Introduction

Assessment of cervical nerve roots is important as well as the brachial plexus MR Neurography when deciding surgical procedures in some cases, such as traumatic brachial plexus injuries and neonatal brachial plexus palsy.1,2 Since the cervical nerve roots are the complex anatomy, such small nerves cannot be visualized well by the conventional MRI.3 We have demonstrated that the combined use of SHINKEI MR neurography4 and phase-cycling balanced SSFP (and its complex subtraction images) has been useful to visualize both the brachial plexus and nerve roots within a feasible scan time.5 However, it is still challenging to clearly visualize both the brachial plexus and nerve roots in a short scan time without motion misregistration because separately acquired two imaging datasets are required, one single scan would therefore be desired. Double Echo Steady-State (DESS) with water-selective excitation is a useful sequence to depict small nerves such as intracranial nerves,6,7 it would also be promising for visualizing cervical nerve roots. DESS sequence chart is shown in table1. Furthermore, 3D quantitative DESS (qDESS) offers a rapid simultaneous 3D morphometry and T2 relaxometry.8-10 Recently, accelerated qDESS sequence combined with compressed sensing sensitivity encoding (Compressed SENSE) has been proposed for rapid 3D knee morphological and quantitative imaging11. In this study, we evaluated appropriate parameters of accelerated qDESS to improve demonstration of both the cervical nerve roots and the brachial plexus within a short scan time.

Methods

Five healthy volunteers (4 males, 1 female, age 25-45 years old) were examined by 3.0T MRI (Ingenia, Philips Healthcare). Suitable flip angle (FA) and 3D voxel size of accelerated qDESS were evaluated as follows; 1. Assessment of optimized FA FA was set to 15, 25, and 35 degrees to assess image contrast between the cervical nerves and surrounding background. The other parameters were: TR/TE1/TE2=17/5.0/12.3ms, FOV=200x200x120 mm, slice thickness=1.2 mm, slice number=200, acquisition time=2:32. 2. Assessment of optimized 3D voxel size 3D voxel size was set to 0.8mm3, 1.0mm3, 1.2mm3 (iso-voxel size) to evaluate visualization of both the nerve root and the brachial plexus. The imaging parameters were shown in Table 1. These visual evaluations were performed by three radiologists and radiological technologists using a 5-point scale: 0, non-evaluative; 4, excellent quality.

Results and Discussion

Results and Discussion FA has a very important role for generating contrast between the cervical nerve roots and surrounding tissues, such as the muscles, cerebrospinal fluid, and blood vessels. The visual evaluation scores of accelerated qDESS using FA: 35 degree was significantly higher than others (Figure 2) and the brachial plexus were most clearly demonstrated using it. Accelerated qDESS using 0.8mm3 isotropic acquisition showed the most detailed anatomy of the ventral roots (Figure 3). Figure 4 was the representative accelerated qDESS images with optimized parameters: FA: 35 degree and 0.8mm3 isotropic acquisition. It could provide detailed anatomical structures of cervical nerve roots with sufficient spatial resolution, image contrast, and signal to noise ratio. The optimized accelerated qDESS images clearly demonstrated the entire cervical nerve roots and it can provide quantitative information.

Conclusion

Accelerated qDESS clearly visualized the whole brachial plexus including small nerve roots with a quantitative information. It could be a helpful sequence to contribute to the diagnosis of nerve root and peripheral nerve disorders such as radiculopathy.

Acknowledgements

No acknowledgement found.

References

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