DSP Applications in medical field:Hearing aid, ECG, Blood pressure monitor. Noise filtering,Fast fourier transform and Bandpass & FIR filter on matlab.

1. DSP APPLICATIONS
IN
MEDICAL FIELD

2. What's
DSP?

3. DIGITAL SIGNAL PROCESSING
Digital signal processing (DSP) is the
process of analyzing and modifying a
signal to optimize or improve its efficiency
or performance. It involves applying
various mathematical and computational
algorithms to analog and digital signals to
produce a signal that's of higher quality
than the original signal.

4. ADVANTAGES OF DSP
DSP
Securing Data
Store Signals in
Digital Format
for Analysis
Extraction of
Signal from Noise
Compress Data

5. DSP IN MEDICAL FIELD
APPLICATIONS
Hearing aid Blood pressure
monitor
ECG

6. HEARING
AID
• A hearing aid is a small electronic device that
you wear in or behind your ear. It makes
some sounds louder so that a person with
hearing loss can listen.
• Hearing aids are primarily useful in improving
the hearing and speech comprehension of
people who have hearing loss that results from
damage to the small sensory cells in the inner
ear, called hair cells.

7. HEARING AID
How does it
work?• The sound is picked up by the microphone, is converted into an
electric signal, and then digitized.
• The digital signal is then filtered to selectively amplify those
frequency bands in which the patient shows the most severe hearing
loss.
• Amplitude compression, in which the system gain is reduced when
the amplitude exceeds some pre-defined threshold values, in order
to avoid excessive loudness to the ear is also used.
• Finally the processed digital signal is converted back to analog form
in the digital-to-analog (D/A) converter, and delivered to the ear via
the earphone.

8. Sound
Analog
signal
Microphone
( A/D
Converter)
Digital
signal
Variable
Bandwidth filters Digital
signal
Filtered
Amplifier
Amplitude
compression
Amplified
Filtered
Digitalsignal
Digital
signal
DesiredD/A
ConverterAnalog
signal
Desired
EarphoneEar

9. Blood pressure monitor
Blood pressure monitors can use Korotkoff,
Oscillometry, or Pulse Transit Time methods to
measure blood pressure. They employ a pressure cuff,
pump, and transducer to measure the blood pressure
and heart rate in three phases: Inflation, Measurement,
and Deflation. They include an LCD, memory recall,
selection buttons, power management, and USB
interface.

10. Blood pressure monitor

11. • The pressure transducer produces the output voltage proportional to the applied
differential input pressure. The output voltages of the pressure transducer range from 0 to
40 mV, which needs to be amplified so that the output voltage of the DC amplifier has a
range from 0 to 5V. This is why, we need a high-gain amplifier. Then the signal from the
DC amplifier will be passed on to the band-pass filter. The DC amplifier amplifies both DC
and AC component of the signal.
• The filter is designed to have large gain at around 1-4 Hz and attenuate any signal that is
out of the pass band. The AC component from filter is important for determining when to
capture the systolic/diastolic pressures and heart rate of the patient. The final stage of the
front end is an AC coupling stage, after which the signal is sent to analog to digital
converters, and digitized.
• The digital measurements of pressure and heart rate are performed by the
microprocessor. Measurements results are stored in EEPROM or FLASH memory as a
data log that can be uploaded to a PC via USB. The analog circuit is used to amplify both
the DC and AC components of the output signal of pressure transducer so that we can use
the MCU to process the signal and obtain useful information about the patient’s health.
Blood pressure monitor

12. Input
Pressure Pressure
Transducer Electrical
Signal
Amplifier
Amplified
Analog Signal
Band Pass
Filter
1-4 Hz
Signal
Filtered
A/D
Converter
Micro
processor Digital
Signal
PC
Stored
DataResult

13. ECG
An electrocardiogram (ECG) is a graphical
record of bioelectrical signal generated by
human body during cardiac cycle.
ECG graphically gives useful information that
relates to the heart functioning and detecting
heart disease by means of a base line and
waves representing the heart voltage changes
during a period of time, usually a short period.

14. ECG
How does it
work?ECG records the electrical activity generated by heart muscle depolarizations, which
propagate in pulsating electrical waves towards the skin. Although the electricity amount is in
fact very small, it can be picked up reliably with ECG electrodes attached to the skin (data unit:
microvolt, uV).
The electric signal gets sent to Amplifier and bandpass filter to pass certain needed
frequencies then extract 60 Hz noise signal from electric signal.
The filtered signal Pass through A/D converter then microcontroller to process the signal .
The output signal reading can be shown in the PC monitor or compressed in a SD memory.

15. Block Diagram of how ECG works

16. BAND PASS FILTER
A bandpass filter is an electronic device or
circuit that allows signals between two
specific frequencies to pass
What’s Bandpass filter?

17. FOURIER TRANSFORM OF SIGNAL WITH NOISE IN
ECG
What’s Fourier Transform?
The Fourier transform (FT) decomposes a
function of time (a signal) into the
frequencies that make it up
Fast Fourier transform
Discrete of fourier transform that samples
over a period and divides it into frequency
components

18. FILTERING NOISE

20. BAND PASS FILTER

22. FOURIER TRANSFORM OF SIGNAL WITH NOISE IN
ECG

23. Signal & Noise in time domain before doing fourier
transform

24. Signal & Noise in frequency domain after doing fourier
transform

25. Comparison between Signal with and without noise in time
domain and frequency domain

26. FIR FILTER TO REMOVE 60 HZ NOISE

27. Voltage with 60Hz noise in Time domain
Applying FIR filter to remove noise
in frequency domain

28. Comparison between unfiltered and
filtered signal from 60 Hz noise

29. THANK
YOU!