Dynamic Wavelet Multi-Directional Perception and Geometry Axis-Solution Guided 3D CT Fracture Image Segmentation
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摘要: 三维骨折图像分割是临床骨科术前方案量化的关键,其中骨折面分割性能则直接影响手术决策的安全性与有效性。针对三维骨折图像分割中存在深层全局特征捕获不足、骨折面细节方向纹理模糊以及骨折图像几何结构利用不充分的问题,该文提出动态小波多向感知与几何轴解引导的三维CT骨折图像分割方法(Dynamic Wavelet Multi-Directional Perception and Geometry Axis-Solution Guided Network, DWAG-Net)。首先,为充分提取多维度视角下全局特征,设计动态可学习参数插值重构三平面视角特征,并与全维特征聚合实现多维度提取骨折图像全局信息。其次,引入三维小波变换,通过各方向高频子带的跨子带特征融合,增强模型对模糊骨折面中方向特征的纹理细节感知。最后,根据骨骼结构相似性与骨折面局部突变性设计几何轴解引导模块,通过几何亲和与距离衰减引导模型轴解分割,并重新分配类别权重缓解其不平衡问题,约束损失函数梯度向最优方向下降。在自建胫骨骨折数据集上,DWAG-Net模型相比现有先进模型展现出优越分割性能,平均Dice Score为71.20%其中骨折面类较基准提升了7.12%,平均HD95为1.38 mm其中骨折面类降低了3.70 mm,与前沿3D分割算法nnWNet相比平均Dice Score提升了4.63%。实验结果表明,DWAG-Net模型可有效实现三维骨折图像分割任务,为术前穿钉角度量化与固定位置精确选择提供了图像依据,对辅助医生优化术前方案具有重要意义。Abstract:
Objective Accurate segmentation of fracture surfaces in 3D CT images is critical for orthopedic surgical planning, particularly in determining optimal nail insertion angles perpendicular to fracture planes. However, existing methods exhibit three key limitations: insufficient capture of deep global volumetric context, directional texture ambiguity in low-contrast fracture regions, and underutilization of geometric features decoding. To overcome these challenges, we propose DWAG-Net, a novel framework that integrates Dynamic Wavelet Perception and Geometry-Axis Guidance, to significantly enhance segmentation precision for complex tibial fractures and provide reliable 3D digital guidance for preoperative planning. Methods The architecture extends 3D nnU-Netv2 with three core innovations. First, the Dynamic Multi-View Aggregation (DMVA) module dynamically fuses tri-planar (axial/sagittal/coronal) and full-volume features via learnable parameter interpolation (optimized kernel size: 2×2×2) and channel-wise Hadamard product, enhancing global context modeling. Second, the Wavelet Direction Perception Enhancement (WDPE) module decomposes inputs using 3D Symlets discrete wavelet transform and applies direction-specific enhancement to eight subbands: adaptive convolutional kernels (e.g., [5,3,3] for depth-dominant fractures) amplify texture details in high-frequency subbands, while cross-subband fusion strategies integrate complementary features. Third, the Geometry Axis-Solution Guided (GASG) module embeds in decoders to enforce anatomical consistency by computing axis-level affinity maps (depth/height/width) that combine geometric similarity with spatial distance decay, and by optimizing boundary delineation through rotational positional encoding and multi-axis attention. The model was trained on the YN-TFS dataset (110 tibial fracture CT scans, resolution 0.39–1.00 mm) using SGD optimizer (lr=0.01, momentum=0.99) and a class-weighted loss (background:0.5, bone:1, fracture:5) to mitigate severe pixel imbalance. Results and Discussions DWAG-Net achieved state-of-the-art performance, with a mean Dice score of 71.20% ( Table 1 ), surpassing nnU-Netv2 by 5.06% (fracture surface Dice: 69.48%, +7.12%). Boundary precision improved significantly, yielding a mean HD95 of 1.38 mm (fracture surface: 1.54 mm, –3.70 mm). Ablation studies (Table 2 ) confirmed each module’s contribution: DMVA improved Dice by 2.40% through adaptive multi-view fusion; WDPE resolved directional ambiguity, adding a 5.84% fracture-surface Dice gain; GASG