Clinical MR Imaging and Physics

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.

Résumé
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. 30. 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.

Contenu
Resonance.- Electromagnetic Fields.- Macroscopic Magnetization.- Macroscopic Magnetization Revisited.- Excitation Phenomena.- T1 Relaxation (Longitudinal or Spin-Lattice Relaxation).- T2 Relaxation (Transverse or SpinSpin 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.