Contrast is the difference in brightness between different areas of the image which enables us to see things. The contrast results from differences in the physical or chemical properties of the various parts of the sample. The MRI system can be adjusted to change the contrast - sort of like changing the color of light used to illuminate an object. T2 contrast tends to enhance the brightness of liquids such as water. T1 contrast enhances fats, and sometimes more viscous substances.
Solid tissues tend to be dark in both contrast types.
Experienced users may wish to change the individual parameters as well. There are limits on the values of some parameters. These are shown in brackets next to the parameter field. Values outside this range will be ignored. Legal, but invalid, combinations may cause the MRI system to hang up.