Inverse Planning Optimization for Radiotherapy Dose Distribution

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Solution Overview

Problem

Current inverse treatment planning methods in radiotherapy, such as those used in Gamma Knife radiosurgery, face challenges in efficiently optimizing radiation dose delivery to tumor targets while minimizing exposure to surrounding healthy tissue, particularly when multiple targets are close to each other, leading to complex optimization problems and potential adverse effects from irradiating large volumes of normal tissue.

Innovation Solution

A convex optimization method is employed to steer radiation delivery based on clinical criteria for regions of interest, including targets and organs at risk, by estimating voxel sets receiving higher doses and penalizing low-dose voxels to suppress unnecessary radiation, allowing for optimal treatment planning that adjusts beam shape settings and collimator configurations to achieve precise dose distribution.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Extent of automation

If relative isodose-based inverse planning is used, then treatment planning can be automated, but the optimization problem becomes inherently difficult to solve requiring compromise between computation time and solution quality

Engineering Contradiction:

Improveautomated treatment planningVSAvoidoptimization problem complexity

Core Design Contradiction:

Extent of automationVSDevice complexity

Solution Approach 1:

The patent transforms the optimization variables from relative isodose parameters to absolute dose parameters. This fundamental parameter change simplifies the optimization problem by directly linking the objective function to clinically relevant absolute dose values, eliminating the need for complex iterative transformations between relative and absolute dose systems.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent inverts the traditional optimization approach by formulating the problem to directly minimize a cost function based on absolute dose deviations from prescribed values, rather than iteratively adjusting relative isodose levels. This inversion of the optimization strategy simplifies the mathematical formulation and computational requirements.

Inventive Principle:

Principle #13The other way round (Inversion)

2Adaptability or versatility

If multiple targets are treated close to each other, then comprehensive cancer treatment is achieved, but radiation exposure to surrounding healthy tissue increases

Engineering Contradiction:

Improvemulti-target treatment capabilityVSAvoidradiation exposure to healthy tissue

Core Design Contradiction:

Adaptability or versatilityVSObject-affected harmful factors

Solution Approach 1:

The patent applies local quality by allowing different absolute dose prescriptions for different target volumes while using a unified optimization framework. Each target can have its own dose constraints and priorities, enabling precise control of radiation distribution in different anatomical regions while protecting surrounding healthy tissues.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent segments the treatment plan into multiple target-specific dose prescriptions, each with its own constraints and optimization weights. This segmentation allows the optimization algorithm to independently control dose delivery to each target while coordinating to minimize overall exposure to healthy tissues between targets.

Inventive Principle:

Principle #1Segmentation

3Productivity

If traditional inverse planning optimizes relative isodoses, then beam directions and collimator configurations can be determined, but the resulting dose distribution may not optimally satisfy absolute dose criteria for organs at risk

Engineering Contradiction:

Improvetreatment plan generation efficiencyVSAvoidabsolute dose accuracy

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The patent changes the fundamental optimization parameter from relative isodose to absolute dose, allowing direct control and optimization of absolute dose values delivered to targets and organs at risk. This enables the system to simultaneously achieve efficient plan generation and high precision in absolute dose delivery.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS10888711B2Methods for inverse planning

Publication Date: 2021.01.12 ELEKTA INSTRUMENT AB

AI summary

In the field of radiotherapy, methods for dose or treatment planning for a radiotherapy system are disclosed, wherein a spatial dose delivered can be adjusted and delivered radiation is determined using an optimization problem that steers the delivered radiation according to a frame description reflecting criteria for regions of interest that include at least one of targets to be treated during treatment of the patient, organs at risk and/or healthy tissue. The method includes estimating a voxel set receiving a higher dose than a predetermined threshold dose level, which voxel set includes voxels from at least one target volume. Further, a low dose voxel set is determined and a frame description for the voxels in the low dose voxel set is provided where voxels receiving a dose exceeding a predetermined threshold value is penalized such that the dose delivered to the low dose voxel set is suppressed. The frame description is then used in the optimization problem that steers the delivered radiation.