Effect of distortion corrections on the tractography quality in spinal cord diffusion‐weighted imaging

Abstract

Purpose To assess the impact of a different distortion correction (DC) method and patient geometry (sagittal balance) on the quality of spinal cord tractography rendering according to different tractography approaches. Methods Forty‐four adults free of spinal cord diseases underwent cervical diffusion‐weighted imaging. The phase‐encoding direction was head→foot. Sequence with opposed polarities (foot→head) was acquired to perform DC. Eddy‐current, motion effects, and susceptibility artifact correction methods were used for DC, and two deterministic and one probabilistic tractography approaches were evaluated using MRtrix and DSI Studio tractography software. Fiber length and number of fibers were extracted to evaluate the quality of the tractography rendering. For each subject, cervical lordosis was measured to assess patient geometry. The angle between the main direction of the spinal cord and the orientation of the acquisition box were computed at each spine level to assess acquisition geometry and define an angle threshold for which a tractography of good quality is no longer possible. Results There was a significant improvement in tractography quality after performing DC with susceptibility artifact correction using a deterministic approach based on tensor. Before DC, the angle threshold was defined at C6 (15.2°) compared with C7 (21.9°) after corrections, demonstrating the importance of spinal cord angulation for DC. Conclusion The impact of DC on tractography quality is greatly impacted by acquisition geometry. To obtain a good‐quality tractography, we propose as a future perspective to adapt the acquisition geometry to that of the patient by automatically adjusting the acquisition box.

Geometric Evaluation of Distortion Correction Methods in Diffusion MRI of the Spinal Cord

“…Last, we note as shown in Table . Table . 4 that Voss performs significantly better in the subjective evaluation than TOPUP. However, TOPUP method is recognized as the major method for the postprocessing distortion correction of diffusion MRI data [31,32].…”

Utility of Diffusion and Magnetization Transfer MRI in Cervical Spondylotic Myelopathy: A Pilot Study

“…In healthy controls, above the lesion and below the lesion level were analyzed in C2/3 and C7/T1 as in the patient group. As there was no lesion level in the control group, the C5/6 level was selected for comparison with the lesion level of the patients [ 4 , 20 ]. Figure 1 shows the sagittal slices and axial slices of two patients at above the lesion level, the maximum compression level, and below the lesion level.…”

“…In addition, findings obtained within the cord vary based on the location, e.g., whether it is in the ascending or descending tract [ 17 , 18 ]. Successful spinal cord tractography depends on many factors, such as image acquisition settings, region of interest design, and distortion correction [ 19 , 20 ]. With the development of imaging techniques and the availability of excellent software, it is now possible to discriminate between detailed structures, such as columns within the spinal cord, which enables tract-specific analysis [ 15 , 20 , 21 , 22 ].…”

Full cervical cord tractography: A new method for clinical use

“…ROI design"), and both single and multiple ROI designs have disadvantages (user-dependent and time-consuming). When using ROIs, some authors described the impact of the sagittal balance (i.e., cervical lordosis and thoracic kyphosis) on the spinal cord tractography rendering (Barry et al, 2018;Dauleac et al, 2021), and reported that a greater number of artifacts is observed at the C7 level (i.e., where the cervical lordosis is the most significant) (Barry et al, 2018). Moreover, a critical angle (22 • ), above which, fibers were not tracked along the entire length of the spinal cord was defined (Dauleac et al, 2021).…”

“…Developments in both imaging acquisition and post-processing have improved the accuracy and reliability of tractography (Andersson and Sotiropoulos, 2016 ; Cohen-Adad et al, 2021a ; Dauleac et al, 2021 ), and have highlighted the potential key role of tractography, compared to classical anatomical MR sequences, for a wide range of spinal cord diseases [intramedullary tumors (Choudhri et al, 2014 ; Egger et al, 2016 ), vascular malformations (Dauleac et al, 2019a ), spinal cord injury (Chang et al, 2010 ; Rao et al, 2013 ), syringomyela (Dauleac et al, 2019b ), multiple sclerosis (Cruz et al, 2009 ; van Hecke et al, 2009 ), cervical myelopathy (Lee et al, 2011 )]. Spinal cord tractography is not currently possible in routine clinical practice because of the difficulties in producing tractograms in an accessible way, but more importantly, tridimensional renderings are not yet consistent with the anatomical truth (Dauleac et al, 2020 , 2021 ). Also, tractography results are strongly dependent upon the user who defines the parameters in all the steps of the imaging pipeline, from imaging acquisition to post-processing; this is of particular importance for the design of regions of interest (ROIs) and the elimination of spurious fibers (Roundy et al, 2012 ).…”