MR-Safe RF Cable Fuse Segmentation for Heating Prevention
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Solution Overview
Problem
Resonant RF common mode currents induced by MR imaging apparatuses cause severe heating in interventional and non-interventional instruments, such as catheters and guide wires, due to their interaction with electromagnetic RF excitation fields, which existing solutions like MR-safe transmission lines fail to adequately address, as they are complex, bulky, and not always reliable.
Innovation Solution
Incorporating a plurality of fuses into the RF transmission line or cable, where each fuse is spaced at a quarter of the effective wavelength of the induced RF common mode current or less, and designed to become non-conducting when the current or temperature exceeds a preset threshold, effectively preventing heating by interrupting the current flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If MR-safe transmission lines are used to prevent heating, then patient safety is improved, but device complexity and bulk increase
Solution Approach 1:
The transmission line is segmented by inserting fuses at specific intervals (quarter-wavelength or less) along its length. This segmentation disrupts the resonant RF common mode currents that cause heating, while maintaining a relatively simple overall structure. The fuses create multiple discontinuities that prevent standing wave formation without requiring complete redesign of the transmission line.
Solution Approach 2:
The patent employs fuses as disposable protective elements that can be easily replaced. These fuses are simple, inexpensive components compared to complex MR-safe transmission lines. When a fuse blows due to excessive current, it provides protection against heating, and the simple replacement process minimizes downtime and cost.
2Object-affected harmful factors
If complex MR-safe transmission lines are used to suppress standing waves, then heating is reduced, but ease of manufacture decreases
Solution Approach 1:
Rather than manufacturing a completely complex MR-safe transmission line, the patent segments a standard transmission line by adding discrete fuse elements at specific intervals. This approach is much easier to manufacture than designing and building an entirely new MR-safe line, as it uses simple modifications to existing components.
Solution Approach 2:
The patent changes the electrical parameters of the transmission line by adding fuses at quarter-wavelength intervals. This parameter modification (adding discrete impedance discontinuities) is a simple manufacturing change that achieves the desired effect of suppressing standing waves without requiring complex manufacturing processes.
3Object-affected harmful factors
If fuses are placed close together to prevent heating, then heating prevention is improved, but device complexity increases
Solution Approach 1:
The fuse arrangement serves multiple functions: it suppresses standing waves, prevents overheating, and maintains broadband signal transmission capability. By positioning fuses at quarter-wavelength intervals, a single structural feature achieves multiple protective functions without requiring additional complex components or arrangements.
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 provides reliable and cost-effective MR safety by preventing heating in instruments and cables, allowing for broadband signal transmission without the need for complex or bulky components, and can be integrated into instruments with small cross-sections like catheters, ensuring patient safety.
Implementation Method 1
each fuse is selected such that it turns into an at least substantially non-conducting state when the current flowing through the fuse or the temperature of the fuse due to the current flowing through the fuse reaches or exceeds a preset threshold value
Implementation Method 2
each fuse is selected such that it turns into an at least substantially non-conducting state when the current flowing through the fuse or the temperature of the fuse due to the current flowing through the fuse reaches or exceeds a preset threshold value
Implementation Method 3
resonant RF common mode currents which are induced in the RF transmission line or cable by the RF excitation field
Implementation Method 4
resonant RF common mode currents which are induced in the RF transmission line or cable by the RF excitation field
Data Source
Figure 1~3
AI summary
An interventional or a non-interventional instrument like a catheter, a surgical device, a biopsy needle, a pointer, a stent or another invasive or non-invasive device, like a position marker, or a surface or local coil like a head coil is disclosed, wherein these instruments are provided with an MR-safe RF transmission line or cable (2, 3) for connecting the instrument with related RF transmit/MR receive units or other signal processing units for operating the instrument during an MR imaging or MR examination of an examination object. Basically, MR safety is obtained or increased by means of a plurality of fuses (6) which are serially connected into the transmission line or cable (2, 3).