Abstract
Background and PurposeImaging the optic radiation (OR) is of considerable interest in studying diseases affecting the visual pathway and for pre-surgical planning of temporal lobe resections. The purpose of this study was to investigate the clinical feasibility of using probabilistic diffusion tractography based on constrained spherical deconvolution (CSD) to image the optic radiation. It was hypothesized that CSD would provide improved tracking of the OR compared with the widely used ball-and-stick model.MethodsDiffusion weighted MRI (30 directions) was performed on twenty patients with no known visual deficits. Tractography was performed using probabilistic algorithms based on fiber orientation distribution models of local white matter trajectories. The performance of these algorithms was evaluated by comparing computational times and receiver operating characteristic results, and by correlation of anatomical landmark distances to dissection estimates.ResultsThe results showed that it was consistently feasible to reconstruct individual optic radiations from clinically practical (4.5 minute acquisition) diffusion weighted imaging data sets using CSD. Tractography based on the CSD model resulted in significantly shorter computational times, improved receiver operating characteristic results, and shorter Meyer’s loop to temporal pole distances (in closer agreement with dissection studies) when compared to the ball-and-stick based algorithm.ConclusionsAccurate tractography of the optic radiation can be accomplished using diffusion MRI data collected within a clinically practical timeframe. CSD based tractography was faster, more accurate and had better correlation with known anatomical landmarks than ball-and-stick tractography.
Highlights
The optic radiation (OR) is a fan-like white matter structure which originates in the lateral geniculate nucleus (LGN) and terminates posteriorly in the calcarine sulcus of the occipital lobe
The purpose of this study was to investigate the clinical feasibility of using probabilistic diffusion tractography based on constrained spherical deconvolution (CSD) to image the optic radiation
The results showed that it was consistently feasible to reconstruct individual optic radiations from clinically practical (4.5 minute acquisition) diffusion weighted imaging data sets using CSD
Summary
The optic radiation (OR) is a fan-like white matter structure which originates in the lateral geniculate nucleus (LGN) and terminates posteriorly in the calcarine sulcus of the occipital lobe. The most anterior section of the OR, Meyer’s loop, remains a challenge to define due to the sharp angulation and reduced fiber density in this area compared to the body of the OR These factors predispose tractography algorithms to terminate in this region, or to generate erroneous tracts. Many prior studies [6,7,18] have utilized acquisition protocols with a large number of diffusion sensitizing directions which allow for sophisticated diffusion modeling and subsequently better tractography results. The disadvantage of this approach is the long acquisition time (between 10–30 minutes). It was hypothesized that CSD would provide improved tracking of the OR compared with the widely used ball-and-stick model
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