EM-Compatible Stepper for Brachytherapy Tracking Accuracy
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Solution Overview
Problem
Commercially available brachytherapy steppers with significant metal content cause distortions in electromagnetic tracking data due to ferromagnetic and non-ferrous metals, leading to inaccuracies in guidance and navigation during procedures like transrectal ultrasound-guided brachytherapy.
Innovation Solution
An interventional tool stepper with components made from electromagnetic-compatible materials such as biomedically compliant plastics and non-ferrous metals, designed to minimize electromagnetic field distortions, including a frame, carriage, and grid template, which can be configured to hold and translate/rotate a transrectal ultrasound probe and guide needle/catheter insertion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If metallic components are used in the stepper for structural strength and durability, then mechanical strength and stability are improved, but electromagnetic field distortion increases causing tracking inaccuracies
Solution Approach 1:
The patent changes the material parameters of the stepper components from ferromagnetic and conductive metals to non-ferromagnetic, electrically non-conductive materials such as polymers (e.g., polyetheretherketone or polyarylethersulfone). This parameter change eliminates the generation of eddy currents and magnetic distortions while maintaining structural integrity through careful material and structural design
Solution Approach 2:
The patent employs composite material construction for the stepper components, combining non-ferromagnetic polymer matrices with embedded non-conductive reinforcement structures. These composite materials provide the necessary mechanical strength and stability while maintaining electromagnetic compatibility, as they do not generate eddy currents or magnetic field distortions
2Stability of the object's composition
If ferromagnetic metals are used in the stepper, then structural stability is improved, but spatial distortion of the electromagnetic field increases
Solution Approach 1:
The patent changes the magnetic properties of the stepper materials from ferromagnetic to non-ferromagnetic by using polymers and non-ferromagnetic composites. This parameter change eliminates magnetic field distortion and spatial inaccuracies in EM tracking while structural stability is maintained through optimized mechanical design and material selection
3Ease of manufacture
If non-ferrous metals are used in the stepper, then ease of manufacture is improved, but eddy current generation increases causing tracking errors
Solution Approach 1:
The patent changes the electrical conductivity parameter of the stepper materials from conductive (non-ferrous metals) to non-conductive (polymers and non-conductive composites). This parameter change eliminates eddy current generation and associated tracking errors. The manufacturing process is adapted to work with these materials, using techniques such as injection molding and composite fabrication
Solution Approach 2:
The patent uses non-conductive composite materials that combine polymer matrices with non-conductive reinforcement structures. These composites provide the necessary mechanical properties while maintaining electrical non-conductivity, preventing eddy current generation. The composite structure can be manufactured using modern composite fabrication techniques
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 EM-compatible stepper reduces electromagnetic field distortions to levels comparable to inherent noise in tracking technology, ensuring accurate guidance and navigation by minimizing eddy currents and spatial distortions, thereby enhancing treatment efficacy.
Implementation Method 1
ferromagnetic metals as well as eddy currents generated by non-ferrous metals (e.g., aluminum) have the largest impact on spatial distortions of the EM field
Implementation Method 2
metallic equipment in the vicinity of the field of view ('FOV') of an EM field generator may cause distortions in the tracking
Data Source
AI summary
An interventional tool stepper (30) employing a frame (31), a carriage (33), an optional gear assembly (32), and an optional grid template(34). The frame (31) is structurally configured to be positioned relative to an anatomical region for holding an interventional tool (40) relative to the anatomical region. The carriage (33) is structurally configured to hold the interventional tool (40) relative to the anatomical region. The gear assembly (32) is structurally configured to translate and/or rotate the carriage (33) relative to the frame (31). The grid template (34) is structurally configured to guide one or more additional interventional tools (41) relative to the anatomical region. The frame (31), the carriage (33), the optional gear assembly (32) and the optional grid template (34) have an electromagnetic-compatible material composition for minimizing any distortion by the interventional tool stepper (30) of an electromagnetic field.