MRI Scanning Lecture Notes (PDF)

Lecture One Assistant.L.Huda Sahi Third Stage ‫ـــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ ــــــــــــــــ...

Lecture One Assistant.L.Huda Sahi Third Stage ‫ـــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ ـــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬ If a radiofrequency (RF) pulse having a frequency equal to the Larmor frequency of tissue is applied perpendicular to the magnetic field, then it is absorbed by the proton nuclei and changes the direction of spinning in the opposite direction to which they were previously spinning. This process is called Resonance. When the RF pulse is finally turned off, the unmatched hydrogen atoms gradually return to their original position and emit a certain kind of energy. This process is called Relaxation. This energy is then detected by the highly sensitive antenna, which feeds the data into the computer system in the form of waves or signals. Finally, the computer system interprets this data and converts the signal into a visible and understandable image that can be read and studied by the doctors and scientists. See figure 5 below: 7 ‫‪Lecture One‬‬ ‫‪Assistant.L.Huda Sahi‬‬ ‫‪Third Stage‬‬ ‫ـــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ ـــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬ ‫‪Figure 5: Steps of MRI scanning.‬‬ ‫‪8‬‬