Subtraction of unidirectionally encoded images for suppression of heavily isotropic objects (SUSHI) for selective visualization of peripheral nerves.

INTRODUCTION

The aim of this study was to introduce and assess a new magnetic resonance (MR) technique for selective peripheral nerve imaging, called "subtraction of unidirectionally encoded images for suppression of heavily isotropic objects" (SUSHI).

METHODS

Six volunteers underwent diffusion-weighted MR neurography (DW-MRN) of the brachial plexus, and seven volunteers underwent DW-MRN of the sciatic, common peroneal, and tibial nerves at the level of the knee, at 1.5 T. DW-MRN images with SUSHI (DW-MRN(SUSHI)) and conventional DW-MRN images (DW-MRN(AP)) were displayed using a coronal maximum intensity projection and evaluated by two independent observers regarding signal suppression of lymph nodes, bone marrow, veins, and articular fluids and regarding signal intensity of nerves and ganglia, using five-point grading scales. Scores of DW-MRN(SUSHI) were compared to those of DW-MRN(AP) using Wilcoxon tests.

RESULTS

Suppression of lymph nodes around the brachial plexus and suppression of articular fluids at the level of the knee at DW-MRN(SUSHI) was significantly better than that at DW-MRN(AP) (P < 0.05). However, overall signal intensity of brachial plexus nerves and ganglia at DW-MRN(SUSHI) was significantly lower than that at DW-MRN(AP) (P < 0.05). On the other hand, signal intensity of the sciatic, common peroneal, and tibial nerves at the level of the knee at DW-MRN(SUSHI) was judged as significantly better than that at DW-MRN(AP) (P < 0.05).

CONCLUSION

The SUSHI technique allows more selective visualization of the sciatic, common peroneal, and tibial nerves at the level of the knee but is less useful for brachial plexus imaging because signal intensity of the brachial plexus nerves and ganglia can considerably be decreased.