Implantable pressure sensor
Inventors
Damaser, Margot S. • Majerus, Steven • Fletter, Paul C. • Garverick, Steven L. • Ko, Wen H. • Zaszczurynski, Paul
Assignees
Cleveland Clinic Foundation • Case Western Reserve University • US Department of Veterans Affairs
Publication Number
US-10143391-B2
Publication Date
2018-12-04
Expiration Date
2033-05-08
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Abstract
Systems and methods are provided for in vivo measurement of pressure. An implantable sensor assembly includes a pressure sensor configured to provide an analog signal representing pressure and a signal conditioning component configured to convert the pressure sensor output into a digital signal. A transmitter is configured to transmit the digital signal to an external base unit. A power control unit is configured to dynamically allocate power throughout the implantable sensor assembly, such that during an active measurement interval of the implantable sensor assembly, each of the pressure sensor, the signal conditioning component, and the transmitter are powered only for a portion of the active measurement interval necessary to perform a related function.
Core Innovation
The invention provides systems and methods for in vivo measurement of pressure using an implantable sensor assembly. This assembly includes a pressure sensor that outputs an analog signal representing pressure, a signal conditioning component that converts this analog signal into a digital signal, and a transmitter that sends the digital signal to an external base unit. A key innovation is the power control unit which dynamically allocates power throughout the implantable sensor assembly during active measurement intervals so that each component is powered only for the portion of time necessary to perform its function.
The sensor assembly is designed for chronic or short-term implantation in body sites such as the bladder, to provide feedback for medical diagnostics or treatments. It features a microbattery rechargeable via inductive coupling with the external base unit. The system minimizes power consumption by selectively powering the pressure sensor, signal conditioning, and transmitter only when needed within each measurement cycle, resulting in greatly reduced average power use as compared to traditional devices that keep all components powered continuously or in simple sleep modes.
Claims Coverage
The patent includes two independent claims, both directed to an in vivo sensor assembly with a pressure sensor, signal conditioning component, transmitter, and a dynamic power control unit. Below are the main inventive features as claimed.
Dynamic power allocation within implantable sensor assembly
The assembly includes a power control unit configured to transition the sensor from inactive to active mode at a predetermined frequency with an active measurement interval, dynamically allocating power so that the pressure sensor, signal conditioning component, and transmitter are each powered only during necessary subintervals within the active measurement period.
Selective powering of components within measurement interval
Within an active measurement interval of approximately one millisecond at frequencies between twenty and one hundred hertz, each component—the pressure sensor, signal conditioning component, and transmitter—has a necessary power interval less than the full active interval, during which it is powered only when performing its related function, allowing components to be off during parts of the active interval.
Inclusion of offset removal component in signal conditioning
The signal conditioning component includes an offset removal component that calculates a correction value based on the average of a predetermined number of previous samples, allowing dynamic compensation for slow pressure changes or shifts.
Forced and automatic offset calibration modes
The offset removal component can respond to external commands to perform a forced offset calibration by rapidly taking multiple measurements to null the system offset, in addition to automatic operation that maintains average pressure readings centered within the measurement dynamic range.
Integration on single application-specific integrated circuit (ASIC)
The signal conditioning component, transmitter, and power control unit are implemented as a single ASIC chip within the implantable sensor assembly.
Power sequencing with partial non-overlapping power intervals
The transmitter is powered during a portion of the active interval when neither the pressure sensor nor the signal conditioning component is powered, and the signal conditioning component is powered during a portion when the pressure sensor is not powered, enabling staggered and minimal power consumption.
In sum, the inventive features focus on a dynamic and finely controlled power management method within an implantable pressure sensor assembly, including selective powering of sensor components during a brief active measurement interval, integration on a single ASIC, and offset correction mechanisms, all enabling low power consumption and long-term implantability.
Stated Advantages
Greatly reduced power consumption of the implantable sensor assembly by dynamically allocating power only when necessary within each active measurement interval.
Improved wireless power transfer efficiency enabled by power status feedback conveyed to the external recharger, minimizing patient exposure to strong electromagnetic fields.
Capability for chronic implantation with small battery capacity by extending device operation between charges using the 'sample conveyer' power management approach.
Enhanced signal quality and measurement accuracy through offset removal and low noise amplifier designs compatible with low power operation.
Documented Applications
Long-term chronic monitoring of bladder pressure for diagnostic purposes and feedback in treatments such as electrical stimulation to manage voiding dysfunction or urinary incontinence.
Short-term diagnostic monitoring of bladder pressure wherein a sensor floats in the bladder, possibly measuring bladder volume, with data recorded or transmitted externally and the device extracted after a short period.
Applications in neuromodulation where the implantable pressure sensor transmits data to an external neural stimulator that monitors pressure and triggers stimulation based on detected abnormal events.
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