Hi Hsiao-Lung Chan, Ph.D. Dept Electrical Engineering Chang Gung University, Taiwan

Transcription

1 Bioinstrumentation II Hi Hsiao-Lung Chan, Ph.D. Dept Electrical Engineering Chang Gung University, Taiwan

2 Cardiac cycle Pressures Heart sounds Systolic Diasystolic Bioinstrumentation 2

3 Circulatory system Systemic circulatory system Pulmonary circulatory system Systemic circulatory system Bioinstrumentation 3

4 Simplified circulatory system Deoxygenated blood CO 2 O 2 Upper body Oxygenated blood Tricuspid valve Right atrium Pulmonary valve Lung CO2 O 2 Left atrium Mitral valve Aortic valve Right ventricle Left ventricle Lower body CO 2 O 2 Bioinstrumentation 4

5 Heart sounds Analysis of the second heart sound to evaluate the stiffness of aortic valve Existence of systolic murmur means the aortic valve is stenosis Bioinstrumentation 5

6 Auscultatory areas Bioinstrumentation 6

7 Stethoscopes Mohrin, 1995 Bell mode two openings of the diaphragms coincide with each other Diaphragm mdoe No through opening Physicians i can change mode by pressing chestpiece against a patient s body and twisting the bell housing Bioinstrumentation 7

8 Stethoscopes (cont.) High-frequency sounds, or murmurs, are easier to hear with the diaphragm. The bell, which h should be applied lightly to the chest, transmits low-frequency sounds more Bioinstrumentation 8

9 Frequency response of stethoscopes Bioinstrumentation 9

10 Piezoelectric microphone v 1 C 1 1 t1 t 1 0 idt C 0 K dx dt dt K x C R Electrode C v o charge amplifier Highpass filtering: passes frequencies higher than the corner frequency c f = 1/(2RC). Bioinstrumentation 10

11 Blood pressure Bioinstrumentation 11

12 Extravascular blood pressure measurement Saline-heparin solution Bioinstrumentation 12

13 Strain-gage blood pressure sensor Plastic dome Armature Rigid frame Fluid couplings Cable Flexible diaphram Strain guages Bioinstrumentation 13

14 Strain guage displacement displacement l A ( l l) A stretched R ( l A l) stretched l A ( l l) la 2 l A ( l 2 2ll l Al 2 l 2 ) R 2l A 2l l R Bioinstrumentation 14

15 Wheatstone bridge circuit Bioinstrumentation 15

16 Cardiac catherterization Bioinstrumentation 16

17 Cardiac catherterization (cont.) Aided by x-ray equipment Measure pressures within each chamber of the heart and across the valves. Measure cardiac output Measure oxygen concentration across valves and walls (septa) of the heart Coronary arteries can be viewed by injecting dye or opened using balloon angioplasty Bioinstrumentation 17

18 Pressure gradient Bioinstrumentation 18

19 Intravascular sensors Detection of pressure in the catheter tip without the use of liquid-coupling system High-frequency response Eliminate time delay Bonding strain-gage systems onto a flexible diaphragm at catheter tip Temperature and electric drift, fragility, nondestructive sterilization Expensive Fiber-optic microtip sensor Bioinstrumentation 19

20 Fiber-optic pressure sensor Coupling between source and detector is a function of overlap of two acceptance angles on the membrane can be used for magnetic resonance imaging Bioinstrumentation 20

21 Fiber optics Snell s law n 2 sin2 n1 sin 1 Refraction of rays that escape from wall of fiber Low refractory index High refractory index n 1 =1.62 for a glass Internal reflection within a fiber 3 : accepted angle for internal reflection in fiber when n 0 1 sinic n2 sin 90 n 2 Bioinstrumentation 21

22 Indirect blood pressure measurement Bioinstrumentation 22

23 Indirect blood pressure measurement Cuff Occluded blood vessel ( Korotkoff sounds ) Bioinstrumentation 23

24 Bioinstrumentation 24

25 Continuous noninvasive blood pressure measurement (NIBP) Arterial tonometer Bioinstrumentation 25

26 Continuous NIBP IEEE Engineering in Medicine and Biology Magazine, 2005 Bioinstrumentation 26

27 Continuous NIBP (cont.) IEEE Engineering in Medicine and Biology Magazine, 2005 Bioinstrumentation 27

28 Reference JG. Webster, Medical Instrumentation, t ti application and design, 3rd, Houghton Mifflin, JJ.Carr, JM.Brown, Introduction to Biomedical Equipment Technology, 4nd Edition, Prentice-Hall, S. Franco, Design with Operational Amplifiers and Analog Integrated Circuits, Second Edition, D. Prutchi and M. Norris, Design and Development of Medical Electronic Instrumentation: A Practical Perspective of the Design, Construction, and Test of Medical Devices, John Wiley & Sons, 生物醫學工程導論, 滄海書局,2008.