Quantitative assessment of dMRI-based dentate-rubro-thalamic tractography in squirrel monkey

Abstract

Background: The dentate-rubro-thalamic-tract (DRTT) has recently been suggested as a new target in treatment of tremors for patients of essential tremor and Parkinson’s disease. Diffusion MRI (dMRI) tractography was reported to able to reconstruct DRTT non-invasively in human brain. However, the performance of dMRI tractography with different setups has not been rigorously evaluated, which serves as a necessary step to optimize the protocol of reconstruction. Purpose: In this study, we aim to assess the efficacy of the dMRI-based DRTT tractography by comparing with histological “ground truth” in the same brain. Method: A fixed squirrel monkey brain was scanned in 9.4T magnet with four shells (b=3000/6000/9000/12000s/mm2 ) and 100 diffusion gradient directions for each shell. Probabilistic tractography was implemented with a set of variables (i.e., b value, number of gradient directions, step length and binarization threshold), and the dMRI-derived DRTT volume was quantitatively compared with histological DRTT volume, which was obtained from Myelin stain of the same brain. Moreover, the primary orientations estimated by dMRI were compared with histological fiber orientations along the skeleton of histological DRTT. Result: The sensitivity of dMRI measure increases as the number of gradient directions increases and decreases as the binarization threshold increases. As b value increases, primary orientations estimated from dMRI agree more with histological ones along the skeleton of histological DRTT. Conclusion: Our work provides a valuable assessment of DRTT tractography, which serves as a guideline for optimization of protocol starting from image acquisition, orientation estimation to tractography.