Download a system and a method for extracting human

1
A MEDICAL DATA MONITORING SYSTEM AND A METHOD THEREOF
FIELD OF INVENTION
5
The present invention relates to a medical data monitoring system and a method thereof.
BACKGROUND OF INVENTION
Advancement of medical science contributes towards the human life expectancy. Naturally,
10
proportions of older persons in the society are increasing. Certainly, taking proper care of
these persons is one of the responsibilities of our society. Cardiac rehabilitation is one of the
necessary treatments, because of life long non-stop cardiac activities. Electrocardiograms
(ECG) is the only way to check heart conditions, and if ECG can be done frequently without
leaving home then it is easy to identify the problem by the physician from the ECG history of
15
a person. This has long been requested by physicians.
The known technology vary from a simple ECG recorder that can only monitor the ECG
signal to a sophisticated system with computer analysis and database. Some ECG recorder
has incorporated memory to the device to provide storage for the ECG data and send the
20
digital data to computer for storage later. This type of ECG recorder completes with LCD
display, keypad and mechanism to send the recorded ECG data to the computer to make it
an independent ECG recording device.
Therefore, there is a need for a solution that is able to create health awareness right from
25
home wherein vital medical statistics can be consistently monitored instantaneously.
2
SUMMARY OF INVENTION
Accordingly, there is provided a medical data monitoring system, characterized in that, the
5
system is connectible over a network such that data is accessible via the network, the
system includes a medical data recorder connectible to a computing means by a
microcontroller wherein the medical data recorder further is connectible to a plurality of skin
electrodes, a data converter wherein data from the medical data recorder is convertible into
a transmittable data format in real time, wherein the medical data recorder further includes
10
an amplifier, a filter and an analog to digital converter.
There is further provided a method of monitoring data over a connectible network,
characterized in that, the data is accessible via the network, the method includes the steps
of detecting signals containing medical data, compressing the medical data and sharing the
15
compressed data through the network in real time.
The present invention consists of several novel features and a combination of parts
hereinafter fully described and illustrated in the accompanying description and drawings, it
being understood that various changes in the details may be made without departing from
20
the scope of the invention or sacrificing any of the advantages of the present invention.
3
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention will be fully understood from the detailed description given herein
below and the accompanying drawings which are given by way of illustration only, and thus
5
are not limitative of the present invention, wherein:
Figure 1 shows a block diagram of an ECG recorder in the preferred embodiment of the
invention;
Figure 2 shows a block diagram of communication protocol in the preferred embodiment of
the invention;
10
Figure 3 shows a flow chart showing a method of monitoring data in the preferred
embodiment of the invention;
Figure 4 shows a dimensional view of the plurality of surface electrodes used in the
preferred embodiment of the invention;
Figure 5 show circuit diagrams of amplifiers, filters, analog to digital converters, power
15
supply unit and microcontroller in the preferred embodiment of the invention;
Figure 6 shows a flowchart of the microcontroller firmware in the preferred embodiment of
the invention;
Figure 7 shows a circuit diagram of a RS-232 transceiver in the preferred embodiment of the
invention; and
20
Figure 8 shows a graphical view of actual detection of heartbeat in the preferred
embodiment of the invention.
4
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The present invention relates to a medical data monitoring system and a method thereof.
5
Hereinafter, this specification will describe the present invention according to the preferred
embodiment of the present invention. However, it is to be understood that limiting the
description to the preferred embodiment of the invention is merely to facilitate discussion of
the present invention and it is envisioned that those skilled in the art may devise various
modifications and equivalents without departing from the scope of the appended claims.
10
The following detailed description of the preferred embodiment will now be described in
accordance with the attached drawings, either individually or in combination.
Figures 1 shows a part of the preferred embodiment of a medical data monitoring system
15
(100), connectible over a network such that data is accessible via the network. The system
(100) includes a medical data recorder (103) connectible to a computing means by a
microcontroller (105) wherein the medical data recorder (103) further is connectible to a
plurality of skin electrodes (107), a data converter (109) wherein data from the medical data
recorder (103) is convertible into a transmittable data format in real time, wherein the
20
medical data recorder (103) further includes an amplifier, a filter and an analog to digital
converter. The medical data recorder (103) used in this preferred embodiment of the
invention is an electrocardiogram (ECG) recorder. A computing means is understood to be
selected from, but not restricted to, computers, laptops, tablets, palmtop devices, mobile
devices and netbooks.
