most abundant. The patients lie within the powerful magnet where the magnetic field of the scanner is used to align the hydrogen atoms in the body. Inserting a radio frequency pulse alter the precession (spins) alignment of this hydrogen atom thus creating a spatial resolution image. Once an image is formed the computer must perform Fourier Transformation calculation to make the image readable on the workstation for the radiologist to diagnose the patient. Magnetic fields gradients cause nuclei at different locations to rotate at different speeds and vectors to obtain 2D images or 3D volumes. Compared with other medical imaging techniques MRI provides good contrast between the different soft tissues of the body, which is especially useful in imaging the brain, muscles, the heart, and cancers. The MRI does not use ionizing radiation. HOW MRI WORKS MRI machines recognize the fact that the body tissues have lots of water therefore protons, which in a magnetic field get aligned. While a person is inside the magnetic field of the scanner, the protons become aligned and a radio frequency pulse is generated
perpendicular to the magnetic field. Basically, hydrogen atoms precess (spins) in a wobbling northward direction parallel to the magnets field. Next, a RF pulse hits the atoms or knocks its feet from underneath it which the atom falls down or is now perpendicular to the magnetic field in either an eastward or westward direction. Eventually, after the RF pulse ends the hydrogen atom returns to its original parallel state of direction. In clinical practice, MRI is used to distinguish pathological tissue from normal tissue. One advantage of the MRI is that it is harmless to the patient. It uses strong magnetic fields and non-ionizing electromagnetic field in the radio frequency range, unlike other traditional X-Rays. MRI has the ability to distinguish the differences between two arbitrarily similar but not identical tissues and the basis of this is the complex library of pulse sequences that the modern medical MRI scanner includes, each of which is suitable to provide image contrast based on the chemical sensitivity of MRI. The basic parameters of image acquisition are echo time (Te) and the repetition time (Tr), with this values a sequence takes on the property of T2-weighting (spin-spin relaxation). For example, on a T2-weighted scan, waterand fluid- containing tissues are bright and
producing a varying electromagnetic field with varying frequencies between the patients head to feet which is absorbed at a select gradient field and cause the hydrogen atoms to flip the spin of the protons in the direction