Inside the MRI scanner there is a powerful magnetic field
The magnetic field interacts with protons in the body
The scanner produces radiofrequency pulses which further interact with protons in the body
Protons give off 'signal' which is detected by the scanner
Once an MRI scanner is built, it remains switched on day and night, and produces a powerful magnetic field within the bore of the magnet. When the patient enters the magnet, all the protons (hydrogen ions) within their body become aligned with the magnetic field.
The scanner produces radiofrequency pulses which further interact with protons causing them to give off ‘signal’. This signal is detected by the scanner and transformed into images.
