Absorbing device for radiotherapy
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Solution Overview
Problem
Existing electromagnetic target localization systems in radiotherapy face accuracy issues due to interaction with conductive materials in the treatment table and gantry, leading to localisation errors and reduced communication distance between wireless transponders and transceivers, which are not effectively addressed by current solutions.
Innovation Solution
An absorbing device with layers of high magnetic permeability and low surface conductivity materials, such as ferrite sheets, is positioned between the patient and the conductive treatment table to absorb electromagnetic fields, preventing interaction and minimizing eddy currents, while maintaining X-ray transparency and avoiding radiation artifacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional carbon-fibre couch top is used, then X-ray transparency and dose dosimetry are optimized, but electromagnetic fields from the localisation system interact with the conductive material causing localisation errors
Solution Approach 1:
An electromagnetic absorbing layer is introduced as an intermediary between the patient and the conductive treatment table. This layer absorbs electromagnetic fields generated by the localisation system, preventing them from interacting with the conductive carbon-fibre couch top. The absorbing layer is positioned directly on the couch top surface, creating a non-conductive barrier that eliminates eddy currents while maintaining X-ray transparency for imaging and treatment monitoring.
Solution Approach 2:
The electromagnetic properties of the couch top surface are modified by adding an absorbing layer with specific electromagnetic absorption characteristics. This layer changes the surface impedance and electromagnetic response, converting the conductive surface into an effectively non-conductive surface for electromagnetic frequencies while maintaining mechanical support functions. The layer thickness and material composition are optimized to achieve the desired electromagnetic absorption without compromising X-ray transmission.
2Object-affected harmful factors
If a non-standard carbon couch top with special fibre routing is used, then electromagnetic interaction is reduced, but manufacturing complexity and cost increase significantly
Solution Approach 1:
The solution separates the electromagnetic absorption function from the structural support function of the couch top. Instead of modifying the entire carbon-fibre couch top construction with complex fibre routing patterns, the electromagnetic absorption is achieved through a separate, removable absorbing layer that sits on top of the conventional couch top. This segmentation allows the couch top to maintain its simple, cost-effective manufacturing while the absorbing layer handles the electromagnetic interference mitigation.
Solution Approach 2:
The couch top system becomes a composite structure combining the conventional carbon-fibre couch top with an electromagnetic absorbing material layer. This composite approach allows each component to maintain its original manufacturing simplicity while gaining additional functionality. The absorbing layer can be made from cost-effective materials such as ferrite or other electromagnetic absorbing compounds, avoiding the need for expensive custom carbon-fibre weaving patterns.
3Measurement precision
If the absorbing layer is made with high electromagnetic absorption properties, then localisation accuracy improves, but X-ray artifacts and radiation dose changes may occur
Solution Approach 1:
The thickness and material composition of the absorbing layer are optimized to achieve the desired electromagnetic absorption while minimizing X-ray interaction. By carefully controlling the layer thickness (typically thin films or coatings) and selecting materials with appropriate atomic numbers and densities, the layer provides sufficient electromagnetic absorption for accurate localisation while remaining sufficiently transparent to X-rays for imaging and treatment monitoring without creating significant artifacts or dose perturbations.
Solution Approach 2:
The absorbing layer is positioned specifically where electromagnetic absorption is most needed - directly on the couch top surface beneath the patient - rather than throughout the entire treatment system. This localized application ensures that electromagnetic absorption occurs precisely where the conductive couch top would otherwise cause interference, while minimizing the total amount of material in the X-ray path. The layer can be applied only in specific zones rather than uniformly across the entire couch top surface.
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 solution ensures accurate target localization and extended communication distance between transponders and transceivers, allowing for precise radiotherapy treatment without introducing radiation artifacts or altering dose dosimetry, and is compatible with conventional carbon-fibre couch tops.
Implementation Method 1
at least one layer of an electromagnetic radiation absorbing material, wherein the absorbing material is for preventing interaction between a target localisation system having a targeted frequency range of between about 300kHz and about 500kHz and a conductive treatment table
Implementation Method 2
An absorbing device with layers of high magnetic permeability and low surface conductivity materials, such as ferrite sheets, is positioned between the patient and the conductive treatment table to absorb electromagnetic fields, preventing interaction and minimizing eddy currents
Implementation Method 3
part of the alternating magnetic energy is transferred to circular current on the surface of the conductive materials and is eventually dissipated as heat
Data Source
Figure 1
Figure 2a~2b
Figure 3
AI summary
An absorbing device (24, 24', 24", 41) for radiotherapy treatment comprising at least one layer of electromagnetic absorbing material wherein the absorbing material is for preventing interaction between a target localisation system (1) having a targeted frequency range of between about 300kHz and 500kHz and a treatment table (4).