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This paper presents a novel hybrid framework that integrates reinforcement learning with supervised learning to enhance targeted white matter tractography, a critical method for mapping brain connectivity. By eliminating the need for ground-truth fibers and explicit segmentation, the proposed approach simplifies the tractography pipeline while improving accuracy and robustness through data-driven multi-policy fusion. Extensive validation on benchmark datasets demonstrates the framework's ability to generalize across diverse data sources and accurately reconstruct white matter tracts, addressing long-standing challenges in neuroimaging.
Bypassing ground-truth dependencies, this framework achieves unprecedented accuracy in white matter tractography through a novel hybrid reinforcement and supervised learning approach.
Fiber tractography's ability to reconstruct the brain's structural pathways, has made it a crucial component of modern neuroimaging, enabling detailed, non-invasive mapping of structural connectivity and supporting a wide range of neurological research and clinical applications. However, despite its importance, tractography remains a challenging task due to the inherent complexity of white matter structure and its susceptibility to false positives, which can lead to the misrepresentation of critical pathways. To overcome these limitations, in this thesis, we propose a hybrid framework that integrates reinforcement learning with supervised learning for refining RL policies, specifically tailored for tract-specific tractography. Notably, our framework does not rely on ground-truth fibers for training. Moreover, the tract-specific formulation bypasses the need for an explicit segmentation process, simplifying the overall pipeline. Our work includes two main contributions, each building upon the previous. First, we introduce a hybrid approach that combines reinforcement learning with supervised learning (specifically, GPT-based policy learning) to refine policies in a tract-specific context. Second, we propose a scalable framework for data-driven multi-policy fusion, which leverages the complementary strengths of multiple RL policies to improve tractography performance and robustness. We demonstrate the effectiveness of our framework through extensive validation on benchmark public datasets including TractoInferno, HCP, and ISMRM-2015, highlighting its ability to generalize across data sources and accurately reconstruct brain white matter tracts. We believe that these contributions represent significant advancements in the field of tractography, improving robustness, reliability, and accuracy while reducing dependence on ground-truth annotations.
