Principles of MRI:

Our body made up of chemical composition (ie: hydrogen, carbon, nitrogen sodium, phosphotus, potassium etc.)

Atoms these elements have different number of protons in their nucleus and possess different magnetic property.

Protons of hydrogen atom are the most abundant in the body in the form of water.

Magnetic properties of these atoms have been utilized to produce magnetic resonance signals and images.

When a patient is placed in a strong magnetic field in MR scanner, hydrogen nucleus in the body align with the applied external magnetic field.

Hydrogen nuclei in the patients body absorbs the energy and then generates the MR signal when exposed to short bursts of electromagnetic energy in form of radio frequency pulse.

The magnet creates a strong magnetic field which aligns the protons of hydrogen atoms which are then exposed to a beam of radio waves.

This spins the various protons of the body and produce a faint signal which is detected by receiver portion of the MRI scanner. The receiver information is processed by computer and image is produced.

Advantages :

1. Excellent soft tissue contrast resolution

2. Ability to obtain direct transverse, sagittal, coronal and oblique images

3. Does not use ionizing radiation

4. Does not produce bone/air artefacts


1. Longer imaging time

2. Complexity of the equipment and scan acquisition

3. High Cost

4. Inability to demonstrate calcification or cortical bone details

5. Bullet shrapnel and metallic fragments may move and become projectile (Contraindicated for patients with Cardiac pacemakers, dental implants, heart valve prosthesis and aneurysm clips)






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