Radiotherapy Test Object Using Nested Spheres for Isocenter Alignment
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Solution Overview
Problem
Current test objects for radiotherapy treatment apparatus quality control face inaccuracies in placing a radiopaque ball at the intersection of laser layers and fail to verify the orthogonality, coincidence, and spatial position of the three theoretical axes, leading to potential misalignment between theoretical and real isocenters, which can result in incomplete tumor irradiation and irradiation of healthy tissues.
Innovation Solution
A test object comprising a spherical ball of high electron density placed at the center of a larger sphere with lower electron density, where the ball's diameter is smaller than the radiation beam and the sphere's diameter is greater, allowing precise alignment using visual alignment means on the sphere's surface, facilitating accurate placement and detection of the ball's position relative to the theoretical axes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a radiopaque ball is used as a test object, then the ball can be detected in X-ray images, but the ball cannot be precisely aligned with the laser layers due to its small size
Solution Approach 1:
The patent embeds a small radiopaque ball (10-20mm diameter) inside a larger transparent sphere (50-100mm diameter). The outer sphere acts as a container that holds the inner ball, allowing the combination to be aligned with laser layers using the larger outer surface, while the inner ball remains detectable in X-ray images for isocenter verification.
Solution Approach 2:
The outer sphere is made transparent or translucent to visible light, allowing laser alignment marks to be clearly seen through it. This optical property enables precise visual alignment with laser layers during setup, while the radiopaque inner ball provides contrast in X-ray images for detection.
2Measurement precision
If the radiopaque ball diameter is reduced to improve alignment precision, then alignment accuracy improves, but the ball becomes harder to detect in X-ray images
Solution Approach 1:
The patent embeds a small radiopaque ball (10-20mm diameter) inside a larger transparent sphere (50-100mm diameter). The outer sphere acts as a container that holds the inner ball, allowing the combination to be aligned with laser layers using the larger outer surface, while the inner ball remains detectable in X-ray images for isocenter verification.
3Manufacturing precision
If a small radiopaque ball is used, then the ball fits within the radiation beam section, but the ball cannot serve as an alignment reference with laser layers
Solution Approach 1:
The patent embeds a small radiopaque ball (10-20mm diameter) inside a larger transparent sphere (50-100mm diameter). The outer sphere acts as a container that holds the inner ball, allowing the combination to be aligned with laser layers using the larger outer surface, while the inner ball remains detectable in X-ray images for isocenter verification.
Solution Approach 2:
The outer sphere is made transparent or translucent to visible light, allowing laser alignment marks to be clearly seen through it. This optical property enables precise visual alignment with laser layers during setup, while the radiopaque inner ball provides contrast in X-ray images for detection.
4Loss of information
If the radiopaque ball diameter is increased to improve detection, then detection ease improves, but the ball extends beyond the radiation beam section
Solution Approach 1:
The patent embeds a small radiopaque ball (10-20mm diameter) inside a larger transparent sphere (50-100mm diameter). The outer sphere acts as a container that holds the inner ball, allowing the combination to be aligned with laser layers using the larger outer surface, while the inner ball remains detectable in X-ray images for isocenter verification.
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 configuration enables precise alignment and detection of the ball's position, improving the accuracy of isocenter alignment and orthogonality verification, reducing the risk of misalignment and enhancing the precision of radiation targeting during radiotherapy.
Implementation Method 1
a spherical ball made of a material having an electron density d1, and placed at the center of a sphere made of a material having an electron density d2
Implementation Method 2
take multiple X-rays of this object with the X-rays from treatment beams
Data Source
Figure 1~2
Figure 3
Figure 4~5
AI summary
The object has a spherical ball (9) placed at center of filled sphere (8) to form a test-object. The ball and the sphere have diameters respectively ranging between 5 and 6 mm, and 80 and 200 mm and formed from materials with electronic densities whose ratio is greater than or equal to 1.1. The sphere carries a visual alignment unit formed by visible equatorial lines, orthogonal in pairs, on outer surface to allow positioning of the object. The sphere has thread securing positioning units formed of a metal rod (13) and a plate (14) of the object on radiotherapy treatment apparatus. Independent claims are also included for the following: (1) a method for manufacturing a test-object (2) a method for verifying coincidence, orthogonality and position in a space of treatment room of marking unit of isocenter of radiotherapy treatment apparatus (3) a method for searching isocenter of radiotheraphy treatment apparatus by using test object.