As soon as computed tomography or computed tomography became accessible in the 1970s, they reformed the practice of neurology. They did the scans by transmitting X-ray currents along the head at different positions and accumulating the X-ray currents on the other side that were not absorbed by the head. A sequence of images appears on a computer monitor or X-ray film as if the head had been sliced from side to side by a huge salami cutter and the slices were arranged horizontally and in series.
After that, in the 1980s, MRIs or MRIs came on the scene and astonished medical society not only by taking a picture of the brain itself, but by doing it in a new way. MRIs focus on water molecules as an alternative to imaging the degree to which different parts of the head absorb X-rays. To be more specific, MRIs represent the speed at which atoms Rotating hydrogen water molecules within various parts of the brain align or become disorganized with a powerful magnetic field. These different demagnetization or magnetization values are entered into a pc. The sliced images are formed in a sequence and displayed on a computer screen or x-ray film in shades of gray. Irregular compositions, such as brain tumors or signs of multiple sclerosis, show up in their own shades of gray and are also identifiable by their outlines and positions. More on this at http://www.medicalimagingdevices.info. Getting a different set of images after a hypodermic injection of gadolinium, which is the MRI equivalent of X-ray dye, also adds to the analytical information.
For a patient, the incident of having a CT scan and an MRI is very similar to each other. In both situations, the patient lies on an airplane table that goes in and out of a hole in the scanner that looks a lot like a large donut hole. On the MRI machine, the donut hole is narrower, so patients suffering from claustrophobia should notify their doctors if this could be a problem. Noise is also a problem with the MRI machine. A loud noise is produced each time the radio frequency coils are turned on and off. For either of these two scans, the technician may need to inject a needle into the patient’s vein to dispense a different substance.
One situation where MRIs are basically not done is when the patient has a cardiac pacemaker. This is why the magnet in the MRI machine could disturb the pacemaker and stop the heart. No image is so essential and important that this peril is worth taking. Another situation in which an MRI is avoided is when the patient is seriously ill. A serious patient can be effectively examined and held while a CT scan is being performed, but not while an MRI is being performed.