LVSW (Low
Voltage Switch) to the probe for the application of extended aperture.
It was developed not only ultrasound imaging device but also bio-signal
measurement module including ECG, SpO2, NIBP and temperature. The developed
bio-signal measurement module was combined with the portable ultrasound
imaging device using wireless bluetooth. The ECG signal is a important parameter
- 80 -
of various bio-signals that monitors status of a patient. Thus, the QRS detection
algorithm developed by this study is satisfied with the EC-13 international
standard of the detection performance such as the performance in accordance with
the size or width of QRS complex, the removing performance of Tall T-wave, the
detecting performance of QRS complex where arrhythmia is located, and the
detection performance of pacer pulse.
To send the each measured bio-signal data to the portable ultrasound imaging
device, it has a wireless bluetooth communication circuits that sends data with a
wireless system. It can be used anywhere in the world because lots of countries
use the bluetooth standardization. Hence, the bio-signal measurement module is
expected to freely exchange data with the portable diagnosis system wherever or
whenever it is. The bio-signal data and ultrasound image obtained from the main
body of system is sent to a hospital in real time so that medical staff in the
hospital can care patients from remote area, so called telemedicine service.
This study brought meaningful results. One is making a portable ultrasound
imaging device of which the longest width is not longer than 15cm, and the other
is achieving the similar image quality of 32-channels with 64-channel devices.
The bluetooth makes wireless communication possible between bio-signal
measurement module and portable ultrasound module and enables to send
bio-signal data and ultrasound image data from main body to a remote hospital.
To maximize the practicality of the system, the further study of the much smaller
device with high function/high quality image and the ultrasound smart probe with
various functions shall be proceed. For the much smaller device with high
function/high quality image, the further study shall be focused on how to deal
with the back-end part using DSP(Digital Signal Processor). For the wireless
ultrasound smart probe that has a menu selecting function itself considering the
user’s convenience in emergency, the further study shall be proceed on that probe.
- 81 -
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국 문 요 약
무선환자감시장치와 결합된 이동형 초음파진단시스템 개발
연세대학교 대학원
생체공학협동과정
장 원 석
최근에 생활수준의 향상 및 의학과 과학기술의 발전에 따른 병원 중심의 의료에서
벗어나 자택, 직장, 응급 현장 등 원격에서 전문적인 의료진단을 받을 수 있는 이동형
진단시스템에 대한 기술개발 및 제품화가 활발하다. 본 연구에서 개발한 이동형 진단
시스템은 병원과 떨어진 다양한 환경에서 환자의 생체신호 및 초음파 영상을 획득하
고 이를 이용하여 고품질 의료 서비스를 제공할 수 있다. 본 연구에서는 응급의료현
장을 비롯한 다양한 환경에서 사용할 수 있는 생체신호와 무선으로 결합된 초음파 영
상기반의 초소형 이동형 진단시스템을 개발하였다. 이를 위해 초소형 초음파 영상장
치, 스마트 프로브 및 무선생체신호측정모듈을 개발하고 통합하였다. 초소형 초음파
영상장치를 만들기 위하여 희박 및 결합 어레이 영상기법과 확장 구경 기법 등의 소
채널/고해상도 초음파 영상 알고리즘을 구현하였다. 또한 빔포머는 프로세서 및 초음
파 후단부 프로세서를 각각 하나의 FPGA로 구현하여 초음파 영상장치의 크기를 줄
일 수 있었다. 특히 개발된 빔포머는 하나의 칩으로 32채널을 처리할 뿐만 아니라 수
신 집속 기능 외에 송신집속 및 쿼드러쳐 디모듈레이션 기능을 포함하며, 확장 구경
기법을 구현한 하드웨어를 스마트 프로브에 내장하여 초음파 영상장치를 소형화 할
수 있게 하였다. 또한 이동형 진단시스템은 휴대가 가능해야 하는 특성을 고려하여
충전이 가능한 전원 공급 장치 개발하였다.
심전도, 산소포화도, 혈압 및 체온을 측정하고 이를 무선으로 초음파 영상장치에
전송할 수 있는 생체신호측정모듈을 개발하였으며, 초음파 영상장치로부터 데이터를
- 86 -
전송받아 저장하거나 재전송할 수 있는 병원의 서버/클라이언트 시스템을 구현하였
다. 사용자의 휴대성 및 편의성을 고려한 초소형 초음파 영상장치의 외장을 디자인
하였고, 이러한 개발 내용을 통합하여 실제 이동형 진단시스템을 개발하였다. 개발된
이동형 진단시스템은 환자중심의 의료진단을 위한 생체신호 및 초음파 영상진단 기술
을 향상시킬 뿐만 아니라 관련 응급의료 분야의 응용 기술 및 초음파 영상장치의 전
반적인 기술력 향상과 국제 산업경쟁력을 획기적으로 개선할 수 있는 계기를 마련할
수 있게 하였다. 본 연구를 통하여 개발된 이동형 진단시스템은 영상장치와 생체신호
장치가 결합된 새로운 개념의 제품으로서 새로운 시장 창출이 가능할 것이며 국가 경
제 발전에 기여할 수 있을 것이다.
핵심되는 말 : 초음파영상장치, 생체신호, 심전도, 스마트 프로브, 이동형진단시스템
