Factors affecting the appearance  

The images above are the same axial section of the upper abdomen. The image on the left is T2 weighted and the image on the right is T1 weighted. Note the fluid filled gallbladder and the cerebrospinal fluid look quite different on the two types of images. Also note that the soft tissues, such as the liver, appear slightly different shades of gray on the two sequences.

Blood vessels, such as the aorta (labeled above) are even more complex. Not only do the machine parameters affect their appearance, but the speed and direction in which the blood flows also impacts the final image.