Electromyogram (EMG) Hsiao-Lung Chan Dept Electrical Engineering Chang Gung University

Transcription

1 Electromyogram (EMG) Hsiao-Lung Chan Dept Electrical Engineering Chang Gung University

2 Skeletal muscle: Sarcomere (basic unit of skeletal muscles) ( 肌小節 ) ( 肌蛋白 ) (Actin attached on Z line) ( 肌動蛋白 ) J. Enderle, Introduction to Biomedical Engineering, Academic Press, HL Chan, EE, CGU EMG 2

3 Origins of electromyography HL Chan, EE, CGU EMG 3

4 Action potential of motor unit Afferent nerve 感覺神經 肌肉 傳輸神經 Efferent nerve Muscle HL Chan, EE, CGU EMG 4

5 Motor unit action potential HL Chan, EE, CGU EMG 5

6 Motor unit recruitment A single motor unit firing at 8 Hz at a low level of muscle contraction Recruitment of a second motor unit results in a gradual increase in strength and firing rate Further increased by the recruitment of a third motor unit HL Chan, EE, CGU EMG 6

7 Electrode for EMG measurement Percutaneous electrode Transcutaneous electrode Subcutaneous electrode

8 Motor-unit firing pattern SMUAP wave y( t) h( t ) x( ) d t 0 IPI Point process: A series of impulse or Dirac delta function Inter-pulse interval (IPI) > SMUAP duration R. Rangayyan, Biomedical Signal Analysis, John Wiely & Sons, HL Chan, EE, CGU EMG 8

9 Electromyography (EMG) Resting state Muscle contraction HL Chan, EE, CGU EMG 9

10 MUAP Normal: Mostly biphasic, 3-5 ms duration Neuropathy (brachial plexus in injury): Slow conduction Polyphasic, large amplitude (800 V) Myopathy: Loss of muscle fibers in motor unit Recruitment of more motor units at a low level of effort HL Chan, EE, CGU EMG 10

11 Gradation of muscular contraction Spatial recruitment Activating new motor units with increasing effort Temporal recruitment Increasing frequency of firing rate of each motor unit with increasing effort EMG at diaphram muscle HL Chan, EE, CGU EMG 11

12 Gradation of muscular contraction (cont.) SMUAPs at initial stages of contraction, following by increasing of several MUAP HL Chan, EE, CGU EMG 12

13 Prosthetic Control Using Myoelectric Signals A prosthetic arm that "feels" The Center for Bionic Medicine at the Rehabilitation Institute of Chicago

14 Arm amputations

15 Body-powered prostheses Squish your shoulders It pulls on a bicycle cable The bicycle cable can open or close a hand or a hook or bend an elbow.

16 Bionics The science of replacing part of a living organism with a mechatronic device or a robot.

17 Myoelectric prostheses Motorized devices controlled by electrical signals from your muscle Several robotic limbs available on the market Open and close of a hand A wrist rotator Vari-grip ability

18 Myoelectric control system at University of New Brunswick, Canada

19 Myoelectric control system (cont.)

20 How does the body work? Motor control Starting a motor command in brain, going down spinal cord, out the nerves and to periphery. Sensation is opposite.

21 Connect to nervous system or thought processes: intuitive and natural It's really hard to record from little tiny individual neurons. They are microvolt signals!

22 Myoelectric prostheses in the Rehab Institute of Chicago Using a biological amplifier (muscles) to amplify nerve signals Take the nerve away from chest muscle and let nerves for arms grow into it.

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24 Targeted reinnervation Now you think, "Close hand," and a little section of your chest contracts. You think, "Bend elbow," a different section contracts.

25 Targeted reinnervation patients Jesse Sullivan 1 st targeted reinnervation patient Amanda Kitts, patient and research collaborator

26 More degrees of freedom in control a robotic arm Up to 10 different degrees of freedom hand closed and open wrist flexion and extension elbow that goes up and down shoulder joints movable hands.

27 SENSORY REINNERVATION (GIVE BACK SENSATION) After a few months, a patient he felt his missing hand when touching his chest. He feels his thumb or pinky. He feels light touch down to one gram of force. He feels hot, cold, sharp, and dull. Imagine sensors in the prosthetic hand coming up and pressing on this new hand skin. He might feel the touches in his prosthetic hand.

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29 Reference Leif Sörnmo, Pablo Laguna, Bioelectrical Signal Processing in Cardiac and Neurological Applications, Academic Press, John Enderle, Susan Blanchard, Joseph Bronzino, Introduction to Biomedical Engineering, Academic Press, John G. Webster, Bioinstrumentation, John Wiley & Sons, John G. Webster, Medical Instrumentation, application and design, 3 rd Ed., Houghton Mifflin, BH.Brown, RH.Smallwood, DC.Barber, PV.Lawford, and DR.Hose, Medical Physics and Biomedical Engineering, IOP Publishing Ltd, Joseph J. Carr, John M. Brown, Introduction to Biomedical Equipment Technology, Pearson Education, 2000.