25
The ECG recorder hardware that is used as a computer peripheral connected to the
computer via RS-232 port and software written to display the ECG data. The ECG recorder
5
can record single-lead ECG signal with properly placed three skin electrodes in this
embodiment. The ECG recorder hardware performs amplification, proper filtering and
analog-to-digital conversion to the ECG signal. The microcontroller (105) used in this
embodiment is an 8-bit microcontroller is used to control the hardware and to communicate
5
with the computer. The hardware is battery-powered and its design emphasises on low
power consumption. The ECG recorder is designed to be also used with hand-held
computers such as a palm top device with RS-232 port. The device is safe to use because it
is optically isolated from the 240V power line; thus, working independently in a robust and
reliable mode. The ECG signal was over sampled at 500 samples per second to improve its
10
fidelity.
The software was written in Visual C++ programming language. The software communicates
with the ECG recorder to control recording process, monitor battery status and display the
ECG signal in real-time while recording is in process with the indication of bad or good ECG
15
data. The software provides a graphical user interface (GUI), which help general user to
work with this system. Besides that, the system (100) detects presence of the heartbeat,
calculates current heartbeat rate and beat-to-beat interval while recording the ECG data in
memory. To make a reasonable file size for easy transmission over the Internet, a simple
form of Huffman’s lossless compression is performed to the ECG data before it is saved into
20
a file. The software includes the facility to send the recorded ECG file via e-mail as an
attachment together with the patient’s details, record date/time and duration.
The system is a low cost portable ECG device, international ECG standard compliance,
ease of use, output is comprehensibly readable by patients, portability, low power
25
consumption, storage of data, has data transmission facilities. The system further has a
sampling rate of 500 Hz and 12 bits sampling which is the medical standard, has a simple
GUI user interface with 3-leads ECG information with various types of viewing facilities and
related information (patient’s information, heartbeat, RR interval, zooming), battery operated
6
portable ECG device with international safety medical standards that comply with IEC601-1,
AAMI EC11 (protective class).
The system (100) has a loss less ECG Data Compression for convenient storage that
5
facilitates continuous ECG information collection for critical applications and/or stress test.
The system can be used as an Internet appliance device.
The system (100) is not a medical device, wherein the system (100) is a medical support
device (like thermometer to check fever at home). This system (100) will check the heart
10
condition prior to get advice from the professional doctor.
The ECG recorder includes a plurality of modules such as but not restricted to, amplifier,
filter, electrode guarding circuit, analog to digital Converter, power supply unit, Microcontroller (105), opto-isolator and RS-232 Transceiver. Peak value of the ECG signal at the
15
plurality of skin electrodes (107) is in the order of 1mV. The electrode-skin interface forms a
galvanic half-cell. The difference between the half-cell voltages of the electrode-skin
interface produces a voltage that usually varies slowly during a recording, resulting in a low
frequency noise. A cut-off frequency of 0.15 Hz for high-pass filtering is implemented to
eliminate the noise. To ensure correct operation with typical electrode-skin impedance and
20
typical interference sources, an amplifier was designed with very high common mode input
impedance (>100M at 50Hz), high differential mode input impedance (>10M at 50Hz), high
common mode rejection ratio (>80dB) and shielded input cables driven by a proper guarding
circuit.
25
The block diagram of the ECG recorder is shown in Figure 1. Three electrodes were used in
the ECG recorder in this embodiment, wherein two electrodes are used to sense the ECG
signal and the other one is for noise reduction. The weak ECG signal acquired from
electrodes is first amplified by the preamplifier with a gain of about 500 before it is filtered by
7
a 96Hz lowpass filter to eliminate most of the electromagnetic noise. The offset null circuit is
to eliminate the DC voltage between the two electrodes. The filtered signal is further
amplified to about 1V and the offset of the signal is shifted to 1.25V by another stage of
amplifier. It is necessary to shift the signal offset to 1.25V so that all the negative voltage is
5
shifted to positive because the ADC accepts pseudo-differential inputs ranging from 0V to
reference voltage of 2.50V. The amplified signal is digitized by a 12-bit ADC sampled at 500
samples per second before it is sent to the microcontroller (105) via 3-wire serial interface.
In Figure 1, there is shown a power supply unit that produces +5V and –5V needed by the
10
analog circuits. The power supply for analog circuit can be shut off by a control line
connected to the microcontroller (105). Besides that, the ECG recorder detects the battery
level and signals the microcontroller (105) in case of battery low. The ECG recorder has an
8-bit microcontroller to control its operations like initializing the ECG recording circle, stop
recording, shutdown the circuits when there is no activity and monitor the battery status. It
15
also implements the communication protocol between recorder and the computer. The ECG
recorder is physically isolated from the computer using opto-isolator for the safety of the
patient. This hardware design is in compliance with the international safety medical
standards IEC601-1, AAMI EC11 (protective class). The RS-232 transceiver is used to
convert the RS-232 signal level from the computer port to Transistor-Transistor-Logic (TTL)
20
level and vice versa. The system (100) of the ECG recorder hardware is powered by three
1.5V battery except the RS-232 transceiver, which is powered by the RTS line of the
computer port. The communication protocols between PC and the ECG recorder is
illustrated in Figure 2.
