用Transformer直接生成放疗计划的射野强度图,更准更物理合理。
FluenceFormer: Transformer-Driven Multi-Beam Fluence Map Regression for Radiotherapy Planning
- 分两阶段建模:先预测全局剂量分布,再结合射野几何生成强度图。
- 能量误差降至4.5%,结构一致性显著提升(p<0.05)。
- 适配多种Transformer模型,对放疗自动化有实用价值。
放疗计划中的射野强度图预测是自动化放疗的核心,但因解剖结构与束流调制间的复杂关系,仍属病态逆问题。以往基于卷积的方法难以捕捉长程依赖,导致计划结构不一致或物理不可行。本文提出 extbf{FluenceFormer},一种无需特定主干网络的Transformer框架,实现直接、几何感知的射野强度回归。模型采用统一的两阶段设计:第一阶段从解剖输入预测全局剂量先验,第二阶段将此先验结合显式射野几何,回归出物理校准的强度图。核心为 extbf{Fluence-Aware Regression (FAR)}损失,融合体素级保真度、梯度平滑性、结构一致性及束流能量守恒。我们在前列腺IMRT数据集上评估了多种Transformer主干(Swin UNETR、UNETR、nnFormer、MedFormer),FluenceFormer与Swin UNETR结合表现最佳,优于现有基准CNN和单阶段方法,能量误差降低至4.5%,结构保真度提升具有统计显著性(p < 0.05)。
原文摘要 · Abstract (English)
Fluence map prediction is central to automated radiotherapy planning but remains an ill-posed inverse problem due to the complex relationship between volumetric anatomy and beam-intensity modulation. Convolutional methods in prior work often struggle to capture long-range dependencies, which can lead to structurally inconsistent or physically unrealizable plans. We introduce \textbf{FluenceFormer}, a backbone-agnostic transformer framework for direct, geometry-aware fluence regression. The model uses a unified two-stage design: Stage~1 predicts a global dose prior from anatomical inputs, and Stage~2 conditions this prior on explicit beam geometry to regress physically calibrated fluence maps. Central to the approach is the \textbf{Fluence-Aware Regression (FAR)} loss, a physics-informed objective that integrates voxel-level fidelity, gradient smoothness, structural consistency, and beam-wise energy conservation. We evaluate the generality of the framework across multiple transformer backbones, including Swin UNETR, UNETR, nnFormer, and MedFormer, using a prostate IMRT dataset. FluenceFormer with Swin UNETR achieves the strongest performance among the evaluated models and improves over existing benchmark CNN and single-stage methods, reducing Energy Error to $\mathbf{4.5\%}$ and yielding statistically significant gains in structural fidelity ($p < 0.05$).
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