T1 Fat Suppressed MRI Sequence
Fat saturation is an MRI technique used to suppress the signal from normal adipose tissue to reduce chemical shift artefact, improve visualization of uptake of contrast material and tissue characterization. To suppress the fat signal from an MRI sequence, a special fat suppression module is inserted at the beginning of a normal MRI sequence. Fat suppression in an MRI sequence can be achieved with five techniques: spectral fat saturation, short tau inversion recovery (STIR), spectral presaturation with inversion recovery (SPAIR), dixon method and water excitation method.
MRI image appearance of T1 fat suppressed MRI
The easiest way to identify T1 weighted 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 dark on T1 weighted fat saturated images. All the other characteristics of the T1 weighted fat saturated images remain the same as the T1 weighted images. Here’s how different tissues appear on T1 fat-saturated MRI:
- Fat Tissue: Fat appears dark on T1 fat-saturated MRI due to the suppression of its signal.
- Muscle Tissue: Muscles typically appear with intermediate signal intensity(gray) on T1 fat-saturated MRI.
- Liver: The normal liver tissue appears intermediate in signal intensity, similar to muscle.
- Kidney: Normal kidney tissue typically appears as intermediate in signal intensity on T1-fat saturated images.
- Pancreas: The pancreas can have variable signal intensity, but it’s generally intermediate.
- Spleen: The spleen typically has a signal intensity similar to the liver or muscle, being intermediate on T1-fat saturated images.
- Cerebrospinal Fluid (CSF) and Synovial Fluid: CSF and synovial fluid both appear dark (hypointense) on T1 fat-saturated MRI.
- Urinary Bladder: The urinary bladder, when filled with urine, may appear with intermediate signal intensity. The appearance can vary depending on the amount of fluid present.
- Bile Duct: The common bile duct is usually not well visualized on T1 fat-saturated MRI because it contains a mixture of fluids, bile, and surrounding tissues. It may appear as a low-intensity structure in the right context.
- Bone: Bone appears dark on T1 fat-saturated MRI.
- Pathologies containing fat: Pathologies containing adipose tissue will appear dark on T1-weighted fat-saturated images (e.g., lipoma).
Tissues and their T1 fat saturated appearance
Bone marrow : – Dark
Muscles: – Gray
Moving blood : – Dark
White matter : – Light gray
Gray matter : – Gray
Fluids : – Dark or dark gray
CSF : – Dark
Bone : – Dark
Fat : – Dark
Air : – Dark