Shield-Coupling Capacitor for Intravascular Ultrasound Noise and Leakage Control
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Solution Overview
Problem
Intravascular ultrasound (IVUS) imaging systems face challenges in reducing electrical noise while ensuring patient safety from leakage currents, particularly when using conductive shields coupled to system ground, as this can lead to potentially harmful leakage currents during fault conditions.
Innovation Solution
The implementation of a shield-coupling capacitor with rotating capacitors, which includes both rotating and stationary plates, is used to couple the conductive shield to a system ground, providing a low impedance path for radio-frequency currents and maintaining high-voltage isolation, thereby reducing electrical noise and limiting patient leakage current exposure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a conductive shield is coupled to system ground, then electrical noise is reduced, but patient leakage current exposure increases
Solution Approach 1:
A capacitive coupling mechanism is introduced as an intermediary between the conductive shield and system ground. The capacitor allows RF signals to pass through for noise reduction while blocking DC leakage currents from reaching the patient, thus resolving the contradiction between electrical noise reduction and leakage current safety
2Object-generated harmful factors
If a shield-coupling capacitor is used, then leakage current is limited, but electrical noise reduction effectiveness decreases
Solution Approach 1:
The capacitor value is carefully selected and adjusted to optimize the frequency-dependent impedance characteristics. By changing the capacitance parameter, the system achieves low impedance at RF frequencies for noise reduction while maintaining high impedance at DC for leakage current blocking, thus resolving the contradiction between limiting leakage current and maintaining noise reduction effectiveness
3Reliability
If rotating capacitors with rotating and stationary plates are used, then high-voltage isolation is maintained, but device complexity increases
Solution Approach 1:
The capacitor structure incorporates rotating plates that spin within a stationary housing, creating dynamic high-voltage isolation through continuous motion. This dynamic design maintains electrical isolation while allowing signal transmission, resolving the contradiction between maintaining high-voltage isolation and reducing structural complexity compared to static multi-stage isolation systems
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 effectively decreases electrical noise in IVUS imaging systems while adhering to safety standards by ensuring patient safety from leakage currents, even during single-fault conditions, by setting the series capacitance to limit leakage current within safe regulatory limits.
Implementation Method 1
The shield-coupling capacitor is electrically coupled to the conductive shield and includes one or more rotating capacitors
Implementation Method 2
providing a low impedance path for radio-frequency currents and maintaining high-voltage isolation
Data Source
AI summary
A catheter assembly for an intravascular ultrasound system includes a catheter, an imaging core, and a shield-coupling capacitor. The catheter defines a lumen extending along a longitudinal length of the catheter. The imaging core is configured and arranged for inserting into the lumen. The imaging core includes a rotatable driveshaft, one or more transducers, one or more conductors, and a conductive shield. The one or more transducers are mounted to the rotatable driveshaft. The one or more conductors are coupled to the one or more transducers and extend along the driveshaft. The conductive shield is disposed around the one or more conductors. The shield-coupling capacitor is electrically coupled to the conductive shield and includes one or more rotating capacitors. The one or more rotating capacitors include one or more rotating plates and one or more stationary plates. The shield-coupling capacitor is configured and arranged for coupling to a system ground.