A fast and Generic Energy-Shifting Transformer for Hybrid Monte Carlo Radiotherapy Calculation

We introduce a novel learning framework for accelerated Monte Carlo (MC) dose calculation termed Energy-Shifting. This approach leverages deep learning to synthesize 6 MV TrueBeam Linear Accelerator (LINAC) dose distributions directly from monoenergetic inputs under identical beam configurations. Unlike conventional denoising techniques, which rely on noisy low-count dose maps that compromise beam profile integrity, our method achieves superior cross-domain generalization on unseen datasets by integrating high-fidelity anatomical textures and source-specific beam similarity into the model's input space. Furthermore, we propose a novel 3D architecture termed TransUNetSE3D, featuring Transformer blocks for global context and Residual Squeeze-and-Excitation (SE) modules for adaptive channel-wise feature recalibration. Hierarchical representations of these blocks are fused into the network's latent space alongside the primary dose-map parameters, allowing physics-aware reconstruction. This hybrid design outperforms existing UNet and Transformer-based benchmarks in both spatial precision and structural preservation, while maintaining the execution speed necessary for real-time use. Our proposed pipeline achieves a Gamma Passing Rate exceeding 98% (3%/3mm) compared to the MC reference, evaluated within the framework of a treatment planning system (TPS) for prostate radiotherapy. These results offer a robust solution for fast volumetric dosimetry in adaptive radiotherapy.

Machine Learning-Based Modeling of the Anode Heel Effect in X-ray Beam Monte Carlo Simulations

This study enhances Monte Carlo simulation accuracy in X-ray imaging by developing an AI-driven model for the anode heel effect, achieving improved beam intensity distribution and dosimetric precision. Through dynamic adjustments to beam weights on the anode and cathode sides of the X-ray tube, our machine learning model effectively replicates the asymmetry characteristic of clinical X-ray beams. Experimental results reveal dose rate increases of up to 9.6% on the cathode side and reductions of up to 12.5% on the anode side, for energy levels between 50 and 120 kVp. These experimentally optimized beam weights were integrated into the OpenGATE and GGEMS Monte Carlo toolkits, significantly advancing dosimetric simulation accuracy and the image quality which closely resembles the clinical imaging. Validation with fluence and dose actors demonstrated that the AI-based model closely mirrors clinical beam behavior, providing substantial improvements in dose consistency and accuracy over conventional X-ray models. This approach provides a robust framework for improving X-ray dosimetry, with potential applications in dose optimization, imaging quality enhancement, and radiation safety in both clinical and research settings.