Clinical MR Imaging and Physics: A Tutorial

Description

Keywords Spin › Electromagnetic radiation › Resonance › Nucleus › Hydrogen › Proton › Certain atomic nuclei possess inherent magnetic Let us summarize the MRI procedure. Te patient properties called spin, and can interact with electro- is placed in a magnetic feld and becomes temporarily 1 magnetic (EM) radiation through a process called magnetized. Resonance is achieved through the - resonance. When such nuclei absorb EM energy they plication of specifc pulses of EM radiation, which is proceed to an excited, unstable confguration. Upon absorbed by the patient. Subsequently, the excess - return to equilibrium, the excess energy is released, ergy is liberated and measured. Te captured signal producing the MR signal. Tese processes are not is processed by a computer and converted to a gray random, but obey predefned rules. scale (MR) image. Te simplest nucleus is that of hydrogen (H), con- Why do we need to place the patient in a m- sisting of only one particle, a proton. Because of its net? Because the earth’s magnetic feld is too weak to abundance in humans and its strong MR signal, H be clinically useful; it varies from 0. 3–0. 7 Gauss (G). is the most useful nucleus for clinical MRI. Tus, foC r urrent clinical MR systems operate at low, mid or our purposes, MRI refers to MRI of hydrogen, and for h igh feld strength ranging from 0. 1 to 3. Front Matter....Pages I-IX Resonance....Pages 1-1 Electromagnetic Fields....Pages 2-2 Macroscopic Magnetization....Pages 3-4 Macroscopic Magnetization Revisited....Pages 5-6 Excitation Phenomena....Pages 7-8 T1 Relaxation (Longitudinal or Spin-Lattice Relaxation)....Pages 9-10 T2 Relaxation (Transverse or Spin–Spin Relaxation)....Pages 11-12 Magnetic Substrates of T1 Relaxation....Pages 13-15 Magnetic Substrates of T2 Relaxation....Pages 16-16 Proton (Spin) Density Contrast....Pages 17-17 Partial Saturation....Pages 18-18 Free Induction Decay....Pages 19-19 Spin Echo....Pages 20-21 Integration of T1, T2, and Proton Density Phenomena....Pages 22-24 Inversion Recovery....Pages 25-27 Image Formation – Fourier Transform – Gradients....Pages 28-31 Gradient Echo Imaging....Pages 32-38 Pulse Sequences....Pages 39-39 Fast or Turbo Spin Echo Imaging....Pages 40-42 Selective Fat Suppression....Pages 43-51 Chemical Shift Imaging....Pages 52-55 Magnetization Transfer Contrast....Pages 56-61 Diffusion....Pages 62-69 Artifacts....Pages 70-80 Noise....Pages 81-81 Imaging Time....Pages 82-82 Resolution....Pages 83-84 Contrast Agents....Pages 85-89 Blood Flow....Pages 90-93 MR Angiography....Pages 94-108 Basics of MR Examinations and Interpretation....Pages 109-163 Back Matter....Pages 164-176