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James D. Christensen, Ph.D. IU School of Medicine

BME 595 - Medical Imaging Applications Part 2: INTRODUCTION TO MRI Lecture 2 Basics of Magnetic Resonance Imaging Feb. 23, 2005. James D. Christensen, Ph.D. IU School of Medicine Department of Radiology Research II building, E002C jadchris@iupui.edu 317-274-3815. References.

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James D. Christensen, Ph.D. IU School of Medicine

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  1. BME 595 - Medical Imaging ApplicationsPart 2: INTRODUCTION TO MRILecture 2 Basics of Magnetic Resonance ImagingFeb. 23, 2005 James D. Christensen, Ph.D. IU School of Medicine Department of RadiologyResearch II building, E002C jadchris@iupui.edu317-274-3815

  2. References Online resources for introductory review of MRI physics: • Robert Cox’s book chapters online • http://afni.nimh.nih.gov/afni/edu/ • See “Background Information on MRI” section • Mark Cohen’s intro Basic MR Physics slides • http://porkpie.loni.ucla.edu/BMD_HTML/SharedCode/MiscShared.html • Douglas Noll’s Primer on MRI and Functional MRI • http://www.bme.umich.edu/~dnoll/primer2.pdf • Joseph Hornak’s Web Tutorial, The Basics of MRI • http://www.cis.rit.edu/htbooks/mri/mri-main.htm Books covering basics of MRI physics: • E. Mark Haacke, et al. Magnetic Resonance Imaging: Physical Principles and Sequence Design, 1999. • D. Shaw. Fourier Transform NMR Spectroscopy, 1976. • R. N. Bracewell. The Fourier Transform and its Applications, 1965.

  3. Fourier Transform Discrete case

  4. Fourier Transform Pairs

  5. Convolution Theorem

  6. Signal Detection:Real & Image Components X channel (0 phase - Real) Y channel (90 phase - Imaginary)

  7. Single-Channel Detection Problem: positive & negative frequencies cannot be distinguished! X channel (0 phase - Real) Y channel (90 phase - Imaginary)

  8. Quadrature Detection + and - frequencies can be distinguished. The entire bandwidth can be utilized

  9. Signal ADCWith sufficient sampling rate

  10. Signal ADC Insufficient sampling rate causes aliasing

  11. K-Space EncodingUsing an Applied Gradient Where ρ is the spin density and k is the spatial frequency

  12. Frequency-Encoding2-Spin Example Dirac Delta function (line with width=0)

  13. Phase-Encoding

  14. 2D K-Space -> Image Space

  15. Slice Selection

  16. Slice Selection

  17. Slice Selection

  18. Slice Selection

  19. Oblique Slice Selection

  20. Spin-Echo Pulse Sequence

  21. Homework

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