MRI Physics for Physicians

1 Overview.- 2 Magnetic Field.- Fields.- Basic Types of Magnets.- Permanent Magnet.- Superconducting Magnet.- Vectors.- Paramagentic, Diamagentic, Ferromagnetic.- Angular Momentum-Nuclear Spin.- Magnetic Dipole Moment.- Resultant BO Vector.- Precession and the Larmor Equation.- 3 Radiofrequency Pulse.- Electromagnetic Waves.- Periodic Functions.- Axis Conventions.- Perturbance of the B0 Vector.- Rotating Frame of Reference.- Resonance.- B0 vs. the Component MDM Vectors.- The Signal and the B1 Vector.- Controlling the Flip of B0.- Motion of B0 in the X-Y Plane.- 4 Relaxation.- T1 and T2 Components of Relaxation.- T1 Curves.- 5 Pulse Cycles, Pulse Sequences, and Tissue Contrast.- TR and TE.- T1 and T2 Weighting.- Balanced (Spin Density) Scans.- 6 T2 and the Spin-Echo Pulse Cycle.- Graph of MR Signal-Free Induction Decay (FID).- Envelopes of the Signal.- T2*.- Concept of Phase.- Phase and the MR Signal.- De-Phasing and the MR Signal.- Re-Phasing the MR Signal-180° Refocusing Pulse.- The Spin Echo Pulse Cycle.- The True T2 Curve.- T2 Curves for Different Tissues for Long TR'S.- T1 and T2 Constants.- T2 Curves for Different Tissues for Short TR's.- 7 Some Other Pulse Cycles.- Saturation Recovery and Partial Saturation.- Inversion Recovery.- Fast Scans.- Pulse Cycle Summary.- 8 Gradients.- 9 The Slice Select Gradient.- Changing Slice Thickness.- 10 Frequency Gradient.- The Pixel Grid.- Sine Functions for Each Pixel.- Application of Frequency Gradient.- 11 The Fourier Transform.- The Spectrum.- The Fourier Series.- Fourier Transform of Pixel Grid.- Rotating Gradients-One Alternative.- 12 The Phase Encoding Gradient.- Degrees of Phase Shift per Row.- Phase Shift in Sine Functions.- Multiple Repetitions to Form the Image.- Phase Encoding Repetitions and the Pixel Grid.-Phase Encoding Repetitions and the MDM Vectors.- The 2-D Fourier Transform.- 13 Miscellaneous Topics.- The Gradients in Perspective.- Imaging in Other Planes.- The Multislice Technique.- Averages, Excitations.- Exam Time.- 14 Coils.- Receiver, Transmitter Coils.- Gradient Coils.- Shim Coils.- Conclusion.- Appendix: The Mathematics of MRI.