MRI (Magnetic Resonance Imaging) is a revolutionary imaging technique that was first discovered by Bloch in 1945 and later improved by Lauterbur, with Mansfield, in the 1970s. The type of radiation used in magnetic resonance imaging is radio frequency (RF), which is non-ionizing. The frequency, energy and wavelength of the radiation are 10 to 100 MHz, 10-7 eV and 30 to 3m respectively. It has a high resolution in the range of mm and can be used to image the whole body.

The reason why you might need an MRI is because MRI is used extensively in clinical applications such as detecting brain disease and spinal disorders. Also, it can be used to monitor heart (cardiac) and liver function. MRI is utilized in tracking any changes in the reticuloendothelial system and musculoskeletal damage as well. If you are suspected to have any problems in these areas and the physician recommends an MRI scan, it is best you should go for one.

Another fact which calls for you to have an MRI is the emergence of functional magnetic resonance imaging, which has gained popularity in recent years. By acquiring one image of the brain in a resting state, followed by another with the brain stimulated in some way, one can compare the two images. Any regions which are different correspond to areas of brain activation. Magnetic resonance imaging can also be used to visualise patterns of blood vessels

The basic imaging principle is described as follow. Protons in water and fat inside the human body act as magnetic dipoles (small magnets). These magnets get oriented along an applied magnetic field, causing a net longitudinal magnetization. RF pulse can influence magnetisation in the transverse direction. After the RF pulse ceases, the proton spins relax back to their equilibrium situation via two relaxation processes, namely the T1 and T2 decay.

Despite the fact that magnetic resonance delivers excellent soft-tissue contrast, sometimes there is a need to administer exogenous contrast usually an intravenous injection of some paramagnetic agent. The effect of this agent is to shorten the relaxation time of local spins causing a decrease in signal on T2-weighted images and an increase on T1-weighted images

Brain images both before and after contrast enhancement allow disruptions in the blood-brain barrier to be investigated. The increased vascularity of tumours produces a preferential uptake of contrast agent and the technique can be used to better visualise these from surrounding

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