用组织混合熵加权,提升脑MRI超分辨率在边界区域的重建精度。
Tissue-Mixture Entropy-Weighted Reconstruction for Partial-Volume-Aware Brain MRI Super-Resolution

- 基于低分辨率图像构建引导机制,结合组织混合熵动态加权
- 在4倍放大下显著提升组织交界区重建质量,全图指标全面改善
- 适合关注脑部结构细节重建的研究者,尤其重视部分体积效应场景
脑MRI超分辨率中,全图目标函数会忽略受部分体积效应(PVE)影响的组织过渡区域,因这些区域仅占图像小部分。单个边界无法体现体素内脑脊液、灰质和白质的连续混合状态。本文提出AGW-PBR方法,采用仅依赖低分辨率(LR)图像的重建骨干,并在训练时引入强调组织过渡的损失函数。该骨干融合了由LR图像提取的Sobel引导、软潜在基底分配与有界网格锚定残差变形。通过注册的T1/T2/PD IXI图像固定生成高质量组织比例,转化为组织混合熵,定义经验证的PVE支持范围内的均值归一化重建权重。这些辅助信息仅用于训练,推理时仅需输入低分辨率图像。在2×、4×、6×的IXI T2加权图像上,以三组种子和受试者级配对分析进行评估。4×条件下,使用SynthSeg掩码独立评估组织界面与非界面区域的重建效果。通过消融实验考察有效支持监督、空间对齐熵加权及软潜在分配的影响。同时,该骨干也在fastMRI数据集上无PVE监督条件下从头训练。结果表明,AGW-PBR在所有测试的IXI尺度上均提升全图重建性能,且在4×下显著增强区域保真度;而无PVE监督的骨干在fastMRI上仍保持良好表现。研究支持组织混合熵加权在部分体积感知脑部MRI超分辨率中的有效性。
原文摘要 · Abstract (English)
Full-image objectives in brain magnetic resonance imaging (MRI) super-resolution (SR) can underweight tissue-transition regions affected by the partial-volume effect (PVE), as these regions occupy only a small fraction of the image. Binary boundaries also do not capture the continuous mixture of cerebrospinal fluid, gray matter, and white matter within a voxel. We propose Anatomy-Guided Gaussian-Parameter Warping with PVE-Balanced Reconstruction (AGW-PBR), which combines a low-resolution (LR)-only reconstruction backbone with a training-time objective that emphasizes tissue transitions. The backbone integrates LR-derived Sobel guidance, soft latent-basis assignment, and bounded grid-anchored residual warping. Fixed, quality-controlled tissue fractions derived from registered T1/T2/PD IXI images are converted into tissue-mixture entropy, which defines mean-normalized reconstruction weights within validated PVE support. These sidecars are used only during training, and inference requires only the LR image. AGW-PBR is evaluated on T2-weighted IXI images at 2x, 4x, and 6x using three seeds and subject-level paired analyses. At 4x, test-only SynthSeg masks independently assess reconstruction in tissue-interface and non-interface regions. Targeted ablations examine valid-support supervision, spatially aligned entropy weighting, and soft latent assignment. The AGW-backbone is also trained from scratch on fastMRI at 4x without PVE supervision. AGW-PBR improves full-image reconstruction across the tested IXI scales and regional fidelity at 4x, while the PVE-free backbone retains strong performance on fastMRI. These findings support tissue-mixture entropy weighting for partial-volume-aware brain MRI SR.
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