MRI stands for Magnetic Resonance Imaging, a diagnostic scan using strong magnetic field and radio frequency waves to get remarkably clear and detailed pictures of internal body organs and tissue.The human body consists mainly of water, and water contains hydrogen atoms. Tissues that have the least hydrogen atoms (such as bones) come out dark, and those with a lot of hydrogen atoms look much brighter, according to Dr. Sarah Burnett and Dr. John Pillinger of NetDoctor.co.uk.
