Magnetic Resonance Imaging of the Peripheral Nerves and Fascicles of the Knee Using Double Echo Steady State Sequence at 7 Tesla.

Objective: To evaluate the applicability of the double echo steady state (DESS) sequence at 7 tesla (7T) for high-resolution imaging of the peripheral nerves and fascicles of the knee.

Methods: We prospectively included 32 healthy participants (mean age 39 ± 14 years, 20 females). The patients underwent 7T magnetic resonance imaging (MRI) of the knee using proton density turbo spin-echo fat suppression (PD-TSE FS), three-dimensional DESS (3D-DESS), and higher in-plane resolution DESS (DESSHR) sequences. The signal-to-noise ratios (SNRs) of the peroneal nerve (PN) and tibial nerve (TN) and contrast-to-noise ratios (CNRs) between the nerves and adjacent fat, vessels, and muscles were quantitatively measured by two readers and averaged. Five radiologists qualitatively assessed the overall image quality, pulsatile flow artifacts, and visualization of the PN and its branches, the TN, and the saphenous nerve (SN) using a five-point Likert-type scale, with the results averaged. The results of the three image sequences were compared.

Results: The SNR for the TNs in the DESSHR sequence were lower than those in the PD-TSE FS (P < 0.001) and 3D-DESS (P = 0.024) sequences, whereas the SNR for the PNs did not differ significantly across the three sequences. The DESSHR sequence exhibited superior TN- or PN-to-fat and PN-to-muscle CNR values when compared with the PD-TSE FS and 3D-DESS sequences (P ≤ 0.016). The TN- and PN-to-vessel CNR values in the DESSHR and PD-TSE FS sequences were higher than those in the 3D-DESS sequence (P ≤ 0.001). Qualitative assessments revealed fewer pulsatile artifacts in 3D-DESS than in DESSHR and PD-TSE FS (P < 0.001), with DESSHR exhibiting fewer artifacts than PD-TSE FS (P = 0.035). DESSHR excelled in visualizing the common PN, TN, and SN when compared with other sequences (P < 0.001), whereas 3D-DESS provided superior visualization of PN branches when compared with other sequences (P ≤ 0.042).

Conclusions: The DESS sequence at 7T MRI enhances visualization of peripheral nerves and fascicular structures around the knee.