<p>Accurate pancreatic segmentation in computed tomography (CT) remains challenging due to irregular morphology, low contrast, and blurred boundaries. Most segmentation backbones produce discrete, fixed-grid voxel predictions, which can lead to coarse contours and limited representation of subtle, continuous anatomical deformations. To mitigate this limitation, IRM-UNet is introduced as a backbone-agnostic refinement framework that augments segmentation backbones with an implicit neural representation (INR) module for sub-voxel boundary refinement. The main innovations are as follows: (1) <b>Continuous boundary reconstruction</b>: modeling pancreatic morphology in a continuous domain via an INR enables accurate delineation of complex boundaries; (2) <b>Multi-scale feature fusion and uncertainty-aware sampling</b>: multi-scale feature integration with uncertainty-aware sampling concentrates refinement on low-contrast and ambiguous regions, improving robustness; and (3) <b>High-frequency detail enhancement</b>: combining positional encoding with Fourier feature mapping projects low-dimensional coordinates into a higher-dimensional space, facilitating the representation of high-frequency boundary details. Experiments on the NIH pancreatic CT dataset yield a Dice coefficient of <InlineEquation ID="IEq1"> <EquationSource Format="TEX">\(89.87 \pm 1.82\%\)</EquationSource> </InlineEquation> and a Jaccard index of <InlineEquation ID="IEq2"> <EquationSource Format="TEX">\(81.60 \pm 1.65\%\)</EquationSource> </InlineEquation>. Additional experiments indicate that the implicit refinement module functions as a plug-and-play component across different backbones and is associated with improved boundary quality.</p>

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IRM-UNet: backbone-agnostic implicit refinement for enhanced pancreatic CT segmentation

  • Chaohui Zhang,
  • Anusha Achuthan

摘要

Accurate pancreatic segmentation in computed tomography (CT) remains challenging due to irregular morphology, low contrast, and blurred boundaries. Most segmentation backbones produce discrete, fixed-grid voxel predictions, which can lead to coarse contours and limited representation of subtle, continuous anatomical deformations. To mitigate this limitation, IRM-UNet is introduced as a backbone-agnostic refinement framework that augments segmentation backbones with an implicit neural representation (INR) module for sub-voxel boundary refinement. The main innovations are as follows: (1) Continuous boundary reconstruction: modeling pancreatic morphology in a continuous domain via an INR enables accurate delineation of complex boundaries; (2) Multi-scale feature fusion and uncertainty-aware sampling: multi-scale feature integration with uncertainty-aware sampling concentrates refinement on low-contrast and ambiguous regions, improving robustness; and (3) High-frequency detail enhancement: combining positional encoding with Fourier feature mapping projects low-dimensional coordinates into a higher-dimensional space, facilitating the representation of high-frequency boundary details. Experiments on the NIH pancreatic CT dataset yield a Dice coefficient of \(89.87 \pm 1.82\%\) and a Jaccard index of \(81.60 \pm 1.65\%\) . Additional experiments indicate that the implicit refinement module functions as a plug-and-play component across different backbones and is associated with improved boundary quality.