Treatment Planning System for Dynamic Dose Calculation
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Solution Overview
Problem
Current radiation therapy treatment planning systems face challenges in accurately calculating dose distribution due to tumor movements caused by respiration and heartbeat, especially when irradiation parameters such as gantry angle, beam position, and intensity vary over time, leading to potential irregularities in dose distribution.
Innovation Solution
A treatment planning system that uses 4D CT images to interpolate variations in the target region over time, associating tumor movements with irradiation parameters to improve the accuracy of dose distribution calculations by generating a 3D image reflecting the target region's state at any given time during radiation therapy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional treatment planning systems calculate dose distribution based on static CT images, then the calculation process is simple and fast, but the accuracy of dose distribution is compromised due to tumor movements caused by respiration and heartbeat
Solution Approach 1:
The patent applies dynamics by transitioning from static CT images to 4D CT images that capture temporal variations in target region position and shape. The system dynamically updates the target region geometry across multiple time phases (e.g., respiratory cycles) to reflect actual tumor movements during irradiation, thereby improving dose distribution accuracy while managing computational complexity through phase-based segmentation
Solution Approach 2:
The patent segments the continuous temporal variation of target region into discrete time phases using 4D CT imaging. Each phase represents a specific moment in the respiratory or cardiac cycle, allowing the system to calculate dose distribution for each segmented phase separately and then integrate the results. This segmentation approach makes the complex dynamic problem tractable by breaking it into manageable static calculations
2Measurement precision
If the system uses 4D CT images to account for tumor movements, then the dose distribution accuracy improves, but the calculation time and computational load increase significantly
Solution Approach 1:
The patent performs preliminary action by pre-calculating and storing the temporal variations of target region position and shape from 4D CT images before the actual treatment planning. The system prepares phase-separated target geometry data in advance, so that during dose calculation, it only needs to retrieve and integrate pre-processed temporal variations rather than performing full dynamic simulations from scratch, thereby reducing treatment planning time
Solution Approach 2:
The patent exploits the periodic nature of respiratory and cardiac cycles by dividing the 4D CT data into repeating phases. The system calculates dose distribution for representative phases and integrates them using weight factors that reflect the temporal distribution of each phase within the cycle. This periodic approach reduces computational load compared to continuous time-dependent calculations
3Adaptability or versatility
If irradiation parameters such as gantry angle and beam intensity vary over time, then the treatment plan can adapt to tumor movements, but the dose distribution becomes more difficult to predict and control
Solution Approach 1:
The patent adds the time dimension to the traditional three-dimensional dose calculation by incorporating temporal variations of target region from 4D CT images. The system extends the dose integration process to four dimensions (three spatial dimensions plus time), allowing it to account for both spatial irradiation parameter variations and temporal target movements simultaneously. This dimensional extension enables the system to predict and control dose distribution in dynamically varying conditions
Data Source
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AI summary
A treatment planning system is provided which, with irradiation parameters varied over time, performs highly accurate dose distribution calculations based on information about tumor movements included in 4D CT images. The system is characterized by the ability to read CT images furnished with timing information and associate the status of the irradiation target corresponding to an elapsed time from the beginning of irradiation with positions being irradiated at corresponding elapsed time points so as to calculate the dose distribution.