MRI Concepts and Relaxation Mechanisms

The video tutorial explains how MRI works, starting with the influence of magnetic fields on the body. It covers the alignment of nuclei under a strong magnetic field, the concept of precession and resonance, and the Larmor equation. The process of MRI signal acquisition is divided into five phases: pre-scan, excitation, relaxation, acquisition, and computing/display. The tutorial details T1 and T2 relaxation processes, explaining how they differ and their significance in MRI imaging. Finally, it describes how signals emitted during relaxation are captured and processed to form MRI images.

What is the term used to describe the wobbling movement of nuclei in a magnetic field?

• Vibration

• Oscillation

• Rotation

• Precession

What happens to the nuclei in the body when exposed to a strong external magnetic field?

• They align randomly.

• They align parallel or anti-parallel to the field.

• They stop moving.

• They become electrically charged.

What is the purpose of the pre-scan phase in MRI?

• To align the patient's body

• To determine the processing frequency of nuclei

• To apply the magnetic field

• To capture the final image

During the excitation phase, what happens to the net magnetic vector?

• It disappears.

• It remains stationary.

• It flips into the x-y plane.

• It aligns with the z-axis.

What is T1 relaxation also known as?

• Longitudinal relaxation

• Transverse relaxation

• Spin-lattice relaxation

• Spin-spin relaxation

How is T2 relaxation different from T1 relaxation?

• It occurs along the z-axis.

• It does not emit any signal.

• It is slower than T1 relaxation.

• It involves the loss of transverse magnetization.

What percentage of transverse magnetization is lost during T2 relaxation?

• 100%

• 63%

• 50%

• 75%

What happens to the signal emitted during relaxation?

• It is absorbed by the body.

• It is lost in the environment.

• It is ignored.

• It is captured by the MRI machine's receiver coils.

What role do receiver coils play in MRI imaging?

• They generate the magnetic field.

• They apply radio frequency pulses.

• They capture emitted signals.

• They display the final image.

How is the final MRI image formed?

• By direct observation

• Using photographic techniques

• Through signal processing and display

• By manual drawing