Imagerie par Résonance Magnétique (IRM)

Magnetic Resonance Imaging (MRI) is a non-invasive imaging technique used to study the anatomy and physiology of the human body.

The principle of MRI relies on the unique magnetic properties of hydrogen nuclei, specifically their ability to align with an external magnetic field.

The primary benefit of MRI is its non-invasive nature. It doesn't use ionizing radiation like X-rays, making it a safer option for repeated scans.

MRI uses a strong magnetic field to align the hydrogen nuclei in the body. When radio waves are applied, these nuclei absorb energy and then release it, generating a signal that is detected by the MRI machine.

Hydrogen nuclei, also known as protons, possess a unique characteristic: they spin on their axis, creating a tiny magnetic field. In MRI, these spinning protons are aligned by a strong external magnetic field.

The process of applying radiofrequency pulses to excite the aligned hydrogen nuclei in the body is called 'excitation.'

The measurement of the transverse magnetization of various tissues in the body is a crucial step in the MRI process. This magnetization is directly linked to the water content and other characteristics of the tissue.

After the excitation, the hydrogen nuclei return to their original state, releasing the absorbed energy as a radio frequency signal. This signal is detected by the MRI machine and converted into an image.

Nuclear Magnetic Resonance (NMR) is the fundamental physical phenomenon underlying MRI. It describes the interaction of atomic nuclei with magnetic fields, leading to the absorption and release of energy.

The hydrogen nuclei are essential in MRI because they possess a high intrinsic angular momentum, making them highly sensitive to magnetic fields. This sensitivity allows for efficient signal generation, which is crucial for creating detailed anatomical images.