Tissue-Removing Catheter Torque Control via Motor Current Feedback
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Solution Overview
Problem
Current tissue-removing catheters lack effective torque control mechanisms, which can lead to over-torqueing and potential damage to the catheter or surrounding tissue during the removal of occlusive tissue in body lumens.
Innovation Solution
A tissue-removing catheter with a motor-driven rotation system and a controller that uses pulse width modulation (PWM) to control the speed of the motor, coupled with a gear assembly and a sensor to monitor and adjust torque, ensuring the catheter operates within predetermined torque limits to prevent over-torqueing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the motor speed is increased to improve tissue removal efficiency, then productivity increases, but torque control becomes difficult leading to potential damage
Solution Approach 1:
The controller continuously monitors motor current and compares it to a threshold value, dynamically adjusting motor speed in response to detected torque conditions. This closed-loop feedback mechanism enables the system to maintain high productivity while preventing over-torqueing by automatically reducing speed when excessive current is detected
Solution Approach 2:
The motor speed is made dynamically adjustable rather than fixed, allowing the controller to vary the PWM duty cycle in real-time based on operating conditions. This dynamic control enables optimization of tissue removal efficiency at low torque while preventing damage at high torque conditions
2Productivity
If the torque limit is increased to remove harder tissue, then productivity improves, but the risk of damaging surrounding tissue increases
Solution Approach 1:
The system uses real-time current monitoring to detect changes in torque load and automatically adjusts motor speed accordingly. When the current approaches the threshold indicating excessive torque, the controller reduces speed to prevent damage, thereby protecting surrounding tissue while maintaining the ability to remove hard tissue at lower torque levels
Solution Approach 2:
The motor operating parameters (speed and current) are changed dynamically during operation based on detected load conditions. The controller modifies the PWM duty cycle to change motor speed in response to current levels, enabling the system to adapt torque application to match the specific requirements of different tissue types
3Reliability
If the motor speed is reduced to control torque, then safety improves, but tissue removal efficiency decreases
Solution Approach 1:
The motor speed is dynamically adjusted based on real-time torque conditions rather than maintained at a fixed low level. The controller uses PWM modulation to vary speed continuously, allowing high efficiency at low torque conditions while automatically reducing speed only when necessary to prevent over-torqueing
Solution Approach 2:
The system changes motor operating parameters adaptively based on detected conditions. The controller monitors current and adjusts speed accordingly, enabling the system to operate at high efficiency when torque is low and automatically reduce speed only when torque approaches dangerous levels
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 system effectively controls torque during tissue removal, preventing damage to the catheter and surrounding tissue, while allowing for efficient removal of occlusive tissue in body lumens, such as in coronary arteries, by dynamically adjusting motor speed and torque based on detected conditions.
Implementation Method 1
A motor operatively engages the elongate body for driving rotation of the elongate body and tissue-removing element mounted on the elongate body
Implementation Method 2
the controller controls the speed of the motor based on a logistic speed control curve
Implementation Method 3
A sensor monitors a speed of the motor
Data Source
AI summary
A tissue-removing catheter for removing tissue in a body lumen includes an elongate body having an axis and proximal and distal end portions spaced apart from one another along the axis. A tissue-removing element is mounted on the distal end portion of the elongate body. The tissue-removing element is configured to remove the tissue as the tissue-removing element is rotated by the elongate body within the body lumen. A motor operatively engages the elongate body for driving rotation of the elongate body and tissue-removing element mounted on the elongate body. A controller is operatively connected to the motor and configured to perform a torque response routine to control a speed of the motor based on a set PWM value of the motor and a detected current applied to the motor during rotation of the elongate body and tissue-removing element.