Ct and MRI
are cross sectional imaging
techniques which have revolutionized the ability to make diagnoses that previously required invasive studies.
Ct scans utilize ionizing radiation, like a chest x-ray. Mri scans utilize a very powerful magnet field that causes water and other molecules to line up like a compass in a magnetic field. When the magnetic field is released, the energy released by the movement of molecules leads to distinct signals that can be analyzed and used to reconstruct an image. In both scans, contrast agents can be used to increase the ability to look at specific structures, such as blood vessels and other hollow structures.
While both scans provide internal images, each type of scan has some distinct advantage over the other. Occasionally it may be necessary to get both scans, but in general, depending on the situation, one or the other is generally used.