Fully automated pipeline for the fiber tractography of the anterior optic pathway in patients with sellar and parasellar tumors and analysis of the microstructural alterations

Compared to conventional morphological MR imaging, diffusion tractography may improve the visualization of the anterior optic pathway (AOP), thus enhancing the understanding of its anatomical relationship with surrounding sellar/parasellar tumors (SPTs). We aimed to develop a diffusion tractography pipeline for automatic and reliable reconstruction of the AOP and to investigate its microstructural alterations in SPT patients. A multishell diffusion protocol (b-values = 0,300,1000,2000 s/mm2; 64 maximum gradient directions; 2-mm isotropic voxel) on a 3T scanner, followed by a fully automated pipeline developed in-house to perform the probabilistic tractography, based on multishell-multitissue constrained spherical deconvolution modeling of the signal, was performed. It was first tested retrospectively in 10 healthy controls, then prospectively applied in 25 additional healthy controls and 35 SPTs patients. Microstructural parameters were compared between patients and controls using an along-tract approach. The study included 70 subjects: 35 healthy controls (18 females, mean age 50.7 ± 14.3 years) and 35 patients with SPTs displacing the optic chiasm (18 females; mean age 53.7 ± 16.4 years). The AOP reconstruction was successfully performed in all normal controls and patients. A correct correspondence with surgical inspection was identified in 84.7 % of patients who underwent surgery. Patients had significantly lower mean diffusivity (MD) values at the level of the chiasm (p < 0.01), that correlated with supero-inferior chiasmatic displacement (R = -0.49, p = 0.01). A novel, fully automated diffusion tractography pipeline for the AOP was developed and validated in patients with sellar/parasellar tumors. Reduced MD values at the chiasm level may indicate compression or gliosis in case of displacement.