자기공명 임피던스 단층촬영 기술 연구센터 $MREIT Research Center$

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1 생체임피던스의계측 (Bompedance Measurements) 경희대학교전자정보학부동서의료공학과우응제

2 목차 생체임피던스의기전 전극 전해질 피부인터페이스 생체임피던스측정시스템 전극사용법 전극법 4 전극법 전극법 발진회로 정전류원 전압측정법 전기안전및전원 체지방의계산 참고자료

3 Overvew Cell Tssue Organ Subsystem Body Abnormal Dagnoss Normal Abnormal Property Status Functon Metabolsm Interacton Chemcal Mechancal Thermal Electromagnetcal Acoustcal

4 Bologcal Sgnals Sgnal ECG EEG EMG Blood Pressure Blood Flow espratory ate espratory Gas Flow Blood Gas Bompedance Ampltude µv 5 mv 5 µv µv mv 4 mmhg ml/s 5 bpm 6 l/m. mmhg 5 kω Frequency.5 Hz.5 Hz, Hz dc 5 Hz dc Hz. Hz dc 4 Hz dc Hz dc 5 Hz

5 생체신호의특징 측정대상이인체 측정량 크기가작다 주파수가낮다 센서접속 Invasve Nonnvasve 부시스템간의간섭 많은부궤환 미지의상호작용 측정변수의분리불가능 Stochastc Tmevaryng Nonlnear Large varablty Safety standard Clncal envronment 동물 / 임상실험 인증

6 Overvew: Instrumentaton External Energy Electrcal Isolaton Informaton Technology Sgnal Measurand Sensor Output Processng Analog Technology Dgtal Technology

7 Volume Conductor Feld Source: Heart or Exctaton Equpotental Lnes Tssue esstvty (Ωcm) Lead Φ = H m 최소값최대값 체액혈장 혈액 근육 ( 횡방향 ) 간 팔근육신경조직심장근육근육 ( 종방향 ) 폐지방 뼈 Geometry Materal property Source

8 Forward and Inverse Problem Forward Problem Φ = : ( σ ) m Inverse Problem Φ Boundary Measurements Measurement or Numercal Computng Modelng and Estmaton Φ : Forward m : Surface Sgnal Processng/Analyss Inverse Interor Source Localzaton Tssue Characterzaton

9 저항률 (esstvty) 의측정 F = qe E v J = µ E = σ E q. b V = EdL = EL a I V J = = σ E = σ S L L L V = I = ρ I = I σ S S S σ = ρ L E

10 생체조직의저항률 ( ~ khz) Tssue Cerebrospnal flud Plasma Blood Lver Human arm Skeletal muscle Cardac muscle Neural tssue Lung Fat Bone esstvty (Ωcm) ~ 55 4 (longtudnal), 675 (transversal) 5 ~ 5 (longtudnal) 8 ~ (transversal) 6 ~ 575 (longtudnal) 44 ~ 58 (transversal) 58, 84 (gray matter), 68 (whte matter) 77 ~ 6 6 ~ 7 66 John G. Webster, Electrcal Impedance Tomography, Adam Hlger, 99

11 Sensor: Electrodes Ionc Current Electronc Current Converson of Charge Carrers ElectrodeElectrolyteSkn Interface Amplfer Skn Model John G. Webster, Medcal Instrumentaton: Applcaton and Desgn, rd. ed. P. W. Macfarlane and T. D. V. Lawre, Comprehensve Electrocardology

12 전극사용법 TwoElectrode Method 접촉저항의영향포함 FourElectrode Method 접촉저항의영향제거 ThreeElectrode Method 접촉저항의측정

13 Bompedance Measurement System Oscllator VI Converter Electrode Electrode Hgh stablty Low THD Hgh lnearty Hgh source resstance Voltage complance Electrode Electrode Instrumentaton Amplfer (ac, low gan) BPF & Demodulator nd Amplfer & LPF Level Shfter ADC Hgh nput mpedance Optmal gan Low output mpedance Optmal bandwdth Hgh CM Optmal dynamc range Hgh SN Patent solaton John G. Webster, Medcal Instrumentaton: Applcaton and Desgn, rd. ed.

14 Waveform Generator Analog Oscllator WenBrdge Oscllator Dgtal Waveform Generator OMAddress GeneratorDACBPF TmerDgtal Output Performance Ampltude Stablty Frequency Stablty THD (Total Harmonc Dstorton)

15 WenBrdge Oscllator Basc WenBrdge Oscllator Practcal WenBrdge Oscllator Vp C C.8k p C ua74 7 V V 4 U Vcc OS 5 6 OS Vcc Vo C p.8k 7 V V 4 5V U OS OS 5V ua k 발진주파수 : f = π C 발진조건 : / = 4 k 6 k D DN448 D4 DN448 Ampltude Stablty <.6% THD <.4%

16 WenBrdge Oscllator wth AGC AGC usng Precson ectfer, LPF, and JFET C C p.8k.8k 5V U LM8 J 4 7 V V 4 C 5V k C C 5 8.k 7 6 {var} BC64C 6.8k 6 8 C p C 5 6.8k p 6 k 4 k 8 47k k 5.6k V V C C C U 5V 5 C C5 7 4 V V C C 5V 68p D DN448 u 5V U LM V LM8 C6 D DN448 C4 u.k 5V 4.7k 9 C p.8k UA TL84 4 V V p 5V 5V k 4 5k 5 k J JN486.8k 6 k k D DN448 UB 5V TL84 D 7 DN448 5V 9 k C 4 4 V V u 5.9k 4 V V UD 5V TL84 5V 8 k 5V 9 5V 4 V V UC TL84 8 Ttle <Ttle> Sze Document Number 5.9k Ampltude Stablty <.6% THD <.% Ampltude Stablty <.% THD <.68%

