Optimizing Contrast-Enhanced Magnetic Resonance Neurography of the Brachial Plexus With Delayed Scanning

Background

Contrast-enhanced magnetic resonance neurography (ceMRN) can enhance brachial plexus visualization and quality of imaging. However, the interval between contrast injection and scanning that provides the highest-quality images is not known.

Methods

Fifteen patients underwent brachial plexus imaging using the 3D T2-NerveView sequence with a scanning duration of 5 min. A consecutive six-phase scan was initiated immediately at the start of contrast agent injection. Subsequently, all patients' images were classified into six groups according to the phases: group A (phase 1, delay 0 min), group B (phase 2, delay 5 min), group C (phase 3, delay 10 min), group D (phase 4, delay 15 min), group E (phase 5, delay 20 min), and group F (phase 6, delay 25 min). The image quality in each group was assessed based on nerve signal (signal_nerve), muscle signal (signal_muscle), lymph node signal (signal_{lymph node}), background noise (BN), signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), and subjective score.

Results

Signal_nerve, signal_muscle, BN, and SNR did not significantly differ among the six groups (p > 0.05). However, significant differences (p < 0.05) were observed in signal_{lymph node} (F = 16.067), CNR (F = 9.495), and subjective score (χ² = 23.586). As the scanning delay increased, signal_{lymph node} intensity gradually increased whereas the CNR gradually decreased. The subjective score was significantly higher in groups B (4.83 ± 0.24), C (4.90 ± 0.21), D (4.87 ± 0.30), E (4.83 ± 0.31), and F (4.83 ± 0.31) than in group A (4.47 ± 0.30).

Conclusion

We recommend performing brachial plexus ceMRN 5 min after contrast injection. With this delay, the brachial plexus can be visualized optimally with minimal interference from background signals.