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1Healthy Aims IST-2002-1-001837
Wireless Pressure Sensor System for Intracranial Pressure Monitoring
Campus Micro TechnologiesDr. Manfred Frischholz
info@campus-micro-technologies.de
2Healthy Aims IST-2002-1-00183701.1
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deSmart Sensing Solutions for Life
� CMT provides smart sensing solutions for the medical community� CMT has specialized in developing highly miniaturized sensor
systems for medical applications� Short or long-term implants for measuring and monitoring vital
parameters in the human body
We have developed solutions for� neurosurgical
� ophthalmic,� and cardio-vascularapplications for our customers
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deOur Vision
� “Young and aging population will profit from continuous monitoring of vital parameters and availability of medical support at any time and place in their everyday life.“
� „Medical aid is already on its way to the patient before any signs of health problems become noticeable for the patient himself.“
� “Preventive measures improve health conditions and quality of life“
Do you feel
alright?
We better send
someone now!
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deSensors for Continuous Monitoring of
Vital Parameters
� Long-existing wish for implantable sensors for short-term or chronic measurement of physiological parameters
� Still only very few medical products on the market today� Main reasons: technological barriers
� Size� Stability� Reliability� Power consumption (lifetime of the battery)
Today‘s pace makers include sensors and make use of micro- and nanotechnologies (electrodes)
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deTechnological Progress
� Miniaturization of sensors using micro systems technology (derived from microelectronics)
� Reproducibility and stability� Performance and degree of miniaturization of microelectronic components� Reduced power consumption of electronic components (rapid development in
mobile communication sector)� Advancements in assembly and packaging technologies (flexprints, gold on
polymer films, conductive glueing) � Materials development for barrier layers and encapsulation (humidity and
water uptake) � Availability of advanced technology outside of original field of application
(increase of interdisciplinary work)
Today all (or most) of the necessary technology for the use of wireless sensor systems in competitive medical products exist
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6Healthy Aims IST-2002-1-001837
Telemetric Pressure Monitoringin Neurosurgery
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deNeurosurgical Applications
1. ICP monitoring in the clinical management of severe head injury and other conditions causing high ICP� Alternative approach to conventional tip
transducers
2. Continuous monitoring of ICP in hydrocephalus patients � Monitor shunt performance in-vivo� Therapy optimization
3. Closed-loop hydrocephalus shunts� Feedback-controlling� Event-driven therapy
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deNeuromonitoring
� ICP monitoring in the management of severe head injury
� Today‘s techniques use strain gauge tip transducers and intraventricular catheters
� Main pitfalls of today’s techniques
http://connection.lww.com
High risk of infection
Catheter occlusion
Needs reposting of transducer level with change in head position
Intraventricularcatheter
Increasing drift over time
High risk of infection
Reduction of patient mobility
Tip transducer
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deCurrent Status in Neuromonitoring
Cannot be recalibrated after it is placed, unless a ventriculostomy is used simultaneously for referenceBreakage of fiberoptic cableHigh cost
Can be placed in the subdural, subarachnoid, intraventricular or intraparenchymal spacesEasily transportedMinimal artefact and driftHigh resolution of waveformNo irrigation less risk of infectionNo need to adjust for patient position
Fiberopticprobe/catheter tip strain gauge
Increasing baseline drift over time, accuracy and reliability are questionable Does not provide CSF sampling
Least invasiveEasily and quickly placed
Subdural/epidural catheter/sensor
Blocked by swollen brainCatheter can be occluded by tissue or bloodMust be balanced and recalibrated frequently
Quickly and easily placedDoes not invade brainAllows sampling of CSFMay have lower infection rate
Subarachnoidbolt/screw
Most invasiveSometimes difficult to cannulate ventricleCatheter can be occluded by blood or tissueNeeds reposting of transducer level with change in head positionPotential infection
Gold standard of accuracyAllows drainage and sampling of CSFAllows ICP controlInexpensive
Intraventricularcatheter
Pitfalls Advantages Device
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Holloway KL, Barnes T, Choi S, et al. Ventriculostomy infections: the effect of monitoring duration and catheter exchange in 584 patients. J Neurosurg 85:419-424, 1996.
