Xray: shows bone/skull only. Does not show the brain. Best used to detect if there are bone fractures.
CT: quick test. Shows brain but detail not great. Shows if any larger bleed, stroke, lesions, or masses.
MRI: long test. Shows brain and detail is great. Shows smaller bleeds, stroke, lesions, or masses.
MRA: shows the flow of blood in the vasculature system of the brain. If there is vessel narrowing or blockage this test would show it.
PET scan: shows how active different parts of the brain is. An active brain uses sugar as energy and pet scan detects how much sugar is being used by lighting up and turning different colors. The more sugar being used the more that area will light up and be different in colors. Cancer cells use the most sugar so cancer cells light up the most. PET scan is used to see if there are cancer cells. (Cancer cells replicate at a very fast and uncontrolled rate hence use a lot of sugar to allow that replication hence why they light up so much).
Via Meddy Bear