25
Figure 3 shows a preferred embodiment of a method of monitoring data over a connectible
network, wherein the data is accessible via the network. The method includes the steps of
detecting signals containing medical data,
compressing the medical data and
compressed data through the network in real time.
sharing the
8
Data flow diagram in Figure 3 shows the flow of information between different objects and
variables for the ECG recorder software. The object can be hardware, Graphic User
Interface (GUI), file on disk, variable in the program memory or running thread. The
information can be in the form of command or variable passed from one object to another.
5
The ECG software can communicate with the recorder hardware and get data from the
recorder. The recorded ECG signal can be displayed at five different scales, via 5mm/mV,
10mm/mV, 20mm/mV, 40mm/mV, and 80mm/mV. The P, Q, R, S and T waves of the
ECG signal can be clearly displayed at the scale of 10mm/mV, 20mm/mV, 40mm/mV, and
80mm/m. The recorded ECG signal has noise level of about 0.12mV and can be noticed
10
when displayed at the scale of 40mm/mv and 80mm/mV.
The method further controls the recorder hardware and gets the digitized ECG data from the
hardware via serial port. The method provides the display of the real time ECG signal,
patient’s heartbeat rate and the battery status when recording ECG. When viewing the
15
recorded ECG signal, the user can scroll through the signal by a scroll bar. Besides that, the
ECG signal can be zoomed to five different sizes. The method includes compressing the
ECG data before saving the data to a file and expands the data when the file is loaded. This
makes the ECG file small and easy to send through the Internet.
20
To support system (100) and the method and to realize its potential use, a web based
telemedicine data center can be vacillated. Where the user can open an account and upload
their ECG information regularly to the medical center for the doctor to analyze. This will
provide total freedom to the medical report handling and references. This web based
medical data center has various facilities, it also can be expand according to the hospital’s
25
requirements. The system (100) can be used with home care standard equipment, such as
glucose meter, BP device, weighing machine, and digital camera for patient’s medical data
preparation and storage in the telemedicine data center.
9
The system (100) and method allows for viewing the recorded ECG data in a convenient
way, wherein the system (100) has the real-time ECG signal viewing facilities with most
important function that indicating a proper ECG signal captured through displaying a vivid
blinking (red heart) symbol in the screen. This is very essential for the household and
5
general purpose applications, to know the ECG electrodes are placed correctly and the ECG
acquisition are accurate. In other ECG recorder development, the recorder has digital signal
processing (DSP) microprocessor to process the ECG signal. With the use of DSP
microprocessor, the ECG signal can be digitally filtered and it also allows real-time heart rate
determination. This type of recorder can send the ECG signal and heart rate to the computer
10
by radio link in real-time.
Because this type of device needs to continuously transmit the ECG signal and heart rate to
the computer, the power requirements are high, leading to short battery life. The system
(100) is a portable low power consumption device that works with the regular computer as
15
well as laptop and tablet PCs. The system will utilize the processing power and the display
facilities of a computer.
The Surface Electrodes
Surface electrodes are a class of sensor that acquires the naturally occurring bioelectric
20
signal such as ECG. They are placed in contact with the skin of the subject and it is called
Skin Electrode as seen in Figure 4. The electrodes for surface recording of biopotential are
generally made of silver-silver chloride (Ag-AgCl). With the system’s reusable metal-plate
electrode, and reusable suction cup electrode can be used to save the repeated cost of ECG
electrode. The normal one time used Ag-AgCl metal contact button at the top of a hollow
25
column that is filled with a conductive gel also can use. It is suitable to be used for long time
recording because it can hold well on the skin for long time.
10
Accurate ECG signal accruing
In most bioelectric measurements an interference level of 1 to 10μV peak-to-peak
(pp) or less than 1% of the pp value of an ECG, is acceptable.
5
Interferences of the ECG signal was handled in two ways which are common mode rejection
ratio and high common mode voltage into a differential input voltage, called “the potential
divider effect”. Consequently, a very high isolation mode rejection ratio is essential in an
isolated bioelectric recording. A high isolation mode rejection ratio can be achieved with
modern photo-optically isolation techniques (analog or digital) combined with a high gain
10
front-end. This feature has been used to omit isolation amplifiers with the medical
instrument’s safety standards (international safety medical standards that comply with
IEC601-1, AAMI EC11 (protective class).
