Description
Springer Clinical MR Imaging and Physics A Tutorial 1st Editon 2008 Softbound by Haris S. Chrysikopoulos
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. Resonance.- Electromagnetic Fields.- Macroscopic Magnetization.- Macroscopic Magnetization Revisited.- Excitation Phenomena.- T1 Relaxation (Longitudinal or Spin-Lattice Relaxation).- T2 Relaxation (Transverse or Spin–Spin Relaxation).- Magnetic Substrates of T1 Relaxation.- Magnetic Substrates of T2 Relaxation.- Proton (Spin) Density Contrast.- Partial Saturation.- Free Induction Decay.- Spin Echo.- Integration of T1, T2, and Proton Density Phenomena.- Inversion Recovery.- Image Formation – Fourier Transform – Gradients.- Gradient Echo Imaging.- Pulse Sequences.- Fast or Turbo Spin Echo Imaging.- Selective Fat Suppression.- Chemical Shift Imaging.- Magnetization Transfer Contrast.- Diffusion.- Artifacts.- Noise.- Imaging Time.- Resolution.- Contrast Agents.- Blood Flow.- MR Angiography.- Basics of MR Examinations and Interpretation.