DESS /FADE MRI
The three-dimensional double-echo steady-state (3D-DESS) sequence employs a 3D gradient echo technique, enabling the simultaneous acquisition of two distinct steady-state free precession (SSFP) echoes with entirely different contrasts (FISP sequence and PSIF sequence). These echoes are then combined through a sum of squares calculation. The PSIF segment of the sequence imparts high T2 contrast, while the FISP portion yields representative morphological images dominated by the T1/T2 ratio. This amalgamated data yields a T2*-weighted image, enhancing sensitivity and specificity in cartilage and synovial fluid imaging.
MRI image appearance in DESS MRI
The easiest way to identify DESS images is to search for fluid-filled spaces within the body, such as cerebrospinal fluid in brain ventricles and the spinal canal, synovial fluid in joints, or any other pathological fluid collections. Fluids typically appear bright in DESS images, while muscles and fat usually appear gray. In the case of fat-saturated DESS, muscles and fat may appear dark.
Tissues and their DESS appearance
Bone marrow – dark
Muscles – bright gray
Fat – gray (darker than muscle)
Moving blood– bright
Spinal cord – gray
Cartilage – bright
Fluids – bright
Bone – dark
Air – dark
Tissues and their fat saturated DESS appearance
Bone marrow – dark
Muscles – dark gray
Fat – dark gray (darker than muscle)
Moving blood– bright
Spinal cord – gray
Cartilage – bright
Fluids – bright
Bone – dark
Air – dark
Use
- Very useful for joints imaging (fat saturated DESS in knee, hips, ankle, shoulder, wrist and elbow)
DESS sagittal image of Knee
DESS coronal image of Shoulder
