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Functional Brain Signal Processing: EEG & fMRI Lesson 10

This lecture introduces the concepts of functional brain signal processing using EEG and fMRI techniques. It covers topics such as spatial frequency, magnetic gradient, frequency encoding, and phase encoding. The trade-off challenge in MR imaging is also discussed, along with the Talairach coordinate system.

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Functional Brain Signal Processing: EEG & fMRI Lesson 10

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  1. M.Tech. (CS), Semester III, Course B50 Functional Brain Signal Processing: EEG & fMRILesson 10 Kaushik Majumdar Indian Statistical Institute Bangalore Center kmajumdar@isibang.ac.in

  2. Mezrich, 1995 K Space Localization in terms of spatial frequency . Wave number K space is named after the wave number k. K space in MR imaging http://www.psy.vanderbilt.edu/courses/hon185/SpatialFrequency/SpatialFrequency.html

  3. 3D Magnetic Gradient B(z) = B0 + G.z Z B(x) = B0 + G.x B(y) = B0 - G.y Y B(y) = B0 + G.y B(x) = B0 - G.x X B(z) = B0 - G.z

  4. Slice Location: Location Along Z axis For Hydrogen gyromagnetic ratio is 42.6 MHz/T. For a 2.5 T gradient magnetic field strength (say in a 3 T scanner) the RF pulse should be in a band 106.5 ± δ MHz. Kandel et al., 2000 Pooley, 2005

  5. Buxton, 2009 Frequency Encoding: Location Along X Axis

  6. Buxton, 2009 Phase Encoding: Location Along Y Axis

  7. Buxton, 2009 Magnetic Pulses Along X, Y and Z Axes

  8. Mezrich, 1995 MR Signal Representation in K Space ƒ(x) is the variable magnetic field

  9. Trade Off Challenge in MR Imaging Simultaneous achieving of • high spatial resolution, • high temporal resolution, and • high SNR.

  10. http://www.talairach.org Talairach Coordinate System

  11. www.brainvoyager.com Talairach Coordinate (cont.) Talairach origin is at the intersection of posterior and superior margins of the anterior commissure (AC) on the midhemispheric plane.

  12. Lancaster et al., 2007 Cerebral Dimension of Brain Templates

  13. References • R. Mezrich, A perspective on K space, RSNA, 195: 297 – 315, 1995, available online at http://pages.stat.wisc.edu/~mchung/teaching/MIA/reading/fourier.kspace.mezrich.1995.pdf • R. B. Buxton, Introduction to Functional Magnetic Resonance Imaging, 2e, Cambridge University Press, Cambridge, UK, 2009.

  14. References (cont.) • http://www.talairach.org • J. L. Lancaster et al., Bias between MNI and Talairach coordinates analyzed using ICBM-152 brain template, Hum. Brain Mapp., 28: 1194 – 1205, 2007.

  15. THANK YOUThis lecture is available at http://www.isibang.ac.in/~kaushik

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