Researchers and clinicians who investigate the spinal cord by using diffusion-weighted imaging and tractography.White matter (WM) tractography and diffusion MRI (dMRI) derived quantitative metrics, such as fractional anisotropy (FA), mean diffusivity (MD) and mean kurtosis (MK) are promising tool to investigate spinal cord microstructures. Recently, diffusional kurtosis imaging (DKI) - based fiber-tracking technique was introduced for WM tractography as a solution for crossing fibers by using the kurtosis diffusion orientation distribution function^1. Therefore, this technique seemed to be more robust for WM tractography, compared with conventional diffusion tensor imaging (DTI)-based WM tractography. Moreover, multi-band echo-planar imaging (MB-EPI) technique has been introduced for diffusion-weighted imaging as a useful tool to reduce scanning time² for clinical use of multi-shell dMRI data acquisition, such as DKI. The purpose of this study is to investigate the effect of multi-band reduction factor (MBf) of MB-EPI on WM tractography and dMRI metrics and to compare DKI tractography with conventional DTI tractography in vivo.Spinal cord diffusion datasets with MBf of 2 and 3 were each collected from one healthy volunteer using a 3.0T MR system (Magnetom Skyra, Siemens AG, Erlangen, Germany) using a 20–channel head/neck receiver coil. Imaging parameters for 2-shell diffusion protocol were as follows: repetition time/echo time, 5000/102.4 (ms/ms); number of signals acquired, one; section thickness, 3 mm; 54 slices; field of view, 150 x 150 mm2; matrix, 150x 150; imaging time, approximately 9min. for MBf of 1 and 6 min for MBf of 2 and 3, respectively; 3 b values (0, 1000, and 2000 s/mm²) with diffusion encoding in 30 directions for every b value. Δ = 50.6 ms and δ = 19.2 ms for both shells. Spinal cord WM tractography from C2 to C6 level and diffusion metrics maps were obtained and analyzed with Diffusional Kurtosis Estimator(DKE)³ software version 2.6.0 (http://academicdepartments.musc.edu/cbi//dki/DKE/dke_download.htm.), DKE Fiber Tractography Module1　and the TrackVis software (www.trackvis.org). Six-parameter rigid-body co-registration between dMRI data of DKI was performed as a function of DKE software. Both DKE and DTI tractography procedures were implemented for MBf of 2 and 3 data to estimate number of fibers and DKI and DTI derived metrics: FA, MD, MD, kurtosis FA. Statistical evaluations were performed by using IBM SPSS Statistics software (version 19.0; SPSS, Chicago, IL). P value less than 0.05 was considered to indicate a statistically significant difference.The numbers of WM tracts increased in DKI tractography, compared with DTI tractography on the same condition of MBf. Moreover, the numbers of WM tracts decreased in MBf of 3 data, compared with MBf of 2 data in both tractography methods. The results for the numbers of WM tracts are shown in Table 1.There was no significant difference in all diffusion metrics between MBf of 2 and 3 data and DKI- and DTI based tractography (all P > 0.5, Mann-Whitney U test). Their values of each diffusion metric in different condition are shown in Table 2.Based on our results, DKI based method seemed to be more robust technique for WM tractography than DIT-based one, even though simple structure of WM bundles, such as spinal cord WM tracts. Moreover, MB-EPI technique is useful technique to reduce scanning time, however, dMRI data with higher number of MBf may lead to unfavorite results of WM tractography, presumably due to image quality degeneration. Unchanged diffusion metrics values were observed on any conditions. However, this is not guaranteed on pathologic condition. Limitation of this study is a single subject analysis and using no patient data. Larger population and inclusion of disease patient study and sequence optimization will be needed before clinical use.In conclusion, DKE-based method seem to be preferable instead of DTI-based one for spinal cord WM tractography. Moreover, MBf of 2 is recommended for spinal cord WM tractography with this technique.