Robust organ mapped dose: using multiple image registrations to identify deformation uncertainty in radiation dose...

Area of Science:

• Radiation Oncology
• Medical Physics
• Image-guided Therapy

Background:

• Accurate cumulative dose estimation is crucial for safe and effective reirradiation (reRT) treatment planning.
• Deformable image registration (DIR) uncertainty poses a challenge in reRT dose accumulation.
• Existing methods may not fully capture spatial uncertainties in critical organs-at-risk (OARs).

Purpose of the Study:

• To introduce a Robust Organ-Mapped Dose (ROAD) method for estimating cumulative dose in OARs during reRT.
• To incorporate voxel-level DIR uncertainty into dose estimation using a novel resampling kernel.
• To improve the reliability of OAR dose assessment in reRT, especially in areas with significant anatomical changes.

Main Methods:

• Developed a dose resampling kernel based on the discordance among three independent DIR algorithms to estimate spatial uncertainty.
• Incorporated additional kernel expansions to account for uncertainties not captured by inter-DIR discordance, ensuring dose origin and sampling within OARs.
• Applied the ROAD method to pelvic, head-and-neck, and thoracic reRT cases, comparing results with baseline mapped doses and a fixed-kernel method.

Main Results:

• The ROAD framework successfully detected residual errors beyond DIR discordance using additional kernel expansions.
• ROAD demonstrated comparable dose distributions to fixed-kernel methods under low deformation uncertainty.
• ROAD showed superior robustness in regions with large anatomical variations (e.g., pelvis), reducing underestimation of mapped near-maximum doses without increasing overall dose.

Conclusions:

• The proposed ROAD framework provides a more reliable OAR dose estimate by explicitly incorporating voxel-level DIR uncertainty.
• ROAD enhances confidence in reirradiation dose assessment, particularly in cases with substantial anatomical changes.
• The ROAD method offers a practical and robust tool for clinical evaluation of cumulative organ doses in reRT.