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BME 595 - Medical Imaging Applications Part 2: INTRODUCTION TO MRI Lecture 2 Basics of Magnetic...
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Transcript of BME 595 - Medical Imaging Applications Part 2: INTRODUCTION TO MRI Lecture 2 Basics of Magnetic...
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BME 595 - Medical Imaging ApplicationsPart 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 RadiologyResearch II building, E002C
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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 slideshttp://porkpie.loni.ucla.edu/BMD_HTML/SharedCode/MiscShared.html
Douglas Noll’s Primer on MRI and Functional MRIhttp://www.bme.umich.edu/~dnoll/primer2.pdf
Joseph Hornak’s Web Tutorial, The Basics of MRIhttp://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.
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Fourier Transform
Discrete case
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Fourier Transform Pairs
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Convolution Theorem
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Signal Detection:Real & Image Components
X channel (0 phase - Real)
Y channel (90 phase - Imaginary)
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Single-Channel Detection
X channel (0 phase - Real) Y channel (90 phase - Imaginary)
Problem: positive & negative frequencies cannot be distinguished!
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Quadrature Detection
+ and - frequencies can be distinguished. The entire bandwidth can be utilized
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Signal ADC With sufficient sampling rate
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Signal ADC Insufficient sampling rate causes aliasing
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K-Space EncodingUsing an Applied Gradient
Where ρ is the spin density and k is the spatial frequency
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Frequency-Encoding2-Spin Example
Dirac Delta function (line with width=0)
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Phase-Encoding
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2D K-Space -> Image Space
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Slice Selection
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Slice Selection
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Slice Selection
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Slice Selection
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Oblique Slice Selection
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Spin-Echo Pulse Sequence
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