Question

How does magnetic resonance image (MRI) allow us to see details in soft nonmagnetic tissue? Use/connect magnetic field related concepts learned in class.

Answer 1

• Human body is made up of huge amount of water molecules. These water molecules consist of Hydrogen and Oxygen atoms.
• At the center of each Hydrogen atom there is a small particle called proton. These protons are very sensitive to magnetic field.
• In MRI scanning machine, human body will be subjected to magnetic field (B).
• When the magnetic field is applied, the protons in the body which are randomly arranged will align with direction of magnetic field.
• A Radio Frequency (RF) pulse is now applied in the direction perpendicular to the direction of magnetic field. Due to this RF pulse the protons will tilt away from magnetic field.
• When the RF is turned off, the protons will realign in the direction of magnetic field. This return to the equilibrium will produce radio signals and are collected by the field coils placed around the body.
• Protons in different types of tissues will realign at different speed and it will produce distinct signals. so these signals will help to differentiate between different types of nonmagnetic tissue present in the body. Also they provide information about location of protons exactly.