MR-Visible Brachytherapy Markers for Plastic Applicators
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Solution Overview
Problem
Current MRI-guided brachytherapy faces challenges in accurately visualizing and delineating brachytherapy applicators due to the lack of reliable MR-visible markers, leading to inaccuracies and the need for additional radiation exposure with CT imaging.
Innovation Solution
Development of a magnetic resonance visible marker comprising a tube with a proximal and distal end plug and an absorbent thread assembly soaked in an MR-visible fluid, ensuring a fluid-tight seal and minimizing air bubbles for precise imaging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If plastic applicators are used in brachytherapy, then the applicators are biocompatible and flexible, but they do not produce an MR signal and appear as voids in MRI images
Solution Approach 1:
The patent embeds MR-visible markers inside the plastic applicator lumen. The markers are nested within the applicator structure, allowing the applicator to maintain its biocompatible plastic material while containing MR-visible elements that provide imaging contrast. This resolves the contradiction by nesting the functional MR-visible component within the structural plastic applicator.
Solution Approach 2:
The patent uses composite construction by combining plastic applicator material with MR-visible marker materials (such as ferromagnetic substances or materials with different proton density). This creates a hybrid structure where the plastic provides biocompatibility and flexibility, while the embedded MR-visible material provides imaging contrast, thus resolving the visibility contradiction.
2Strength
If titanium applicators are used in brachytherapy, then the applicators provide structural strength, but they create artifacts in MRI images that erroneously localize the applicator
Solution Approach 1:
The patent extracts the MR-visible function from the titanium applicator structure itself and places it into separate, dedicated markers that are inserted into the applicator lumen. This separation allows the titanium to maintain its structural strength while the embedded markers provide accurate MR visibility without the artifacts that would be generated by the titanium itself.
3Measurement precision
If CT images are used to supplement MRI for applicator reconstruction, then applicator visualization is improved, but additional radiation dose is delivered to patients
Solution Approach 1:
The patent replaces the need for CT imaging (which uses ionizing radiation) with an MRI-based system that uses MR-visible markers. The markers provide the necessary contrast for applicator reconstruction entirely within the MRI modality, eliminating the need for supplementary CT scans and thus removing the associated radiation exposure while maintaining reconstruction accuracy.
4Measurement precision
If commercially available MR applicator markers are used, then some applicators can be visualized, but the markers are very large and only suitable for a small subset of applicators
Solution Approach 1:
The patent divides the marker system into small, modular segments that can be inserted into the applicator lumen. These segmented markers are much smaller than commercially available markers and can be accommodated within the narrow lumen of various applicator types, including needles and interstitial applicators, thus greatly expanding versatility while maintaining visualization capability.
5Measurement precision
If commercially available MR markers are filled with liquid media, then the markers become MR-visible, but air bubbles are trapped in the marker line resulting in incorrect applicator reconstruction
Solution Approach 1:
The patent employs a porous absorbent material within the marker structure that can absorb and retain the liquid media. This porous structure allows the liquid to be evenly distributed and retained within the marker without trapping air bubbles, as the capillary action in the porous material draws the liquid in uniformly, eliminating the air bubble problem while maintaining MR visibility.
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
The MR-visible marker provides accurate and reproducible reconstruction of brachytherapy applicators, enhancing imaging clarity and reducing the need for additional radiation exposure by using MR alone.
Implementation Method 1
an absorbent thread assembly which has been soaked in and thereby absorbed a magnetic resonance visible fluid
Data Source
AI summary
Magnetic resonance (“MR”) visible markers for use in MR-guided placement of brachytherapy seeds, and for use in other MR-guided interventional procedures, are described. The MR-visible markers generally include a tube in which an absorbent thread assembly is disposed. The tube is made fluid-tight by sealing it at both ends with suitable end plugs. The absorbent thread assembly is soaked in a suitable MR-visible fluid.