Medical Signal Processing

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Medical Signal Processing

• Massimo Mischi
• Quantification of ultrasound contrast agents
• Neuromuscular conditioning

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Ultrasound Contrast Agents (UCA)

• UCA are microbubbles with a diameter from 0.1 to
  10 ?m.
• They are made of an inert gas enclosed in a
  phospholipidic, albumin, or polymer shell.
• When invested by US, they scatter energy with a
  nonlinear behavior.

Electron microscopy 13500?
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UCA quantification
Nonlinear behavior of contrast agents
linear behavior of tissue
Nonlinear contrast imaging techniques
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UCA quantification
Requirement Linear or known relationship between
measured acoustic intensity and UCA concentration.
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Unexpected artifact
Fundamental (linear) imaging
Harmonic (nonlinear) imaging
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Nonlinear US distortion
1st hypothesis effects of nonlinear propagation.
Increasing distance from source
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Forward scattering model
It is more complex than expected

• Forward scattering model
• Derived from dynamic bubble behavior using the
  modified RPNNP1 equation
• Combined with the non-homogeneous wave equation

de Jong (1993)
Zabolotskaya Soluyan Sov Phys Acoust, 1973
1 Rayleigh-Plesset Noltingk Neppiras and Porisky
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Implementation

• Forward scattering model
• Finite difference in time domain
• Combined with the modified
• RPNNP equation for the bubble
• radius dynamics

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Measurement setup
Latex tube with saline-UCA dilution
Acoustic absorber (sponge)
Water filled basin
A/D converter PC
Pulse generator RF Amplifier
Focal zone transmitter (7.1cm)
Transmitting single element US transducer
(Panametrics, 2.25MHz)
Receiving hydrophone/ Amplifier (Onda HGL-0400/
Onda AH-2010-025)
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Measurement setup

• Transmission of 16-cicle sine-wave pulses (0.5 to
  and 3.5 MHz)
• Low pressure (MI 0.1)
• Definity concentrations 0-300 µL/L
• Sampling frequency 100 MHz

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Results
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Results
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Neuromuscular conditioning
Dedicated Lab (room PT 5.32) for prototyping and
measurements

• Applications
• Sports,
• Rehabilitation,
• Prevention of injuries
  or diseases,
• Esthetics.

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Prototyping
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Prototyping
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Expected advantages

• Strong reduction of effort and risks
• Lower joint stress and damage
• Additional benefits
• increase of

• Neuromuscular control and muscle co-activation
• Bone density
• Oxygen glucose uptake

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sEMG measurement

• Isometric contraction of
• - biceps (arm flexion )
• - triceps (arm extension)
• 2 pairs of differential electrodes on biceps
  brachii and triceps muscles.
• Isometric contractions (flexion extension) of
  10 s at 20, 40, 60, 80, and 100 of MVC.
• With and without 28-Hz force modulation (FM).

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Motion artifact suppression
Removal of motion-artifact harmonics from the
frequency spectrum with adjustable filters.
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Results (hyperactivation)
M. Mischi and M. Cardinale, Medicine Science in
Sports Exercise, in press.

Triceps normalized activation



Biceps normalized activation
plt0.05
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Results (co-activation)
M. Mischi and M. Cardinale, Medicine Science in
Sports Exercise, in press.
Arm extension biceps/triceps activation
Arm flexion triceps/biceps activation


plt0.05
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Ultimate goal
Dynamic feedback control
control unit
actuator
body
Input setting
sensors
signal processing
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Further sEMG signal analysis
Motor Unit Action Potential (MUAP)
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Future developments

• Multi channel analysis (ICA, PCA, etc.)
• Mechanomyography (MGM)
• Oxygen saturation measurements

TMSi System (64-128 channels for high density EMG)
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Traineeship / graduation publications

• C. Rabotti, M. Mischi, M. Gamba, M. Vinken, G.S.
  Oei, and J.W.M. Bergmans, Identification of the
  electrohysterographic volume conductor by
  high-density electrodes, 4th European Congress
  for Medical and Biomedical Engineering, Antwerp,
  Belgium, Nov. 23-27, 2008, pp. 235-238.
• J.J.F.A.H. Grootens, M. Mischi, M.Böhmer, H.H.M.
  Korsten, R.M. Aarts, Modeling of ultrasound
  propagation through contrast agents, 4th
  European Congress for Medical and Biomedical
  Engineering, Antwerp, Belgium, Nov. 23-27, 2008,
  pp. 440-443.
• M. Mischi and I. Kaashoek, Electromyographic
  hyperactivation of skeletal muscles by
  time-modulated mechanical stimulation, IEEE-EMBS
  Proc. on the 29th Annual International
  Conference, Lyon, Aug. 23-26, 2007, pp.
  5373-5376.
• B. Hermens, M. Mischi, M. Böhmer, R.M. Aarts,
  H.H.M. Korsten, Nonlinear propagation of
  ultrasound through varying contrast-agent concentr
  ations, 2nd IEEE/EMBS Benelux Symposium, Heeze,
  Dec. 6-7, 2007, pp. 42-45.
• C. Rabotti, M. Mischi, J.O.E.H. van Laar, P.
  Aelen, S.G. Oei, and J.W.M. Bergmans,
  Relationship between electrohysterogram and
  internal uterine pressure a preliminary study,
  IEEE-EMBS Proc. on the 28th Annual International
  Conference, New York, Aug. 30 - Sep. 3, 2006, pp.
  1661-1664.
• P. Aelen, C. Rabotti, M. Mischi, B. de Vries,
  J.O.E.H. van Laar, S.G. Oei, and J.W.M. Bergmans,
  Electrohysterographic estimation of intra
  uterine pressure, IEEE SPS DARTS Symposium,
  Antwerp, Mar. 28-29, 2006.
• E.C.A. van Drunen and M. Mischi, Novel device
  for dynamic force modulation in muscular
  training, 1st IEEE/EMBS Benelux Symposium,
  Brussels, Dec. 7-8, 2006, pp. 271-274.
• M. Sieben, M. Mischi, H.C.M. van den Bosch, and
  H.H.M. Korsten, Fully automated left ventricle
  segmentation method for local synchronicity
  quantification, IEEE SPS DARTS Symposium,
  Antwerp, Mar. 28-29, 2006.
• M. Mischi, A.H.M. Jansen, R.P.J. de Waard, H.H.M.
  Korsten, Contrast Ultrasound Methods for
  Left-Ventricle Ejection Fraction Measurements,
  IEEE-EMBS Proc. on the 27th Annual International
  Conference, Shanghai, Sep.1-4., 2005, pp.
  4306-4309.

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• More information

http//www.sps.ele.tue.nl