Calibration Phantom for MRI-Linac Coordinate Registration
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Solution Overview
Problem
Current calibration methods for integrating MRI and radiotherapy systems are prone to errors due to the replacement of ball bearings with MR imaging markers and the translation of phantoms between imaging systems, leading to inaccuracies in coordinate registration.
Innovation Solution
A phantom comprising two coupled components with tapered elongate members and reservoirs for holding liquid, allowing for accurate center determination using both MRI and radiographic imaging modalities, with markers made from non-magnetic, high-density materials like zirconia for x-ray visibility and ceramics for MRI compatibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If ball bearings are replaced with MR imaging markers to enable MRI imaging, then the phantom becomes compatible with MRI systems, but positioning accuracy deteriorates due to potential misalignment between markers and original ball bearing locations
Solution Approach 1:
A non-magnetic, radiopaque intermediary material (such as titanium or ceramic beads) is introduced as a mediator that is compatible with both MRI and radiographic imaging systems. This intermediary marker maintains the exact position of the original ball bearing while being visible in both imaging modalities, thereby resolving the conflict between MRI compatibility and positioning accuracy.
2Adaptability or versatility
If the phantom is translated between imaging systems for calibration, then calibration between different systems is enabled, but positioning accuracy deteriorates due to translation errors
Solution Approach 1:
The patent merges the calibration capabilities for both MRI and radiographic systems into a single integrated phantom design. The phantom includes features that are simultaneously visible in both imaging modalities, eliminating the need to physically translate the phantom between systems and thereby maintaining positioning accuracy while enabling system integration.
3Adaptability or versatility
If different marker materials are used for x-ray and MRI imaging, then visibility in both modalities is achieved, but system integration complexity increases
Solution Approach 1:
The patent employs composite marker materials that combine properties for both x-ray radiopacity and MRI compatibility. Examples include titanium-based composites or ceramic materials that provide high radiographic visibility while being non-magnetic and MRI-safe, thereby achieving multimodality compatibility without increasing design complexity.
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
Enables precise calibration of MRI-Linac systems by accurately determining the centers of pockets in both imaging modalities, ensuring reliable coordinate registration and minimizing errors in therapeutic beam targeting.
Implementation Method 1
magnetic resonance imaging (MRI) system
Implementation Method 2
x-ray visibility and ceramics for MRI compatibility
Data Source
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AI summary
Embodiments of the present invention provide phantoms, and associated methods of calibration which are suitable for use in both medical resonance imaging and radiographic imaging systems. A phantom for calibration of a medical imaging system, comprises a first component having a first outer shape, a portion of which defines part of at least one pocket; and a second component coupled to the first component and having a second outer shape, a portion of which defines another part of the at least one pocket. At least one of the first and second components comprises a reservoir, the reservoir having a shape at least a portion of which locates a centre of the at least one pocket.