Time - frequency Analysis Applied Time - frequency Analysis Applied To Biomedical SignalsTo Biomedical Signals

Hiew Yen HaHiew Yen Ha

Supervisor: Dr. Barry Cheetham

Advisor: Mr David Tait

ContentsContents

Participants. Motivation. Aims. Types of biomedical signals.

Participants. Motivation. Aims. Types of biomedical signals. Intro

Recording system. Database. Physiology of cough. Cough analysis. De/Compression.

Gold Standard cough counting technique.Software Version-MCA101, 401 & 801.

Recording system. Database. Physiology of cough. Cough analysis. De/Compression.

Gold Standard cough counting technique.Software Version-MCA101, 401 & 801.

Year 1 Work

Results of Gold Standard Vs software.

Conclusion.

Results of Gold Standard Vs software.

Conclusion.

Preliminary Results

Additional goalsAdditional goalsFuture Works

IntroIntro

Participants

North West Lung Centre, Wythenshawe Hospital

Aintree Chest Centre, University Hospital Aintree

Dr. John Earis

Prof. Ashley Woodcock Dr. Jackie Smith

IntroIntro

Types of biomedical

signals

Cough signals

•Asthma

•Cystic Fibrosis (CF)

•Cryptogenic Fibrosing Alveolitis (CFA)

~ Factors: allergy, airborne irritants, infection & weather change.

~ Airways clogged by mucus & swelling, causing difficulty to breath in and especially out.

~ Genetic disorder (usually Caucasian).

~ Affects mucus-secreting glands, interfering with lung function & digestive system.

~ Possible factors: cigarette smoking, exposure to metal, wood & coal dust.

~ Associated with fibrosing pulmonary and alveoli inflammation

IntroIntro

Motivations (I) Study of lung diseases by investigating pathological

vocalisation - cough sound analysis

(II) Application of wavelet analysis

(III) Objective long-term cough monitoring

~Euro. Resp. Jr 1999 13:1447-1450• Used in cough challenge methodology

• Wavelets useful for time-frequency analysis of non-stationary signals. According to R.A.L.E., application of wavelets to coughs is new.

• Although much research in cough challenge methodology, air-flow & volumetric variations of lungs, & lung sounds analysis has been done in the past, little work has been done on the acoustic analysis of cough.

• Objective measurements of cough more reliable than subjective descriptions from doctors or patients. ~ Arch.Dis.Child 2001 84:31-34

IntroIntro

Aims Software package with functions of...

Cough recognition Counting & measurement

• Discrimination from background noise

• Number of coughs per unit time

• Long term distribution with time

• At least 80% accurate

Year 1 WorkYear 1 Work

Recording system

c L

R

A C

L a p e lm ic ro p h o n e

T h ro a tm ic ro p h o n e

S o u n d s o u rc e

A m p lifie r

L L e ft c h a n n e l

R R ig h t c h a n n e l

A C A lte rn a tec u rre n t

D .A .P .J u k e bo x pla y e r

L E G E N D

Fs: 16K Hz

Format: Wav format, stereo type

Recording: Tracks (30 min) -112,512KB

selectselect

Year 1 WorkYear 1 Work

Database

Asthma

8 recordings with mean duration of 8 hr

C.F.

11 recordings with mean duration of 9.5 hr

C.F.A.

9 recordings with mean duration of 10 hr

All-night recordingsAll-night recordings

Year 1 WorkYear 1 Work

De/compression

Compression & Decompression

•Size of each 30-min track is 112MB.

•Compression program eliminates silent periods & compresses the file without affecting the information.

•Decompression program reconstructs the original files.

Year 1 WorkYear 1 Work

Physiology of cough

A respiratory reflex thatrid noxious substances from the lungs.

What’s a cough?

Acute cough = cough < 3 weeks, Chronic cough = cough > 3 weeks.Cough Mechanics

Inspiratory cough phase

Compressive cough phase

Expiratory cough phase

•Take 1 sec.

•Deep inspiration

•Glottis firmly closed.

•Closure of the glottis.

•High intra-thoracic pressure.

•Glottis opens, followed by a high expiratory flow rate. The pressure of the central airway falls rapidly.

•Cough sounds = Excitation phase + mid-noisy phase.

