Tomosynthesis Motion Tracking for Radiation Therapy
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Solution Overview
Problem
Current radiation therapy systems face challenges in accurately tracking target region movement during treatment due to limitations in image quality and speed, particularly caused by patient motion and noise in existing CT and 3D point tracking methods, which can lead to inaccuracies in radiation beam alignment.
Innovation Solution
A treatment system utilizing tomosynthesis for real-time motion tracking, where a second radiation source mounted orthogonally to the treatment beam acquires projection radiographs at regular intervals, allowing for continuous monitoring and adjustment of the radiation source and collimator blades to maintain accurate targeting, even during arc-therapies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If CT imaging is used to track target region movement, then 3D localization information can be obtained, but the imaging process takes too long to provide real-time data for treatment adjustment
Solution Approach 1:
The patent segments the continuous CT imaging process into discrete projection radiograph acquisitions at specific gantry angles. Instead of performing a complete 360-degree CT scan, the system acquires a limited number of projections (e.g., 3-5 images at 60-120 degree intervals) and reconstructs 3D marker positions from these segmented views, dramatically reducing imaging time while maintaining localization accuracy.
Solution Approach 2:
The system performs partial CT action by acquiring only the necessary projection radiographs at strategically selected angles rather than a full rotational scan. This partial acquisition provides sufficient 3D information for marker localization without the time penalty of complete tomographic reconstruction, enabling real-time tracking during treatment delivery.
2Measurement precision
If 3D point tracking with high density fiducial markers is used, then marker localization can be performed, but treatment must be interrupted to reposition multi-leaf collimator blades when markers are not exposed
Solution Approach 1:
The patent introduces an orthogonal kV imaging system as an intermediary that can detect markers from a different angular perspective. When the treatment beam's-eye-view cannot expose the markers, the orthogonal kV source provides an alternative viewing angle, allowing continuous marker tracking without treatment interruption. This mediator system ensures uninterrupted arc therapy delivery.
Solution Approach 2:
The system transitions from single-beam's-eye-view imaging to multi-dimensional imaging by adding an orthogonal kV imaging dimension. This dimensional change allows marker detection from multiple spatial perspectives simultaneously, ensuring that at least one imaging angle can always detect the moving markers during arc therapy, eliminating treatment interruptions.
3Measurement precision
If MV energy beam's-eye-view imaging is used for motion tracking, then treatment beam alignment can be monitored, but dose efficiency is reduced compared to kV energy imaging
Solution Approach 1:
The patent applies local quality by using different energy levels for different imaging purposes: kV energy for high-dose-efficiency marker localization and orthogonal views, and MV energy only when beam's-eye-view monitoring is absolutely necessary. This localized energy selection optimizes dose efficiency while maintaining sufficient alignment accuracy.
Solution Approach 2:
The system dynamically changes the energy parameter of the imaging system, switching between kV and MV ranges based on treatment phase and marker visibility requirements. By adjusting this fundamental parameter, the system achieves optimal dose efficiency during setup and tracking while maintaining adequate beam alignment monitoring capability.
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 enhances dose efficiency and accuracy by providing real-time 3D information for precise radiation delivery, minimizing interruptions and improving the quality of radiation therapy by continuously tracking target region movement.
Implementation Method 1
The x-ray source generates and directs an x-ray beam towards the patient, while the detector apparatus measures the x-ray absorption at a plurality of transmission paths defined by the x-ray beam during the process
Implementation Method 2
A treatment system utilizing tomosynthesis for real-time motion tracking, where a second radiation source mounted orthogonally to the treatment beam acquires projection radiographs at regular intervals
Data Source
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AI summary
One embodiment of the present disclosure sets forth a method for determining a movement of a target region using tomosynthesis. The method includes the steps of accessing a first set of projection radiographs of the target region over a first processing window defined by a first range of projection angles, accessing a second set of projection radiographs of the target region over a second processing window defined by a second range of projection angles, wherein the first processing window moves to the second processing window, and comparing a first positional information derived from the first set of the projection radiographs and a second positional information derived from the second set of the projection radiographs with the first positional information to determine the movement of the target region.