Increased Risk of Infection due to Percutaneous Monitoring
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deHydrocephalus
� Hydrocephalus describes state of excessive accumulation of CSF within the fluid system of the head causing high intracranial pressure
� Therapy: draining CSF from the CNS by shunts
� NPH market: 375,000 cases each year in the U.S., $500 Mio market size
� Approx 40 per 100,000 Individuals have shunts in place
� Shunt failure � 40% shunts fail in 1st year, 50% by 2nd year� Shunts are revised about two times in the first
ten years of use per patient!
� There is currently no practical way to measure shunt performance in vivo!
www.motiv-medtech.comCSF – Cerebro Spinal FluidCNS – Central Nervous SystemNPH – Normal Pressure Hydrocephalus
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““Although numerous experimental techniques have Although numerous experimental techniques have been developed, there is currently no practical been developed, there is currently no practical
way to measure shunt performance in vivo”way to measure shunt performance in vivo”
Ginsberg HJ and Drake JM (2004). Physiology of Cerebrospinal FluGinsberg HJ and Drake JM (2004). Physiology of Cerebrospinal Fluid Shunt Devices.id Shunt Devices.
In: Yeoman’s Neurological Surgery, Fifth Edition.In: Yeoman’s Neurological Surgery, Fifth Edition.
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deRequirements
� Miniaturized and flexible for minimal invasive delivery� Wireless communication� No battery or internal power source� Highly biocompatible
� Wave form analysis � Minimal drift and temperature stable � Easy measurement at home
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deSystem Overview
Interface
Modulation
Voltage
regulator
AC
DC
Power
RF-transmitter
Demodulator
Interface
Interface
Signal
processing
Pressure
sensor
Reference
Body
Area
Network
Interface
Wireless power and data
transmission
Pressure sensing tipInternal telemetry unitExternal telemetry unit
SkinPressure
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deSystem Overview (Cont.)
Inductive coupling
RF communication
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dePrototypes
Flexible substrate
Encapsulation into polymer
Electronics FC/SMD on flex
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deDevice Characteristics
� Telemetric powering and data read-out
� Intraventricular or parenchymal measurement
� ‘Drift-free’ capacitive pressure sensor
� Temperature stable readings� Dynamic measurement
possible� Easy to insert and position;
flexible
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deDevice Benefits
� Scalp barrier reduces risk of infection
� Minimal drift of sensor� Prolonged monitoring possible� No replacement required
� Independent from shunt therapy
� Home monitoring � Therapy control and
optimization
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deDevelopment Roadmap
2007200620052004
P8P7P6P5P4P3P2P1
Clinical trials and regulatory approval process
Frenchay Hospital, UK
2nd prototypeSystem optimization and
Design validation
Functional demonstratorComplete assembly:
SMT & FC on flex circuit
EU Market launch
Spin-off applications
Further miniaturizationNew pressure sensor
Bench testingSystem design verification, in bench tests and animal model
1st prototypeSMT & FC on flex circuit;Polymer encapsulation &
Biocompatible barrier coating
Quality managementISO 13485:2003
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deSpin-Off Applications
� Monitoring endoluminal stent-grafts in abdominal aortic aneurysm repair
� Home monitoring of patients suffering from congestive heart failure� Wireless monitoring of urinary bladder pressure
� …
� Feed-back systems for gentle control and therapy-optimization
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deHealthy Aims Partner
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deConclusion
� Wireless pressure sensor systems will fill the current gap for neurosurgical applications in the near future
� High integration of technology partners during development enables the introduction of new add reliable products.
� Close collaboration with clinical end-users guarantees development in line with the market needs and medical requirements.
� Technology and concept is applicable to a large range of medicalapplications and sensors (other than pressure sensors)
� Implantable telemetric sensor systems will be of significant value for cost-effective continuous monitoring of therapeutic procedures even under everyday life conditions.
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