Rotary Capacitive Coupler for IVUS Catheter Signal Transmission
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Solution Overview
Problem
Current IVUS catheters face challenges in achieving high axial resolution due to high series inductance and impedance variation in rotary inductive couplers, leading to increased insertion loss and degraded system performance at high frequencies, which limits the ability to visualize micron-sized features like thin-cap fibroatheromas.
Innovation Solution
The implementation of a rotary capacitive coupler, which can include parallel plate, cylindrical surface concentric, or conical surface capacitors, to couple conductors within the catheter, reducing insertion loss and impedance variation, thereby enhancing imaging resolution and maintaining consistent output levels at high frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If rotary inductive couplers are used to couple the stationary ultrasound transceiver to the mechanically rotating transducer, then electrical coupling is achieved, but series inductance increases and impedance varies with rotational position, causing insertion loss and degraded system performance at high frequencies
Solution Approach 1:
The patent changes the electrical coupling parameter from inductive to capacitive. The rotary capacitive coupler uses capacitive elements instead of inductive elements to couple signals between the rotating and stationary components. This parameter change eliminates the frequency-dependent insertion loss and impedance variation problems that plague rotary inductive couplers at high frequencies (30-300 MHz), thereby improving reliability while reducing energy loss.
2Measurement precision
If high frequency operation (30 MHz-300 MHz) is implemented to improve axial resolution, then imaging capability is enhanced, but insertion loss increases with frequency when using rotary inductive couplers
Solution Approach 1:
The patent changes the coupling mechanism parameter from inductive to capacitive to enable high frequency operation. Capacitive coupling has inherently lower loss at high frequencies compared to inductive coupling. This allows the system to operate at 30-300 MHz for improved axial resolution (capable of resolving features smaller than 200 microns) without suffering from the frequency-proportional insertion loss that limits rotary inductive couplers.
3Ease of operation
If rotary inductive couplers are used for electrical coupling, then signal transmission is achieved, but impedance varies with rotational position causing output signal amplitudes to vary with angular positions
Solution Approach 1:
The patent changes the coupling parameter from inductive to capacitive. The rotary capacitive coupler maintains consistent capacitance values regardless of rotational position, unlike inductive couplers whose impedance varies with angle. This parameter change ensures stable impedance matching and consistent output signal amplitudes across all angular positions, improving ease of operation while maintaining impedance stability.
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 rotary capacitive coupler improves axial resolution and system performance by reducing insertion loss and impedance variation, enabling more effective visualization of micron-sized features and vulnerable plaques, such as thin-cap fibroatheromas, at higher transducer frequencies.
Implementation Method 1
The coupler includes a rotary capacitive coupler... a first parallel plate capacitor that couples the first conductor to the third conductor and a second parallel plate capacitor that couples the second conductor to the fourth conductor
Data Source
AI summary
An imaging system comprises a catheter having a lumen, a rotatable imaging probe within the catheter lumen including a distal transducer and first and second conductors coupled to the transducer, and a coupler that couples the rotatable first and second conductors to non-rotatable third and fourth conductors, respectively. The coupler includes a rotary capacitive coupler.