Tumor Position Tracking via Image Registration
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Solution Overview
Problem
Current methods for detecting the position of a moving object, such as a tumor, within a body during respiratory motion are inadequate as they fail to accurately account for internal displacements caused by breathing or pulsation, especially when external markers alone are used, leading to potential radiation exposure of healthy tissue due to enlarged target volumes.
Innovation Solution
The method employs digital tomosynthesis and cone-beam computed tomography to register and reconstruct images of the object's position, correlating image acquisition angles and respiratory states to determine the object's 3D shape and movement, allowing for precise tracking without the need for continuous 4D CT scans, and uses intensity-based registration to compensate for small deviations, thereby updating the tumor's trajectory accurately.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If external markers are used to track respiratory motion, then the tracking speed and ease of operation are improved, but the measurement precision of internal object position deteriorates because external markers cannot adequately reflect internal displacements
Solution Approach 1:
The patent introduces image-based intermediaries (2D radiographic images and 3D scan data) that serve as a bridge between external markers and internal objects. The registration process matches external marker positions with internal object positions in the images, allowing indirect tracking of internal objects while maintaining the ease of external marker placement.
Solution Approach 2:
The patent creates a virtual copy of the internal object's position and motion trajectory through image registration. By matching 2D radiographic images with 3D scan data, the system reconstructs the internal object's position without directly observing it, effectively copying its motion pattern from the registered image data.
2Measurement precision
If continuous 4D CT scans are performed to track tumor position, then the measurement precision is improved, but the radiation exposure and use of energy increase significantly
Solution Approach 1:
The patent replaces continuous 4D CT scanning with periodic 2D radiographic imaging. Instead of continuously acquiring volumetric data, the system takes individual 2D images at specific moments and registers them with pre-acquired 3D scan data, dramatically reducing radiation exposure while maintaining the ability to track tumor position throughout the respiratory cycle.
Solution Approach 2:
The patent performs preliminary registration between 2D radiographic images and 3D scan data before treatment. This pre-registration creates a mapping relationship that allows the system to determine tumor position from routine 2D images during treatment without requiring additional 4D CT scans, thereby reducing radiation exposure during the actual treatment process.
3Reliability
If target volume is enlarged to account for respiratory motion, then the reliability of treatment is improved by ensuring tumor coverage, but the harmful factors increase due to radiation exposure of healthy tissue
Solution Approach 1:
The patent transitions from static target volume definition to dynamic tracking. By continuously monitoring external marker positions and using registered image data to determine internal object position throughout the respiratory cycle, the system can dynamically adjust the radiation beam to follow the moving tumor, eliminating the need for static volume enlargement and thereby protecting healthy tissue.
Solution Approach 2:
The patent implements a feedback loop where external marker positions are continuously monitored, correlated with registered image data to determine internal object position, and used to adjust radiation delivery in real-time. This feedback mechanism ensures accurate tumor targeting without requiring excessive safety margins, thus reducing radiation exposure to surrounding healthy tissue.
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 precise tracking of the tumor's position and movement, reducing the need for continuous radiation exposure and minimizing the impact on healthy tissue by accurately determining the object's position and trajectory, allowing for more targeted radiation therapy.
Implementation Method 1
An x-ray source being positioned on one side of the patient emits x-rays in the direction of an x-ray detector positioned on the opposing side to obtain 2D images of a region of interest of the patient
Implementation Method 2
The markers can be tracked automatically with known optical methods at a high speed to obtain a position signal, which can for example be a breathing signal or a pulsation signal
Data Source
AI summary
The invention relates to a method for determining the position of an object moving within a body, wherein the body is connected to markers, a movement signal is determined based on the measured movement of the markers, images are taken from the object using a camera or detector, wherein the camera or detector is moved with respect to the object, it is determined from which direction or range of angles or segment the most images corresponding to a predefined cycle of the movement signal are taken, and using at least some or all of the images of the segment containing the most images for a specified movement cycle, an image of the object is reconstructed.