Target Position Determination Using 4D CT Data and Single X-Ray Imaging
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Solution Overview
Problem
In radiotherapy, existing systems struggle to accurately determine the position of a target within a patient's body when one X-ray imaging source is blocked, such as by a gantry, leading to potential misses in irradiation due to the inability to calculate correct 3D coordinates.
Innovation Solution
A data processing method that utilizes a target movement model, acquired from prior measurements, to determine the 3D position of a target even when only one imager has a clear view, by combining the single 2D update signal with the target movement model and stereoscopic imaging principles, allowing for positional constraint information to rule out invalid positions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If stereoscopic imaging from two X-ray sources is used to determine target position, then measurement precision is improved, but device complexity and operational requirements increase
Solution Approach 1:
The system performs preliminary actions by acquiring a 4D CT dataset before treatment, which pre-calculates and stores projection images of the target at multiple phases of the respiratory cycle. This preliminary data preparation enables the system to determine target position during treatment without requiring complex real-time stereoscopic imaging, thus reducing device complexity while maintaining measurement precision.
Solution Approach 2:
The invention uses copied data from the 4D CT scan by matching 2D projection images acquired during treatment with pre-acquired projection images from the 4D CT dataset. This copying approach allows the system to determine target position without requiring a second live X-ray source, thereby reducing device complexity while preserving measurement accuracy through image matching algorithms.
2Reliability
If two X-ray imaging sources are required for clear line of sight, then target position determination reliability is improved, but ease of operation deteriorates
Solution Approach 1:
The system performs preliminary acquisition of comprehensive 4D CT data that includes target position information at multiple respiratory phases. This pre-acquired data serves as a reference library that can be queried during treatment without requiring complex real-time imaging from multiple sources, thus maintaining reliability while simplifying operation.
Solution Approach 2:
The invention introduces an intermediary approach by using 2D projection image matching as a mediator between the single X-ray source and the 3D target position determination. The image matching algorithm acts as an intermediary that translates limited 2D information into accurate 3D position data, eliminating the need for complex multi-source imaging while maintaining reliability.
3Measurement precision
If system repositioning is performed to maintain clear line of sight, then measurement precision is maintained, but loss of time increases
Solution Approach 1:
The system performs preliminary acquisition of 4D CT data that captures target position information across the full range of motion. This pre-acquired comprehensive dataset eliminates the need for time-consuming system repositioning during treatment, as the system can continuously reference the pre-acquired data to maintain measurement precision without interrupting the treatment workflow.
4Reliability
If continuous stereoscopic imaging is performed, then target position monitoring reliability is improved, but use of energy and radiation exposure increase
Solution Approach 1:
The system uses periodic action by acquiring 4D CT data at multiple discrete phases of the respiratory cycle rather than continuous imaging. During treatment, it periodically updates target position by matching 2D projection images with the pre-acquired 4D CT data, maintaining monitoring reliability while significantly reducing radiation exposure compared to continuous stereoscopic imaging.
Data Source
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AI summary
A data processing method for determining the position of a target, comprising the steps performed by a computer: a) acquiring a target movement model specifying a movement cycle of the target; b) acquiring a target position signal representing a view of the target from a single direction and/or provided by a single imager; c) determining, based on the acquired target position signal and the target movement model, the position of the target.