Robust IMPT Planning via Normalized Dose Interval Histograms
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Solution Overview
Problem
Intensity-modulated proton therapy (IMPT) is sensitive to patient setup and range uncertainties, leading to challenges in balancing plan robustness and nominal plan quality, with existing robust optimization methods being inefficient and impractical for clinical use due to extensive computation requirements and unclear relationships between penalty weights and robustness.
Innovation Solution
A method using normalized dose interval volume histograms (NDIVH) to quantify plan robustness, allowing users to adjust the tradeoff between nominal plan quality and robustness by applying normalized dose interval volume constraints, which calculates the area under the NDIVH curve to determine plan robustness and balances radiation therapy plan robustness and quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If voxel-wise worst-case robust optimization is used to achieve robust IMPT plans, then plan robustness is improved, but computation time increases significantly making it impractical for clinical use
Solution Approach 1:
The patent transforms the robust optimization problem by changing parameters from voxel-wise worst-case analysis to a global approach using normalized dose interval volume histograms. Instead of optimizing each voxel independently under worst-case scenarios (which requires extensive computation), the method aggregates dose variations across all voxels into a unified histogram representation, enabling clinical-scale computation while maintaining robustness assessment capability
Solution Approach 2:
The patent extracts the essential information about dose variations from the complex voxel-wise worst-case calculations and represents it through normalized dose interval volume histograms. This extraction process captures the critical robustness characteristics without retaining the computational complexity of the original worst-case optimization, allowing for efficient clinical application
2Adaptability or versatility
If penalty weight of plan robustness term is altered to change robustness of the resulting plan, then plan robustness can be adjusted, but the quantitative relationship between penalty weight and robustness is unclear and varies among different cases
Solution Approach 1:
The patent implements a feedback mechanism where the normalized dose interval volume histogram directly quantifies the robustness of the treatment plan in terms of dose variation. This histogram provides a clear, quantitative feedback on how robust the plan is, eliminating the need to interpret complex penalty weights. The feedback is case-specific and provides actionable information about the actual dose variation characteristics of each plan
3Reliability
If additional margins are adopted to CTV to form PTV to ensure dose coverage, then dose coverage of CTV is improved, but normal tissues may be irradiated more or target may be under-dosed
Solution Approach 1:
The patent applies local quality by analyzing and controlling dose variations specifically in regions of interest (tumors and critical structures) through the normalized dose interval volume histogram. Instead of applying uniform margins throughout the entire field, the method identifies and addresses local dose variation patterns, allowing for precise control of dose coverage in critical areas while sparing normal tissues from unnecessary irradiation
Data Source
AI summary
Robust optimization systems and methods are provided for intensity modulated proton therapy (IMPT) that may be deployed in a clinically practical way to enable users to control the balance between nominal plan quality and plan robustness in a user-defined way. The method may include a normalized dose interval volume histogram (NDIVH)-based robust optimization, where the normalized dose interval (NDI) is calculated for each voxel considering dose variations in the face of uncertainties. It is then used to create a NDIVH. The area under this NDIVH curve may then be used to quantify plan robustness. By using normalized dose interval volume constraints (NDIVC) to control the shape of the NDIVH curves, plan robustness may be adjusted. The tradeoff between nominal plan quality and plan robustness can be modified in a user-defined way by adjusting positions of the NDIVCs on the NDIVH curves.