Tools for the analysis of dose optimization: III. Pointwise sensitivity and perturbation analysis

Area of Science:

• Medical Physics
• Radiation Oncology
• Computational Biology

Background:

• Intensity-modulated radiotherapy (IMRT) planning requires balancing tumor control and normal tissue sparing.
• Achieving the ideal balance is often unfeasible, necessitating compromises through constrained optimization.
• Previous work addressed cost functions; this study introduces spatial resolution.

Purpose of the Study:

• To integrate spatial resolution into the formalism of constrained optimization for IMRT.
• To quantitatively predict the impact of constraint adjustments on optimal dose distribution.
• To identify specific constraints responsible for underdosing in selected target subvolumes.

Main Methods:

• Development of a formalism incorporating spatial resolution into constrained optimization.
• Identification of active constraints within user-defined target subvolumes with insufficient dose.
• Prediction of the optimal dose distribution's response to constraint perturbations.

Main Results:

• The method successfully reveals active constraints contributing to dose deficits in target subvolumes.
• It provides a quantitative prediction of how dose distributions change with constraint adjustments.
• Demonstrated utility through a clinical example.

Conclusions:

• Introducing spatial resolution enhances the understanding of constraint impacts in IMRT planning.
• This approach aids in diagnosing and resolving issues related to underdosed regions.
• Facilitates more precise and effective radiotherapy treatment planning.