This MRI scan shows the upper torso

in side view so that the bones

of the spine are evident.

The contrast or dye materials used in X-ray and CT scan work in the same way because both areas use X-rays (ionizing radiation). These agents work by blocking the X-ray photons from passing through the area where they are located and reaching the X-ray film. This results in differing levels of density on the X-ray/CT film. These dyes have no direct physiologic impact on the tissue in the body. The contrast used in MRI is fundamentally different.

MRI contrast works by altering the local magnetic field in the tissue being examined. Normal and abnormal tissue will respond differently to this slight alteration, giving us differing signals. These varied signals are transferred to the images, allowing us to visualize many different types of tissue abnormalities and disease processes better than we could without the contrast.

Now that you know how MRI works, let's find out what circumstances might call for an MRI scan.