An instrumental amplifier (IA) is suitable to be used as the preamplification of small ECG
15
differential signal as seen in Figure 5. The peak value of the ECG signal at the skin surface
electrodes is on the order of 1mV. To ensure correct operation with typical electrode skin
impedance and typical interference sources, an amplifier should meet the following
demands:
· Very high common mode input impedance (>100M at 50Hz),
20
· High differential mode input impedance (>10M at 50Hz),
· High common-mode rejection ratio (>80dB)
· Shielded input cables driven by a proper guarding circuit
Data Compression
25
In the case of ECG file, it is important to preserve the actual recorded ECG data when
transmitting to the physician for later analysis. Thus, the lossless compression technique is
more suitable to be used for the compression of ECG data. For Huffman coding, the actual
output of the encoder is determined by a set of probabilities.
11
When using this type of coding, a symbol that has a very high probability of occurrence
generates a code with very few bits by means of an algorithm in building a Huffman
decoding tree. The tree is then built with the following steps as seen in Figure 6:
· The two free nodes with the lowest weights are located.
5
· A parent node for these two nodes is created. It is assigned a weight equal to the sum of
the two child nodes.
· One of the child nodes is designated as the path taken from the parent node when
decoding a 0-bit. The other is arbitrarily set to the 1-bit.
· The previous steps are repeated until only one free node is left. This free node is
10
designated the root of the tree.
Heartbeat Detection Techniques
Accurate detection of R-peak of QRS complex is a prerequisite for reliable function of ECGanalysers. Recognition of almost all ECG parameters is based on a fixed point identifiable at
15
each cycle. R-peak is suitable for use as the datum point, because it has the largest
amplitude and sharpest waveform that can be extracted from ECG. The time and amplitude
measurements can be performed when the apex of the R-peak is detected at each cycle.
There are a numbers of ECG recognition algorithms used in ECG-analysers. Some are
based on different types of amplitude triggering, while the others examine the signal in the
20
frequency domain. The adaptive properties of algorithms to the changing signal may differ
and some algorithms use statistical methods for identification.
For the detection of R-peak, the amplitude level triggering method is based on the square of
the derivative. The high frequency components of an original signal are indicated by
25
differentiating the filtered ECG signal. The reliability of the identification is increased by
squaring this differentiated value, which will highlight the high frequency components. After
this processing, the R-peak can be detected by determining the known amplitude level as a
triggering level. The triggering level can also be adaptively determined. Thus, the value of
12
the triggering level is dependent on the upper values of the ECG signal. The differentiation
can be carried out by using the two, three and five point methods. The widely used algorithm
is the three-point method where the differential at instant n is calculated by dividing the
difference between n+1 and n-1 by the time interval (or time differential of the two samples)
5
between these two samples. The method can be further developed by increasing the
included time period and number of samples. The error and noise sensitivity of the
differentiation decreases when the number of
included samples increases,
but
simultaneously the accuracy is decreasing.
10
The R-wave triggering threshold value can be determined by trial and error to find out the
most suitable value. The value of the triggering threshold can adaptively change with the
base line value of the ECG signal as seen in Figure 8. The R-peak can be recognized by
determining the squared value that is greater than the R-wave triggering value. The current
RR-interval can be calculated by differentiating the previous R-wave time with the current
15
Rwave time and the heartbeat can be calculated by the following formula.
With health education’s dissemination through Internet, heath awareness has been
20
developed. This is the perfect time to introduce the system (100) at home for general
purpose uses. As ECG is a baseline test to check heart condition, and if ECG can be done
frequently without leaving home, then it is easy for a physician to identify a problem using
ECG history of a person.
25
There are interferences from different sources that disturb the ECG signal recording like the
13
main power supply, magnetically induced interference and the movement artefact. With
interference reduction techniques like proper grounding, driven right leg circuit, circuit
isolation, shielding of measurement cables, guarding circuit and proper signal filtering, the
interferences can be reduced to an acceptable level. Using in home will be no problem with
5
little precaution as normally done in hospital.
Any future design changes will be only to change the device’s firmware which is written in
assembly language. To transmit the ECG data through the Internet, the data compress
algorithm has been used to make the file size smaller for faster transmission. The lossless
10
compression should be used in the medical data exchange, thus Huffman coding was used.
The user’s ECG and the users information has been pasted in the same page with the
program, thus there are no chances of miss handling the data with users.
The system (100) can be used for cardiac research, cardiac rehabilitation, cardiac activities
15
follow-up (like Arrhythmia and Pacemaker), sports, emergency unit (wireless ECG transfer
through wireless Internet) as well as regular cardiac care for improving health. The system
can expand according to the organizational need. A hospital database can be developed
where the individual patient will upload their ECG information regularly from home for
diagnostic purposes.
20
This invention is adapted for use for use at home and for transmitting ECG data over
Internet. The disclosed invention is suitable, but not restricted to, for use as an Internet
medical appliance and as a portable ECG device.
25