MRI image appearance
The easiest way to identify proton density (PD) fat saturated images is to look for adipose tissues in the body (e.g. subcutaneous fat and fat in bone marrow). Areas contain adipose tissues appear as dark on PD fat saturated images. All other characteristics of the PD fat saturated images remain same as the PD image.
Tissues and their PD fat saturated images appearance
Bone marrow: - dark
Fat – dark
Fluids – bright
White matter - darker than bright gray
Gray matter - bright gray
Moving blood- dark
Bone - dark
Air - dark
Pathologies with adipose tissues content will appear as dark in PD fat saturated images (e.g. lipoma). Due to the added fat suppression, pathological processes are usually bright on PD fat saturated images.
Very useful for extremity imaging (e.g. ankle, knee, elbow shoulder and hips)
Can be useful in thighs, lower legs, upper arms and forearms imaging
PD fat sat axial sequence used knee imaging
PD fat sat coronal sequence used ankle imaging