Orthogonal X-Ray Tracking for Respiratory Motion in Radiotherapy
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Solution Overview
Problem
Current patient positioning techniques for radiotherapy, such as image-guided radiation therapy (IGRT), face challenges in accurately accounting for respiratory motion, leading to potential misalignment of cancerous target anatomies and increased radiation exposure to healthy tissues, with existing solutions being costly or impractical for routine use.
Innovation Solution
A method and system that acquire synchronized two-dimensional x-ray image sequences from orthogonal angles, synchronized with respiratory signals, to determine three-dimensional positions of the target anatomy over time, allowing for precise alignment and tracking during radiotherapy, using a single x-ray system and internal markers for accurate dose delivery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If IGRT techniques are used to account for respiratory motion, then measurement precision of target position is improved, but device complexity increases due to need for multiple imaging modalities
Solution Approach 1:
The patent combines multiple imaging modalities (kV imaging system and MV portal imaging system) into a single integrated system that can acquire images from different energy ranges and angles. This merging allows the system to achieve high measurement precision for target position while reducing device complexity by consolidating separate imaging systems into one unified platform.
Solution Approach 2:
The imaging system is designed to perform multiple functions: it can acquire kV images for high-precision target localization, acquire MV portal images for treatment verification, and synchronize both with respiratory signals. This multi-functionality eliminates the need for separate dedicated imaging devices, thereby reducing overall system complexity while maintaining high measurement precision.
2Measurement precision
If 4D CT scanners are deployed to track respiratory motion, then measurement precision is improved, but cost increases significantly
Solution Approach 1:
Instead of deploying expensive 4D CT scanners in every treatment room, the patent uses a more cost-effective approach by acquiring multiple 2D x-ray image sequences from different angles and synthesizing 3D position information through image registration and triangulation algorithms. This copying method achieves comparable measurement precision for respiratory motion tracking at a fraction of the cost.
Solution Approach 2:
The patent replaces the mechanical 4D CT scanning system with a computational approach using 2D x-ray imaging combined with image processing algorithms. By substituting the complex mechanical 4D CT system with a lighter-weight imaging system plus sophisticated software registration and triangulation, the solution achieves similar measurement precision at lower cost.
3Ease of operation
If skin markers are used for patient positioning, then ease of operation is improved, but measurement precision deteriorates due to non-rigid connection with target anatomy
Solution Approach 1:
The patent introduces internal markers (such as fiducial markers implanted near the target) as an intermediary between the external skin markers and the actual target anatomy. These internal markers move with the target during respiratory motion, providing a reliable reference that maintains measurement precision while still allowing for relatively simple positioning procedures.
Solution Approach 2:
The patent replaces reliance on external skin markers with an image-guided system that uses internal anatomical landmarks and implanted fiducial markers detected through x-ray imaging. This substitution eliminates the fundamental problem of skin marker displacement while maintaining ease of operation through automated image-based positioning rather than manual marker alignment.
4Device complexity
If portal imaging is used for IGRT, then device complexity is reduced by using single modality, but measurement precision deteriorates due to transparency of soft tissue to high-energy beam
Solution Approach 1:
The patent merges kV imaging capability with MV portal imaging capability in a single system. The kV imaging component provides high-precision soft tissue visualization, while the MV portal imaging component provides treatment verification. By combining these two imaging modalities, the system achieves both good soft tissue visibility and maintains device simplicity through integration rather than requiring separate systems.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables accurate and cost-effective tracking of cancerous target anatomies during radiotherapy, minimizing exposure to healthy tissues by dynamically adapting radiation delivery to account for respiratory motion, improving the precision and safety of the treatment process.
Implementation Method 1
acquire a first x-ray image sequence of a target inside the patient at a first angle; acquiring a second x-ray image sequence of the target at a second angle
Data Source
AI summary
A system and method for positioning a patient for radiotherapy is provided. The method comprises: acquiring a first x-ray image sequence of a target inside the patient at a first angle; acquiring first respiratory signals of the patient while acquiring the first x-ray image sequence; acquiring a second x-ray image sequence of the target at a second angle; acquiring second respiratory signals of the patient while acquiring the second x-ray image sequence; synchronizing the first and second x-ray image sequences with the first and second respiratory signals to form synchronized first and second x-ray image sequences; identifying the target in the synchronized first and second x-ray image sequences; and determining three-dimensional (3D) positions of the target through time in the synchronized first and second x-ray image sequences.