EPID Isocenter Verification via Dose Profile Inflection Points
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current EPID-based methods for verifying and correcting the isocenter of radiotherapy devices face challenges such as lower resolution capacity, inability to perform measurements with certain support arm and couch angle combinations, unfavorable signal/noise ratio, unsuitability for MLC-shaped irradiation fields, and lack of representation of the global isocentroid, leading to inaccuracies in central beam deviation determination.
Innovation Solution
A method involving positioning a measurement body at the radiological isocenter, capturing dose images, determining inflection points in dose profiles, linking these points to bodily and field limits, calculating differential vectors to correct the isocenter, and using coordinate transformations to account for machine tolerances, allowing for precise verification and correction of the isocenter with existing EPID systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If EPID-based methods are used for isocenter verification, then the measurement process can be performed with existing radiotherapy devices, but the resolution capacity is lower compared to film-based methods
Solution Approach 1:
The patent segments the dose image into multiple profiles (first dose profile and second dose profile) along different directions. By analyzing inflection points in these segmented profiles rather than the entire image at once, the method achieves higher measurement precision with EPID systems that have inherently lower resolution compared to film-based methods.
Solution Approach 2:
The patent transforms the two-dimensional dose image into one-dimensional dose profiles by extracting specific lines through inflection point analysis. This dimensional reduction allows for more precise measurements in specific directions, compensating for the lower overall resolution capacity of EPID systems.
2Productivity
If traditional EPID-based methods are used, then isocenter verification can be performed, but certain support arm and couch angle combinations cannot be measured
Solution Approach 1:
The patent creates a universal verification method that works across multiple angle combinations by determining inflection points in dose profiles rather than relying on specific geometric configurations. The method can handle various support arm angles and couch angles, making it adaptable to different measurement scenarios that traditional methods cannot accommodate.
3Ease of manufacture
If EPID-based methods are used, then the measurement can be performed with existing devices, but the signal/noise ratio is unfavorable
Solution Approach 1:
The patent extracts specific information (inflection points) from the dose images rather than using the entire image data. By focusing only on the critical inflection points that indicate isocenter position, the method improves the signal-to-noise ratio by eliminating irrelevant background information that would otherwise degrade the measurement reliability.
4Productivity
If conventional EPID methods are used, then isocenter verification is possible, but MLC-shaped irradiation fields cannot be properly evaluated
Solution Approach 1:
The patent develops a universal evaluation method based on inflection point detection that works with any irradiation field shape, including MLC-shaped fields. Unlike traditional methods that assume specific field geometries, this approach identifies isocenter position through directional dose profiles, making it compatible with complex MLC field shapes while maintaining verification capability.
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 method achieves a spatial resolution of 0.01 mm for central beam deviation, enabling accurate isocenter verification and correction without the need for technical modifications to existing radiation therapy devices, thereby enhancing patient safety and reducing costs by allowing for immediate verification prior to radiosurgical applications.
Implementation Method 1
a digital recording system (EPID—electronic portal imaging device) for acquiring dose images by means of the therapy beam
Data Source
AI summary
A method for EPID-based verification, correction and minimization of the isocenter of a radiotherapy device includes the following: Positioning a measurement body; applying an irradiation field; capturing a common dose image of the measurement body; creating a dose profile on the basis of the captured dose image; determining an inflection point in a plot of the dose profile; linking positions of the inflection points to bodily limits of the measurement body; determining position of a center point of the measurement body relative to an EPID-center; determining a differential vector from a deviation in position of the center point of the measurement body from the EPID-center and from a deviation in position of the field center point of the irradiation field from the EPID-center; and correcting the current radiological isocenter.