Transcript In-Vivo
In-Vivo Active Pressure Monitoring System Presented by Mahmoud Mohamed Abdallah Sayed Ahmed The Main Idea • Medical examinations often extract localized symptoms rather than systemic observations and snap shots rather than continuous monitoring. • Using these methodologies, one cannot discretely analyze how a patient’s lifestyle affects his/her physiological conditions and if additional symptoms occur under various stimuli. • So the solution is in a minimally invasive implantable pressure sensing system that actively monitors long-term physiological changes in real-time. The Main Idea • Kidney stones, ureter strictures, tumors, and uretopelvic junction obstruction block the upper urinary track. And a Symptom of urinary blockage is elevated pressure. • So the system investigates pressure changes in the upper urinary tract per degree of obstruction. • An implantable active pressure sensor has been developed for the continuous measurement of elevated pelvic and ureteral renal pressures. The Main Idea • Benefits of the in-vivo pressure monitoring system: 1. The continuous, active monitoring of pressure within the upper urinary track 2. The real-time automated distribution of data to a patient’s PDA 3. The aggregation of data to a online database that stores information for later analysis of the symptoms 4. The remote in-vivo reconfiguration of the software The Main Achievements • System Architecture: Sensor Skin Sensor Node The Main Achievements • The system integrates three components: – Sensor Node: Mica2Dot(Atmega 128L microcontroller and wireless transmitter) with a signal conditioning circuit and battery. – Pressure Sensor: ultra-small, low-cost OEM pressure die. – Base Station: a pocket PC that gathers and processes data from the sensor node. • The System Operation: 1. The Mica2Dot sends pressure readings to a PDA/Pocket PC. 2. The PDA visualizes the data and can perform more complex data processing, such as decision support The Main Achievements • Features: – wire-free system measures pressure – Working hours: forty-eight hours – Range: twenty feet away – Remotely reconfigurable software – The multi-channel transmitter is has a center frequency of 868/916 Mhz with adata rate of 38.5 kbps. – The radio uses 27mA of power while transmitting and 10mA of power while receiving The Main Achievements • In-vivo active pressure monitoring system unique features: 1. Active Pressure Monitoring (own internal power supply) • Higher transmission range • Ubiquity in deployment • communicate with such as PDAs. 2. Collection Mechanism • Uploads the data to an online database. • This allows for the later analysis of the data to determine patterns in how one’s lifestyle affects the internal urinary track pressure and the long-term progression of urinary track blockage. The Challenges • Pressure Transducers – The desired range of pressure sensing in the application was 0 to 1 PSI with accuracy of 0.02 PSI. – So the voltage span will be approximately 6mv. – The small degree of voltage can be considerably affected by environmental noise. – The voltage range must fully utilize the 0 to 3 voltage range The Challenges • Pressure Transducers The Challenges • Pressure Transducers – So precise signal conditioning circuit is developed for: • Stabilizing excitation voltage: The sensor excitation voltage needs to be steadied at 3V. • Electrical noise reduction: Considerable noise is generated within the circuit and must be accurately filtered out. • Voltage amplification • Offset voltage removal: The sensors bridge is not symmetric when no pressure is applied. This lack of symmetry results in an offset voltage that reduces the voltage swing between 0 to 1 PSI. The Challenges • Catheter Design – The Catheter must be • Biocompatible • Maneuverable – So The conductors are individually PTFE insulated and the catheter body is sheathed in silicone rubber. – The conductors are soldered to bonding pads on a PCB substrate and encapsulated with biocompatible epoxy. – The monitoring system includes stress relief measures to ensure additional robustness and to relieve the anticipated forces exerted on the system during packaging and implantation,. The Challenges • Catheter Design The Challenges • Biocompatible Packaging – Unsatisfactory packaging can: • Degrades the performance of the sensor • Result in device failure • Result a severe immunogenic response from the subject – Most researchers package their implantable sensors with only silicone dipping or parylene. – However, most silicones are not designed to be used internally and parylene has been shown to attract immunogenic cells. The Challenges • Biocompatible Packaging The Challenges • Biocompatible Packaging – The system is packaged with two dual passivation layers: • parylene – conforms to any geometry on the micro-scale. – high resistance to permeation and solvent absorption – strengthens wire bonds at interfaces. • medical grade encapsulant. – excellent bulk property – malleability to surface properties. – The sensor was evaporated a thin layer of parylene to combat the volatile environments in the body and the harsh chemicals in post processing.