Practical gEUD optimization technique for stereotactic radiation therapy based on a theoretical reinterpretation...

Area of Science:

• Radiation Oncology
• Medical Physics
• Radiotherapy Optimization

Background:

• Generalized Equivalent Uniform Dose (gEUD) is crucial for radiotherapy dose optimization, especially for normal tissues.
• Clinical application of gEUD often lacks theoretical clarity, leading to empirical use.
• Stereotactic Radiation Therapy (SRT) requires precise dose control for bone and spinal metastases.

Purpose of the Study:

• To reformulate gEUD-based optimization within a theoretical framework using the gEUD curve concept.
• To develop a robust optimization strategy for SRT, focusing on bone and spinal metastases.
• To introduce multiple gEUD objective (MgEUDO) and selective gEUD objective (SgEUDO) methods.

Main Methods:

• Interpreted gEUD as a smooth function of its a-parameter, creating a continuous curve.
• Proposed MgEUDO for optimizing remaining volume at risk (RVR) and SgEUDO for critical organs at risk (OARs).
• Retrospectively evaluated these methods in 22 patients undergoing five-fraction SRT (35 Gy).

Main Results:

• Achieved clinically favorable dose distributions using consistent gEUD-based optimization.
• Reduced mean dose to surrounding tissues by 10% compared to conventional normal tissue objective (NTO) constraints.
• Improved tumor dose coverage by 0.6% and achieved significant mean dose reductions in kidneys (39% left, 37.5% right) with SgEUDO.

Conclusions:

• Theoretical and practical refinement of gEUD optimization allows systematic control of dose distribution.
• Reduced inter-planner variability in radiotherapy planning.
• Combined MgEUDO and SgEUDO strategies offer a generalizable and clinically effective framework for high-precision radiotherapy.