Three-dimensional double-echo steady-state (3D-DESS) magnetic resonance imaging of the knee: contrast optimization by adjusting flip angle.

ABSTRACT

BACKGROUND: The three-dimensional double-echo steady-state (3D-DESS) sequence is being used to investigate sequence parameters for the assessment of knee cartilage by magnetic resonance imaging (MRI). With the flip angle (FA) values that are commonly used, contrast between cartilage and synovial fluid may be too low to delineate minor lesions of the cartilage surface. PURPOSE: To investigate the value of FA maximizing contrast between cartilage and synovial fluid using the 3D-DESS sequence. MATERIAL AND METHODS: In 10 healthy volunteers (five men, five women; age range 23-48 years), 3D-DESS imaging was performed to capture median sagittal sections of the knee by adjusting FA from 10 degrees to 90 degrees. Cartilage-synovial fluid contrast-to-noise ratio (CNR) was measured to determine the value of FA maximizing CNR. Water-excitation pulse was used to suppress fat signals. MRI was performed at 1.0 T using a circular polarization flex coil. RESULTS: Cartilage-synovial fluid CNR was highest with 90 degrees FA, yielding images with good contrast between cartilage and synovial fluid. CONCLUSION: Simply by increasing FA to 90 degrees in 3D-DESS imaging, the contrast between cartilage and synovial fluid increased substantially. Subtle cartilage lesions may thus be detectable using 3D-DESS sequences.