wireless pressure sensor system for intracranial … healthy aimsist-2002-1-001837 1 wireless...

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1Healthy Aims IST-2002-1-001837

Wireless Pressure Sensor System for Intracranial Pressure Monitoring

Campus Micro TechnologiesDr. Manfred Frischholz

[email protected]

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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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Campus Micro Technologies GmbHUniversitätsallee 29

28359 BremenGermany

T: +49 (0)421 20 20 783F: +49 (0)421 20 20 900

info@campus-micro-technologies.dewww.campus-micro-technologies.de

wireless pressure sensor system for intracranial … healthy aimsist-2002-1-001837 1 wireless...

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