0 2000 4000 6000 8000 10000 12000-3

-2

-1

0

1

2

3x 10

4

Amplitude

sample

Excitation phase

mid-noisy phase

Year 1 WorkYear 1 Work

Cough Analysis

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2

x 104

-3

-2

-1

0

1

2

3x 10

4

Amplitude

sample

1st cough sound 2nd cough sound

1 breath

Cough Effort

Excitation phase & Mid-noisy phase

Year 1 WorkYear 1 Work

Cough Analysis

0 0.5 1 1.5 2 2.5 3 3.5

x 104

-4

-3

-2

-1

0

1

2

3

4x 10

4

AsthmaAsthma

0 100 200 300 400 500 600 700-4

-3

-2

-1

0

1

2

3

4x 10

4

Year 1 WorkYear 1 Work

Cough Analysis

0 0.5 1 1.5 2 2.5

x 104

-4

-3

-2

-1

0

1

2

3

4x 10

4

C.F.C.F.

Year 1 WorkYear 1 Work

Cough Analysis

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2

x 104

-4

-3

-2

-1

0

1

2

3

4x 10

4

C.F.A.C.F.A.

Year 1 WorkYear 1 Work

Gold Standard

•Identify & count coughs.

•Eliminate background noise.

•Count cough sounds instead of cough effort.

MCA101, 401MCA101, 401

MCA801MCA801• Identify “positive cough moments” (PCM).

• PCM = 1 sec frame that contains coughs.

• Count PCMs in each file.

Manual assessment by qualified clinician.

Year 1 WorkYear 1 Work

Software

MCA101MCA101

~ Automatically identify & count cough sounds.

~ Early version.

~ Not suitable for overnight recordings.

MCA401MCA401

~ Automatically identify & count cough sounds.

~ Not suitable for C.F. and C.F.A.

~ Developed for overnight recordings.

MCA801MCA801

~ Automatically Identifies & counts PCMs.

~ Designed to work for asthma,C.F., & C.F.A.

~ Suitable for overnight recordings.

Jan-Aug 2001Jan-Aug 2001

01020304050

12:0

0 A

M

1:0

0 A

M

2:0

0 A

M

3:0

0 A

M

4:0

0 A

M

5:0

0 A

M

6:0

0 A

M

7:0

0 A

M

8:0

0 A

M

9:0

0 A

M

Program

Program

Gold Standard

Cough measurement of program Vs Gold Standard

No. of cough sound

Time

JE RecordingJE Recording Date : 7 June 2001

(JM020 Track007) Gold Standard count VS Program count (PCM)

36

10

20

29

23

19

4

1720

17

41

12

16

26

21

17

4

34

28

20

0

5

10

15

20

25

30

35

40

45

3 min block

Nu

mb

er

of

po

sit

ive

co

ug

h s

ec

program count Jacky's count

program count 36 10 20 29 23 19 4 17 20 17

Jacky's count 41 12 16 26 21 17 4 34 28 20

3 6 9 12 15 18 21 24 27 30

Validation of MCA801

Year 1 WorkYear 1 Work

Conclusion

• Cough recognition & counting software tested on 3 types of disease.

• Version 401 meets spec. for asthma, but not for C.F. & C.F.A. coughs.

• Version 801 still to be validated against “gold standard”.

• Recognition algorithm needs to be refined.

• “Gold standard” is questionable reference & needs further consideration.

Research IssuesResearch Issues

•Identifying characteristics of coughs & relating these to physiology.

(e.g. why does asthmatic coughs have a periodic onset?)

•Cough identification & elimination of background noise.

•Advantages of wavelets for cough analysis (coughlets!)

•Devising objective measures for frequency & time distribution of events.

•Presentation of measurements.

•Mobile technology for remote monitoring.

ApplicationsApplications

(1) Portable 24 hr cough monitoring.

(4) Assessment of effectiveness of anti-tussive drugs.

(5) Medical research into nature of cough.

(2) Recognition of types of pathological cough sounds.

(3) Detect difference between healthy & pathological cough.

~DSP techniques applied to study of characteristic of coughs & related lung diseases.

~ The long term measurements can be used to compare the effectiveness of drugs.

~ Diagnostic tool.

~This type of software (enhanced) is capable of recognising types of pathological cough.

~ So far only over-night recordings made. Higher cough frequency during day.

More background noise to contend with and technology problems to address.