Improvement in White Matter Tract Reconstruction with Constrained Spherical Deconvolution and Track Density Mapping in Low Angular Resolution Data: A Pediatric Study and Literature Review

Abstract

IntroductionDiffusion-weighted magnetic resonance imaging (DW-MRI) allows noninvasive investigation of brain structure in vivo. Diffusion tensor imaging (DTI) is a frequently used application of DW-MRI that assumes a single main diffusion direction per voxel, and is therefore not well suited for reconstructing crossing fiber tracts. Among the solutions developed to overcome this problem, constrained spherical deconvolution with probabilistic tractography (CSD-PT) has provided superior quality results in clinical settings on adult subjects; however, it requires particular acquisition parameters and long sequences, which may limit clinical usage in the pediatric age group. The aim of this work was to compare the results of DTI with those of track density imaging (TDI) maps and CSD-PT on data from neonates and children, acquired with low angular resolution and low b-value diffusion sequences commonly used in pediatric clinical MRI examinations.Materials and methodsWe analyzed DW-MRI studies of 50 children (eight neonates aged 3–28 days, 20 infants aged 1–8 months, and 22 children aged 2–17 years) acquired on a 1.5 T Philips scanner using 34 gradient directions and a b-value of 1,000 s/mm2. Other sequence parameters included 60 axial slices; acquisition matrix, 128 × 128; average scan time, 5:34 min; voxel size, 1.75 mm × 1.75 mm × 2 mm; one b = 0 image. For each subject, we computed principal eigenvector (EV) maps and directionally encoded color TDI maps (DEC-TDI maps) from whole-brain tractograms obtained with CSD-PT; the cerebellar-thalamic, corticopontocerebellar, and corticospinal tracts were reconstructed using both CSD-PT and DTI. Results were compared by two neuroradiologists using a 5-point qualitative score.ResultsThe DEC-TDI maps obtained presented higher anatomical detail than EV maps, as assessed by visual inspection. In all subjects, white matter (WM) tracts were successfully reconstructed using both tractography methodologies. The mean qualitative scores of all tracts obtained with CSD-PT were significantly higher than those obtained with DTI (p-value < 0.05 for all comparisons).ConclusionCSD-PT can be successfully applied to DW-MRI studies acquired at 1.5 T with acquisition parameters adapted for pediatric subjects, thus providing TDI maps with greater anatomical detail. This methodology yields satisfactory results for clinical purposes in the pediatric age group.

Track density imaging in progressive supranuclear palsy: A pilot study

“…In our study, track density images of WM tracts showed a good performance in distinguishing PSP-RS patients from PD considering a whole brain voxel-based classification analysis. Of note, this study provide further evidence that CSD and TDI can be successfully applied using routine clinical MR protocols with low angular resolution and low b-value (Toselli et al, 2017). This finding is not surprising since the SCP represents probably the tracts that showed the most significant alteration in diffusion properties in PSP-RS patients compared with PD patients and controls.…”

“…Moreover, the use of the CSD provides reliable fiber orientation estimations, even in voxels comprised of multiple fiber populations, generating more robust tracts reconstruction (Calamuneri et al, 2018). Of note, this study provide further evidence that CSD and TDI can be successfully applied using routine clinical MR protocols with low angular resolution and low b-value (Toselli et al, 2017). This finding, together with the possibility to implement the TDI procedure in a fully automatic way, suggests that TDI approach may help the clinicians to better understand microstructural WM involvement in several pathologic conditions.…”

Age-related differences in white matter: Understanding tensor-based results using fixel-based analysis

“…With less diffusion sensitization, as used in this study (b = 1000 s/mm 2 ), this metric is also sensitive to extra-axonal diffusion, and therefore may also reflect axonal hindrance of extra-cellular diffusion and other microstructural factors. Nevertheless, our results, as well as those of Toselli et al (2017), demonstrate that fixelbased approaches have advantages over DTI methods when analyzing single shell data like those collected here. Furthermore, our ability to observe the results reported here using data collected in 32 gradient directions demonstrates that the results are quite robust and suggest the promise of applying this method to existing single-shell lower b-value data.…”

Global and Widespread Local White Matter Abnormalities in Juvenile Neuronal Ceroid Lipofuscinosis

“…In addition, we used constrained spherical deconvolution-based tractography in the global analyses, though its acquisition was suboptimal because the diffusion-weighting and the number of gradient orientations were relatively low. 50,51 However, fiber crossings are present in most white matter 36 and can be reliably identified with constrained spherical deconvolution. [32][33][34][35] Moreover, TBSS has limitations, for example, concerning the parameters selected by the user-that is, sensitivity, anatomic specificity, and restriction to only a part of the white matter voxels.…”