Comparison of Three-Dimensional Double-Echo Steady-State Sequence with Routine Two-Dimensional Sequence in the Depiction of Knee Cartilage

There are some routine two-dimensional sequences, including short tau inversion recovery (STIR), T2-weighted fast-spin echo (T2W-FSE), and proton-density fast spin-echo for diagnosing osteoarthritis and lesions of the knee cartilage. However, these sequences have some disadvantages, such as long scan time, inadequate spatial resolution, and suboptimal tissue contrast which results in loss of image details, as well as missing the visualization of knee cartilage lesions. Three-dimensional (3D) sequences, such as the double-echo steady-state (DESS) sequence can decrease and overcome these problems to the smallest possible amount.

A total of 15 volunteers with knee pain were examined by a 1.5 Tesla magnetic resonance imaging.The contrast-to-noise ratio (CNR) and thickness values of the knee articular cartilage were measured. The CNR and thickness values were comparedby the Friedman test and the Wilcoxon signed-rank test.

The obtained results showed significant differences between sequences in CNR and thickness values. The DESS sequence with a flip angle of 40°showed the best CNR values and 3D fast low-angle shot (FLASH) showed the worst results. In addition, the results showed no significant differences between FLASH, 3D DESS 40° and 90° in terms of cartilage thickness. However, thickness values of these sequences were much higher than that of the PD, T2, and STIR sequences.

The 3D DESS sequence with two flip angles of 40°and 90° are the best sequences for visualizing the cartilage and the synovial fluid. Because they provide the best contrast between the cartilage and the synovial fluid, it is recommended to use DESS sequences in the evaluation of cartilage defections.