provided a further 1.20% gain by enforcing geometric consistency. Key configurations included optimal DMVA parameters (2×2×2), Symlets wavelets, and sequential axis processing (D→H→W). Qualitatively, DWAG-Net preserved fracture integrity where U-Mamba/nnWNet failed and reduced over-segmentation compared with nnFormer/UNETR++ (Fig. 4 ).Conclusions DWAG-Net establishes a new state-of-the-art for 3D fracture segmentation by synergizing multi-directional wavelet perception and geometric guidance. Its key innovations—DMVA for volumetric context fusion, WDPE for directional texture enhancement, and GASG for anatomically consistent decoding—deliver clinically critical precision (71.20% Dice, 1.38 mm HD95) and enable data-driven surgical planning. Future work will focus on optimizing loss functions for severe class imbalance. -
表 1 不同模型的分割性能对比
模型 年份 Dice Score/% HD95/mm FLOPs/G Params/M Inference/s Avg 骨骼 骨折面 Avg 骨骼 骨折面 nnU-Netv2 2023 66.14 69.93 62.36 3.68 2.12 5.24 561.92 30.79 124.00 nnFormer 2023 55.13 50.79 59.47 98.99 137.85 60.12 47.70 37.15 218.97 UNETR++ 2024 51.13 46.42 55.84 103.39 137.97 68.80 43.70 66.80 213.56 U-Mamba 2024 68.86 71.38 66.35 5.10 6.19 4.02 1141.86 42.12 115.95 nnWNet 2025 66.57 66.98 66.15 1.94 1.77 2.11 1378.62 60.46 123.09 DWAG-Net 2025 71.20 72.91 69.48 1.38 1.22 1.54 675.22 57.60 159.48 表 2 所提出的模块对分割精度的影响
模型 模块 Dice Score /% HD95 / mm DMVA WDPE GASG Avg 骨骼 骨折面 Avg 骨骼 骨折面 基准 66.15 69.93 62.36 3.68 2.12 5.24 Ours1 √ 68.55 70.30 66.79 2.04 2.27 1.81 Ours2 √ 67.50 67.21 67.79 1.84 1.92 1.75 Ours3 √ √ 70.00 71.80 68.20 1.53 1.27 1.79 DWAG-Net √ √ √ 71.20 72.91 69.48 1.38 1.22 1.54 表 3 DMVA与WDPE编码位置对分割精度的影响
DMVA(√)与WDPE(O)嵌入位置 Dice Score /% HD95 / mm 3 4 5 Avg 骨骼 骨折面 Avg 骨骼 骨折面 √ O √ O 69.72 72.51 66.92 1.50 1.22 1.78 √ O √ O 68.75 72.57 64.92 1.77 1.25 2.29 √ √ O O 68.43 70.82 66.03 1.55 1.32 1.77 √ O O √ 67.06 68.59 65.53 2.03 2.15 1.90 √ O √ O 67.92 71.02 64.82 1.71 1.63 1.79 √ O √ O 70.00 71.80 68.20 1.53 1.27 1.79 O √ O √ 67.56 69.92 65.20 1.67 1.58 1.76 O √ √ O 68.49 70.88 66.09 1.55 1.31 1.79 √ O √ O 67.70 69.40 66.00 2.04 2.30 1.78 表 4 DMVA模块中动态可学习参数大小对分割精度的影响
动态可学习参数大小 Dice Score /% HD95 / mm Avg 骨骼 骨折面 Avg 骨骼 骨折面 1×1×1 65.03 68.09 61.96 4.34 4.23 4.45 2×2×2 68.55 70.30 66.79 2.04 2.27 1.81 3×3×3 66.28 68.76 63.80 3.10 2.81 3.38 4×4×4 65.58 68.30 62.85 3.72 2.66 4.77 5×5×5 66.57 70.09 63.04 3.54 2.31 4.76 表 5 不同小波基对分割精度的影响
小波基类型 Dice Score/% HD95 / mm Avg 骨骼 骨折面 Avg 骨骼 骨折面 Haar 67.14 67.98 66.29 1.75 1.69 1.80 Daubechies 67.91 68.20 67.62 1.66 1.57 1.75 Coiflets 67.36 69.24 65.47 1.71 1.49 1.92 Biorthogonal 68.33 69.54 67.12 1.69 1.35 2.02 Symlets 67.50 67.21 67.79 1.84 1.92 1.75 Reverse Biorthogonal 69.35 71.64 67.06 1.58 1.27 1.89 表 6 GASG中不同轴解顺序对分割精度的影响
轴解顺序 Dice Score /% HD95 / mm Avg 骨骼 骨折面 Avg 骨骼 骨折面 D→H→W 71.20 72.91 69.48 1.38 1.22 1.54 D→W→H 69.75 72.10 67.39 1.73 1.69 1.76 H→D→W 69.08 70.89 67.28 1.54 1.36 1.71 H→W→D 68.24 70.12 66.35 1.70 1.60 1.80 W→D→H 67.11 67.28 66.93 3.34 4.90 1.77 W→H→D 69.64 71.13 68.14 1.54 1.36 1.72 表 7 不同损失权重比例对分割精度的影响
损失权重比例 Dice Score /% HD95 / mm Avg 骨骼 骨折面 Avg 骨骼 骨折面 1:1:1 70.64 73.40 67.88 2.35 1.20 3.50 0.7:1:5 70.27 72.47 68.06 1.44 1.28 1.59 0.5:1:3 70.27 73.06 67.47 1.63 1.47 1.79 0.5:1:5 71.20 72.91 69.48 1.38 1.22 1.54 0.5:1:7 69.70 71.45 67.94 1.65 1.64 1.65 0.3:1:5 71.13 73.07 69.18 1.43 1.28 1.57 -
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