Improved Neural Imaging Sequence and Comparison with Conventional Methods

The purpose of this study was to improve the contrast between the nerves and blood by reconsidering the imaging parameters of the sampling perfection with application-optimized contrasts using different flip angle evolutions (SPACE) method, and to compare it with conventional methods, including the constructive interference in steady state (CISS) and T2-weighted SPACE (T2-SPACE) methods. In the phantom study, the repetition time (TR), echo time (TE), flip angle (FA), and turbo factor (TF) of SPACE were varied using the restore pulse. The parameters for which the nerve-blood contrast (C1) and cerebrospinal fluid-nerve contrast (C2) were equal were selected. Though multiple conditions resulted in C1 and C2 equivalence, we determined/set the TR=500 ms, TE=21 ms, FA=120°, and TF=30, considering the acquisition time, specific absorption rate (SAR), and artifacts. This sequence was called “short TR and short TE SPACE with restore pulse (SSSR)”. In the phantom and healthy volunteer studies, the contrast between the nerves and blood in the SSSR method was statistically superior in both the physical and visual assessments compared with conventional methods. In the healthy volunteer study, C1 improved from 0.08 for CISS and 0.18 for T2-SPACE to 0.43 for SSSR. This is because the nerve signals in conventional methods were low due to the heavy T2-weighted, while those in the SSSR method were high due to the short TE and effect of the restore pulse. In conclusion, the contrast between the nerves and blood was significantly higher in the SSSR method compared with conventional methods.