Sequence-dependent differences in cervical nerve root visualization on magnetic resonance imaging in dogs

Cervical nerve roots transmit motor and sensory information and are often affected by neurologic disorders. However, their small size and proximity to surrounding tissues make clear visualization on magnetic resonance imaging (MRI) challenging. In this prospective study, three MRI protocols were compared for visualizing cervical nerve roots in clinically normal dogs. Cervical MRI was performed in five healthy Beagle dogs using three sequences: turbo spin echo with Dixon (TSE+Dixon), dual-echo steady-state with water excitation (DESS+WE), and T2-weighted sampling perfection with application-optimized contrasts using different flip angle evolutions with short tau inversion recovery (T2W-SPACE+STIR). Cervical nerve root visualization was assessed qualitatively using a four-point scoring system and quantitatively using contrast-to-noise ratio (CNR). Both qualitative and quantitative analyses demonstrated sequence-dependent differences in cervical nerve root visualization. DESS+WE yielded the highest nerve root-vessel wall contrast-to-noise ratio and the highest qualitative scores for nerve root visibility and contrast at the nerve root origin in the dorsal plane, as well as for nerve root-vessel wall contrast in both planes. In contrast, TSE+Dixon yielded higher transverse-plane scores for nerve root visibility and contrast at the nerve root origin. Interobserver agreement for qualitative assessment was good across all sequences. These findings suggest that DESS+WE may be particularly useful for dorsal-plane assessment and differentiation of cervical nerve roots from adjacent vessel walls. Sequence selection should be tailored to the imaging plane and diagnostic objective rather than assuming uniform superiority of a single sequence.