Radiotherapy Gantry Alignment Monitoring via Static MRI Features
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Solution Overview
Problem
Current radiotherapy systems face challenges in maintaining accurate beam alignment due to movement of components on a rotatable gantry, particularly in integrated MRI-linear accelerator systems, where repeated use of phantoms for calibration is impractical and alignment errors can occur during normal operation.
Innovation Solution
A method involving obtaining reference and subsequent images using a radiotherapy imaging system to determine changes in the relative positions of system components, with static features of the MRI system serving as spatial references to identify potential misalignments, allowing for correction of gantry rotation and maintaining precise beam alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a phantom is used for calibration to ensure accurate beam alignment, then alignment precision is improved, but the time required for calibration increases and repeated use becomes impractical
Solution Approach 1:
The patent uses a digital copy (image) of the static component instead of the physical phantom for repeated calibration checks. The reference image serves as a virtual template that can be compared against subsequent images without requiring physical phantom placement or removal, enabling rapid repeated verification of alignment accuracy.
Solution Approach 2:
The system uses its own imaging capability to perform self-alignment verification. By capturing images of the static component and comparing them against a reference image, the system automatically detects alignment deviations without requiring external calibration equipment or manual intervention, thus eliminating calibration time while maintaining precision.
2Adaptability or versatility
If the gantry is rotated to deliver radiation from multiple directions, then treatment effectiveness is improved, but alignment errors may be introduced between rotations
Solution Approach 1:
The patent implements a feedback mechanism where images of the static component are captured at different gantry angles and compared against a reference image. Any positional deviations detected through image comparison provide feedback about alignment errors, which can then be corrected to maintain reliable beam positioning across multiple gantry rotations.
Solution Approach 2:
The system performs preliminary alignment verification by capturing and analyzing images of the static component before delivering radiation beams. This preliminary check ensures that the gantry is properly positioned and aligned, preventing alignment errors from propagating into the treatment delivery process.
3Measurement precision
If static components are used as reference markers, then alignment monitoring capability is improved, but the complexity of the system increases
Solution Approach 1:
The static component serves multiple functions: it acts as both a structural element of the MRI system and as a reference marker for alignment monitoring. By making the reference marker an integral part of the existing system rather than a separate component, the patent avoids increasing overall system complexity while still providing robust alignment monitoring capability.
Data Source
AI summary
A method of operating a radiotherapy system mounted on a gantry surrounding a magnetic resonance imaging system is provided, the radiotherapy system comprising a radiotherapy beam generator, and a radiotherapy imaging system, wherein the gantry is arranged to rotate the radiotherapy beam generator around the magnetic resonance imaging system. The method comprises obtaining a reference image, the reference image including a predetermined feature of the magnetic resonance imaging system located near the radiotherapy imaging system; rotating the gantry relative the magnetic resonance imaging system; obtaining a second image, the second image including the predetermined feature of the magnetic resonance imaging system located near the radiotherapy imaging system; and determining changes in the relative positions of the radiotherapy beam generator, the radiotherapy imaging system, and the magnetic resonance imaging system based on differences in the position of the predetermined feature in the reference image and in the further image.