17 Constant Current Source () t s () L t (t) s L v L () t Hgh Source Impedance ange of Load Impedance for Lnear Operaton Voltage Complance

18 VI I Converter (A and B) Vs 4 4 U 6 Vx Vo L L Vs 4 U5 HA6 5 7 V V B COMP B L L = 조건 : 출력전류 : 4 L = 4 V s = 조건 : 출력전류 : 4 L = 4 V s

19 VI I Converter (C and D) Vs 4 4 Vo U 6 6 U Vy HA6 x L L 6 V f Vs 6 U U 6 6 U (VfVs) V I L 조건 : 출력전류 : = = = 4 L = x V s 조건 : 들의 matchng 출력전류 : L = V

20 Selecton of VI V I Converter 정전류원으로동작하는부하의범위 Tunng이필요한소자의수 Voltage complance ( 출력전압의허용범위 ) 출력에서 transformer 또는 capactve couplng 사용 주입전류의크기는 5kHz에서. ma 이내 주입전류의크기는작을수록좋음 주입전류의크기가작으면 SN이낮아짐

21 AC Instrumentaton Amplfer SIG() SIG() JP JP JUMPE JP JP4 JUMPE 5V 8 V V 4 5V 5v 8 4 V V 5v U8A TL8 UA TL8 C P C8 p k 5 k C n C6 n C9 n V V 5v 5v 5V V 5V 6 U9A TL8 5V V 5V C5 p AMP_ Dfferental Amplfer Very Small Input Current Hgh CM: onechp IA 고려 ( 예 : AD6) IA 출력단에서 BPF 사용고려

22 Demodulator ACDC Converter Precson ectfer LPF Ampltude Measurement PhaseSenstve Demodulator Analog Multpler or Swtchng Devce (AD6) LPF Inphase and Quadrature Measurement

23 LPF, ADC, and Calbraton LPF Cutoff Frequency, Order, Settlng Tme Example SIG.6k C.7u.6k 5V TL8 C.7u U9A 8 4 V V 5V C5 P.4k C.9u 4.6k 5V TL8 C4.u UA 8 4 V V 5V C6 P A/D_IN ADC Input ange, esoluton Averagng Calbraton Overall Gan n V/Ω esstor Phantom:. kω Compensaton usng a Calbraton Curve Keep Constant ElectrodeSkn Contact Area

24 Power Supply and Electrcal Safety Patent Isolaton Transformer Couplng Optcal Couplng Power Supply Medcal Grade Safety Analyzer

25 TBW and FFM H S ρ V H = ρ S = SH = H ρ H: heght W: weght V: volume Total Body Water (TBW): TBW TBW H = α α H = α αw α Fat Free Mass (FFM): FFM = TBW.7

26 체지방지수의계산 기본변수 : 신장 (H), 몸무게 (W), 임피던스또는저항 () 추가변수 : 나이 (A), 성별 (S) Body Fat (BF): ( W FFM) H BF(%) = = ( β ) W W H BF(%) = β βa βs β4 W

27 부분별생체임피던스의계산 x x x x4 x5 Segment 들이접촉되지않는측정자세유지 x x = r x x x4 = r x x x5 = r x4 x5 = r4 x x x5 = r5 x x x4 = r6 r x r x r x = r4 x4 r5 x5 r 6 Ax = r Least Square Soluton r x r x r x = r4 x r5 x r6 ( T T x = A A) A r

28 체지방지수의계산 기본변수 : 신장 (H), 몸무게 (W), 임피던스또는저항 (x ) 추가변수 : 나이 (A), 성별 (S) Body Fat (BF): H BF(%) = ( β β β ) β A β S β W arm trunk leg arm = xx x x trunk = x leg = x x x 4 5 x 4 5

29 참고자료 US Patent #4,895,6 (//99): Lbke US Patent #5,8,49 (/8/994): Wthers US Patent #5,5,667 (9/9/994): Cha US Patent #5,7,4 (//994): Gallup US Patent #5,45,76 (5/6/995): Sato US Patent #5,449, (9//995): Lbke US Patent #5,6,5 (/8/997): Sato US Patent #5,65,689 (4//997): Kotler US Patent #5,7,96 (/4/998): Cha 대한민국특허제 48 호 (4//996 공개 ) 등 J. G. Webster (ed.), Medcal Instrumentaton: Applcaton and Desgn, rd. ed., NY, John Wley & Sons, 998 J. G. Webster, ed., Electrcal Impedance Tomography, Brstol, UK, Adam Hlger, 99 S. Grmnes and O. G. Martnsen, Bompedance and Boelectrcty Bascs, London, UK, Academc Press, J. P. elly, Appled Boelectrcty, NY, Sprnger, 998 AAMI, Safe Current Lmts for Electromedcal Apparatus (ANSI/AAMI ES), Arlngton, VA, AAMI, 99 S. Franco, Desgn wth Operatonal Amplfers and Analog Integrated Crcuts, nd ed., NY, McGrawHll, search wth boelectrc mpedance analyss

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자기공명 임피던스 단층촬영 기술 연구센터 \(MREIT Research Center\)