Impact of gradient number and voxel size on DTI tractography for resective brain surgery.

Impact of gradient number and voxel size on DTI tractography for resective brain surgery.

World Neurosurg. 2017 Jun 14;:

Authors: Hoefnagels FWA, de Witt Hamer PC, Pouwels PJW, Barkhof F, Vandertop WP

Abstract
OBJECTIVE: To explore quantitatively and qualitatively how the number of gradient directions (NGD) and spatial resolution (SR) affect DTI-tractography in patients planned for brain tumor surgery, using routine clinical MR-imaging protocols.
METHODS: Of 67 patients with intracerebral lesions who had two different DTI-scans, three DTI-series were reconstructed to compare the effects of NGD and SR. Tractographies for four clinically relevant tracts (corticospinal tract, superior longitudinal fasciculus, optic radiation and inferior fronto-occipital fasciculus) were constructed with a probabilistic tracking algorithm and automated ROI-placement and compared for three quantitative measurements: tract volume, median fiber density and mean FA, using linear mixed-effects models. The mean tractography volume and intersubject reliability were visually compared across scanning protocols, to assess the clinical relevance of the quantitative differences.
RESULTS: Both NGD and SR significantly influenced tract volume, median fiber density and mean FA, but not to the same extent. Especially higher NGD increased tract volume and median fiber density. More importantly, these effects further increased when tracts were affected by pathology. The effects were tract-specific, but not dependent on threshold. The superior longitudinal fasciculus and inferior fronto-occipital fasciculus showed the most significant differences. Qualitative assessment showed larger tract volumes given a fixed confidence level, and better intersubject reliability for the higher NGD-protocol. SR in the range we considered seemed less relevant than NGD.
CONCLUSION: The current study indicates that, under time constraints of clinical imaging, a higher number of diffusion gradients is more important than spatial resolution for superior DTI probabilistic tractography in patients undergoing brain tumor surgery.

PMID: 28624562 [PubMed - as supplied by publisher]

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