Microwave imaging for thermal therapy

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Use microwave tomographic imaging for temperature monitoring in thermal therapy

Use microwave tomographic imaging for temperature monitoring in thermal therapy

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  • 1. Integrated Microwave Thermal Imaging System with Mechanically Steerable HIFU Therapy Device
    Tian Zhou
    01/26/09
  • 2. Outline
    Purpose
    Principles of Microwave Imaging
    Dielectric Properties vs. Temperature Change
    Integration of Microwave Thermal Imaging and HIFU Heating (Configuration I, II)
    Challenges
    2
  • 3. Purpose
    3
  • 4. Principles in Microwave Imaging
    Dielectric Properties
    Permittivity, ɛ
    a measurement of energy storage in a material from an external electric field
    Conductivity, σ (siemens/m)
    how dissipative or lossy a material is to an external electric field*
    *Agilent tech notes
    4
  • 5. Principles in Microwave Imaging
    5
  • 6. Relationship between Dielectric Properties and Temperature
    In literature
    Liver tissue
    ex vivo
    @915MHz
    @2.45GHz
    Susan C. Hagness et al.
    (2006)
    6
  • 7. Integrating MW Imaging and HIFU Heating
    Temperature change will alter the dielectric properties of a phantom or tissues
    Microwave imaging is able to capture the change of the dielectric properties
    Microwave imaging can be a potential non-invasive tool to provide feedback of the thermal profile in HIFU heating
    7
  • 8. HIFU Heating
    13 W
    8 W
    Cyril Lafon et al. (2001)
    8
  • 9. Microwave imaging system
    9
  • 10. Integrating MW Imaging and HIFU Heating
    10
  • 11. System Setup
    11
    Phantom
  • 12. Difference Image
    12
    T = tiT = t0 Difference Image
  • 13. Difference image
    Circle
    Conductivity Difference Image
    Courtesy of ShireenGeimer
    13
  • 14. Difference image
    C-circle
    14
    Conductivity Difference Image
  • 15. Difference image
    Spirals
    15
    Conductivity Difference Image
  • 16. Spatial Registration
    16
    Conductivity Difference Image
  • 17. Temporal Registration
    Temperature
    Normalized
    conductivity
    (1100MHz)
    17
  • 18. Conductivity vs. Temperature Change
    Conductivity
    Temperature (°C)
    18
  • 19. New Configuration for Integration
    Waveform
    Generator
    Power
    Amp.
    MW antenna
    Temp.
    Meter
    Stepper
    Controller
    HIFU transducer
    Thermal couples
    DMAS
    System
    Beam focus
    19
  • 20. New Configuration for Integration
    20
    Phantom
    Transducer
    heated
    plane
    focal zone scan path
    Focus
  • 21. Steerable HIFU Transducer
    21
  • 22. Cross Section of a Focal Beam
    22
    1X power level
    1.5X power level
  • 23. Cross Section of a Focal Zone
    23
    Permittivity
    Conductivity
    Permittivity
    Conductivity
  • 24. Animal Experiment
    24
  • 25. Challenges
    25
    Spatial Resolution
    Better with higher frequency, but higher attenuation
    Compromise between spatial res. and SNR
    Registered with images which have fine anatomic details
    Temporal Resolution
    Currently reconstructed offline
    Understanding the Relationship between Dielectric Properties and Temperature Change
    Nonlinear in vivo
  • 26. Acknowledgement
    Thayer School, Dartmouth College
    Paul Meaney, PH.D
    Keith Paulsen, PH.D
    Shireen Geimer
    Margaret Fanning
    Lincoln Potwin
    Tim Raynolds
    Dartmouth Hitchcock Medical Center
    P. Jack Hoopes, D.V.M., PH.D
    Susan Kane
    NIH
    26
  • 27. Phantom experiment
    Relationship between Dielectric Constant and Temperature
    27
    Temperature (C)
    Temperature (C)