Real-Time Tumor Position Estimation via Respiratory Signal Interpolation
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Solution Overview
Problem
Current radiotherapy systems lack a method to estimate internal target position in real-time using a single x-ray imager and external respiratory monitoring sources, which is crucial for effective alignment of radiation beams with targets during treatments like robotic and linear accelerator-based therapies.
Innovation Solution
A methodology that combines x-ray imaging with external respiratory monitoring, utilizing a model to estimate the target position by continuously monitoring respiratory signals and updating parameters with periodic imaging data, optionally incorporating implanted markers to enhance accuracy, while minimizing radiation dosage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If continuous x-ray imaging is used to monitor target position, then measurement precision is improved, but radiation dosage increases
Solution Approach 1:
The system uses periodic x-ray imaging at predetermined time intervals rather than continuous imaging. The imaging device acquires images at specific moments during the treatment cycle, which limits the cumulative radiation exposure while still providing sufficient data points for accurate target position estimation through the model-based approach.
Solution Approach 2:
The system introduces an intermediary modeling approach that combines limited x-ray imaging data with external respiratory monitoring signals. A mathematical model estimates the target position continuously by interpolating between periodic imaging measurements, using respiratory signals as a mediator to bridge the gaps between imaging moments without requiring continuous radiation exposure.
2Device complexity
If a single x-ray imager is used instead of multiple imagers, then device complexity is reduced, but measurement precision deteriorates
Solution Approach 1:
The system performs preliminary actions by acquiring 4D CT or 4D CBCT data before treatment to establish the relationship between external respiratory signals and internal target position. This pre-acquired anatomical and motion information is stored in the model, enabling the single imager to accurately estimate target position during treatment without needing multiple imaging devices.
Solution Approach 2:
The system implements feedback by continuously monitoring external respiratory signals and using them to update the target position estimation in real-time based on the pre-established model. The model parameters are refined using feedback from periodic imaging measurements, creating a closed-loop system that maintains accuracy despite using only a single imager.
3Measurement precision
If imaging frequency is increased to improve position estimation accuracy, then measurement precision is improved, but radiation dosage increases
Solution Approach 1:
The system optimizes the periodicity of imaging to achieve the necessary balance between accuracy and radiation exposure. By carefully selecting the imaging frequency and timing, the system obtains sufficient data for accurate model parameter updates while minimizing the total number of exposures, thereby controlling radiation dosage.
Solution Approach 2:
The system uses partial action by acquiring imaging data at selective moments rather than continuously. The periodic imaging provides just enough data points to maintain model accuracy, avoiding excessive imaging that would increase radiation dosage without providing proportional benefits to measurement 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
This approach allows for accurate and precise real-time estimation of internal target position with reduced radiation exposure, achieving an average root mean square error of 1 mm for tumor motion data, and is applicable to various linear accelerator designs.
Implementation Method 1
imaging of the target using a single imaging device, the imaging being done periodically to limit radiation dosage administered by the single imaging device
Data Source
AI summary
A method and system are disclosed for estimating internal position information of a target in real-time based on a single gantry-mounted x-ray imager and a respiratory signal. The x-ray imaging is done periodically to limit radiation dosage. Initial parameters for the estimation model are determined in a pre-treatment session using four dimensional computed tomography (4D CT) in combination with a respiratory signal acquired from the patient. The model parameters are updated during treatment based on the periodic x-ray image data and the respiratory signal.