1. 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 jadchris@iupui.edu 317-274-3815

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

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

9. Signal ADC With sufficient sampling rate

10. Signal ADC Insufficient sampling rate causes aliasing

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

12. Frequency-Encoding 2-Spin Example Dirac Delta function (line with width=0)

13. Phase-Encoding

14. 2D K-Space -> Image Space

15. Slice Selection

19. Oblique Slice Selection

20. Spin-Echo Pulse Sequence

21. Homework