Microwave imaging technique for biomedical application


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Microwave imaging technique for biomedical application

  1. 1. Microwave Imaging Technique for Biomedical Application Gunjan Gupta Nirma University gunjan101@gmail.com
  2. 2. Introduction • The penetration through opaque media makes microwaves a convenient agent for non invasive testing, evaluating cold measurements • Microwaves have been considered for medical applications involving the detection of organ movements and changes in tissue water content • Cardiopulmonary interrogation via microwaves has resulted in various sensors for monitoring various movements and changes inside human body 2http://www.linkedin.com/in/gunjgupta
  3. 3. Introduction • In all these applications, microwave sensors perform local measurements and need to be displaced for obtaining an image reproducing the spatial variations of a given quantity • Recently advances in the area of inverse scattering theory and microwave technology have made possible the development of microwave imaging and tomographic instruments 3http://www.linkedin.com/in/gunjgupta
  4. 4. What Paper Covers ? • Equipments developed at Supelec and UPC Barcelona, within the frame of successive French-Spanish PICASSO cooperation programs • Brief historical survey for both technological and numerical aspects • Capabilities of the existing equipment, as well as difficulty in dealing with clinical situations • Expected development of microwave imaging techniques for biomedical applications 4http://www.linkedin.com/in/gunjgupta
  5. 5. Reconstruction Algorithm • Main difficulty in producing microwave images of quality was to compensate for complex diffraction mechanisms • Two Approaches: • First , Efficient reconstruction algorithms used with X-ray CT • Second, Scattering Mechanism with more rigorous nature in Reconstruction Process 5http://www.linkedin.com/in/gunjgupta
  6. 6. Reconstruction Algorithm X-Ray CT Reconstruction • Compensate the effect of Scattering Phenomenon • Neglect Multiple Scattering • Approach, imported from Ultrasound Imaging technique , is known as Diffraction Topography Scattering Reconstruction • Scattering mechanism are formally taken into account with more rigorous nature • Linearize the inverse scattering problem, scattered field are linearly related to equivalent current induced by interrogating beam 6http://www.linkedin.com/in/gunjgupta
  7. 7. Reconstruction Algorithm X-Ray CT Reconstruction • Fast Fourier Transform Algorithm • Efficient under computational aspect & suited for real time op • Does not allow quantitative imaging • Reproduce shape of structure Scattering Reconstruction • Fourier Transform Algorithm • Allow quantitative imaging, even for high contrast targets 7http://www.linkedin.com/in/gunjgupta
  8. 8. Iterative Reconstruction Algorithm 8http://www.linkedin.com/in/gunjgupta
  9. 9. Iterative Reconstruction Algorithm • At each step , the measured scattered field is compared to the scattered field calculated from a numerical model • Such an approach, equivalently known as Distorted Born Method or Newton Kantorovitch Technique (NKT) , has been developed at the end of the 80’s and has been shown to be able to deal with high contrasted structures • Spatial resolution is not so strictly related to the wavelength 9http://www.linkedin.com/in/gunjgupta
  10. 10. Equipments • Equipment differ from the geometry of the transmitter receiver arrangement • Designed for operation according to a transmission mode in water, at a frequency of the order of 2 GHz • Provides a satisfactory optimization between a desired investigation depth of about 20 cm, and a spatial resolution comprised between 5 and 10 mm 10http://www.linkedin.com/in/gunjgupta
  11. 11. Equipments Planer Microwave Camera @2.45 GHz Circular Microwave Scanner @2.33 GHz 11http://www.linkedin.com/in/gunjgupta
  12. 12. Result • Microwave camera has been initially designed for non-invasive thermometry (NIT) purposes during hyperthermia sessions • Hyperthermia is demanding for an accurate control of the temperature distribution in the heated tissues • Such a control is impossible to obtain in case of deep seated tumors, except with invasive thermometric probes 12http://www.linkedin.com/in/gunjgupta
  13. 13. Result • In all trials, the time required for reconstructing images was too long for obtaining interactivity between operator and equipment • However, very recently, the microwave camera has been made compatible with real time constraints • Images can now be produced at the rate of more than 10 images per second, which is enough for most biological processes 13http://www.linkedin.com/in/gunjgupta
  14. 14. Result Fig : Microwave image of a human hand. Mono-view reconstruction with a diffraction tomography algorithm 14http://www.linkedin.com/in/gunjgupta
  15. 15. Human for-arm reconstructed from Microwave scanner data Linear Diffraction Tomography Non-linear Iterative Technique 15http://www.linkedin.com/in/gunjgupta
  16. 16. Conclusion • From the beginning of the 80’s , microwave imaging techniques for biomedical applications have been drastically improved • Various assessments conducted with preliminary Equipments have confirmed the sensitivity of microwave images to factors of medical relevance • Even if operational and clinical efficacy is not yet achieved, different steps for succeeding are now well identified 16http://www.linkedin.com/in/gunjgupta
  17. 17. Indeed, without a significant development effort, microwave imaging techniques will still have to wait a long time before being recognized and accepted by their potential users Thank You ! 17http://www.linkedin.com/in/gunjgupta
  18. 18. Reference IEEE Paper 18http://www.linkedin.com/in/gunjgupta