DSP applications in medical field.

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 Digital signal Digital signal Desired D/A Converter Analog signal Desired Earphone Ear

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 Data Result

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

19. Band Pass filter

20. Fourier Transform of Signal with noise in ECG

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

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

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

24. FIR filter TO REMOVE 60 Hz Noise

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

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

27. THANK YOU!