Tomosynthesis Motion Tracking for Radiation Therapy
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Solution Overview
Problem
Current radiation therapy systems face challenges in accurately tracking target regions during treatment due to intra-fraction motion caused by patient shifts or physiological processes, as existing imaging techniques like CT and 3D point tracking are not sufficiently fast or accurate, leading to suboptimal radiation beam alignment.
Innovation Solution
A treatment system utilizing tomosynthesis to determine target region movement by acquiring and processing projection radiographs in real-time, allowing for continuous adjustment of the radiation beam during treatment, with a control system that adjusts the radiation source and gantry rotation based on 3D information from markers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If CT imaging is used to track target region movement, then measurement precision is improved, but productivity deteriorates due to long data collection time
Solution Approach 1:
The patent extracts only the essential information needed for motion tracking (marker positions in projection radiographs) rather than performing complete CT image reconstruction. By focusing on detecting fiducial markers in 2D projections and triangulating their 3D positions, the system achieves adequate localization precision without the time-consuming full volumetric reconstruction of CT, thus resolving the contradiction between measurement precision and productivity
Solution Approach 2:
Instead of performing complete 360-degree CT scans, the patent uses a limited number of projection radiographs taken at specific angles to track marker positions. This partial action approach provides sufficient information for real-time motion tracking while dramatically reducing acquisition time compared to full CT protocols
2Measurement precision
If 3D point tracking with fiducial markers is used, then measurement precision may be improved, but reliability deteriorates due to detection failure
Solution Approach 1:
The patent uses fiducial markers as intermediary objects that are easily detectable in projection radiographs. These markers serve as reliable intermediaries between the imaging system and the target region, providing consistent detection signals that overcome the reliability issues of direct anatomical landmark identification. The markers act as mediators that translate complex anatomical structures into simple, detectable geometric features
Solution Approach 2:
The patent employs high-contrast fiducial markers that appear as distinct bright spots or geometric features in X-ray projections. These markers have radiographic properties (high density, specific shapes) that make them stand out clearly against surrounding tissues, enabling reliable automatic detection and localization even in noisy images, thus improving both precision and reliability
3Ease of operation
If beam's-eye view imaging at MV energies is used, then ease of operation is improved, but use of energy deteriorates due to lower dose efficiency
Solution Approach 1:
The patent utilizes the treatment linac to perform both treatment delivery and imaging functions. The same MV imaging system used for beam's-eye view imaging is integrated with the treatment beam, allowing the system to switch between treatment and imaging modes without requiring separate equipment. This multi-functionality maintains ease of operation while enabling the use of more dose-efficient kV imaging when needed
Solution Approach 2:
The patent employs parameter changes by switching between different imaging energies (MV and kV) depending on the clinical situation. The system can operate in MV beam's-eye view mode for routine monitoring where ease of operation is prioritized, and switch to kV tomosynthesis mode when higher dose efficiency is required, thus dynamically optimizing the energy parameter based on operational needs
4Measurement precision
If full CT acquisition is performed, then measurement precision is improved, but loss of time increases due to motion-related degradation
Solution Approach 1:
The patent performs preliminary action by acquiring projection radiographs continuously or at frequent intervals during treatment. This ongoing acquisition of projection data allows the system to track marker positions in near real-time, capturing motion information before it degrades image quality. The continuous projection acquisition serves as a preliminary measure that enables subsequent rapid reconstruction without requiring lengthy CT scans during treatment
Solution Approach 2:
The patent segments the imaging task into two distinct components: (1) continuous acquisition of projection radiographs at multiple angles, and (2) on-demand reconstruction of tomosynthesis images or extraction of marker positions. This segmentation allows the system to collect data rapidly in projection mode without the time penalty of full reconstruction, then selectively reconstruct only when needed, thus reducing overall acquisition time while maintaining precision
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
Enables accurate and real-time tracking of target region movement, ensuring precise alignment of the radiation beam and minimizing treatment interruptions, while maintaining high dose efficiency and reducing the impact of motion-related image degradation.
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
Implementation Method 2
A treatment system utilizing tomosynthesis to determine target region movement by acquiring and processing projection radiographs in real-time
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 angels, wherein the first processing window slides to the second processing window during treatment of the target region, 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.