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last lecture: Biofeedback: Principles and Applications

last lecture: Biofeedback: Principles and Applications Brain Computer Interfaces – Theory and Methods. today: Design Standards for biomedical devices Device Certification File Formats and Data Transfer Standards. Safety of medical devices. ● Electrical Safety

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last lecture: Biofeedback: Principles and Applications

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  1. last lecture: Biofeedback: Principles and Applications Brain Computer Interfaces – Theory and Methods

  2. today: Design Standards for biomedical devices Device Certification File Formats and Data Transfer Standards

  3. Safety of medical devices ● Electrical Safety double Isolation, safety grounding, clearence galvanic isolation, isolation barriers ● Electrostatic Discharge (ESD-) Protection prevention of device damage or degradation of protective circuits ● Electromagnetic Compatibility (EMC, EMV) capacitive or inductive coupling, resonance RF / radiation levels, device interference ● Software Safety ● biocompatibility, radiation, riskmanagement, …

  4. International and National Organisations: International Electrotechnical Commission (IEC) International Organization for Standardization (ISO) Institute of Electrical and Electronics Engineers (IEEE) Comité international spécial des perturbations radioélectriques (CISPR) (Internationales Sonderkomitee für Funkstörungen) European Committee for Electrotechnical Standardization (CENELEC) European Telecommunications Standards Institute (ETSI) American National Standards Institute (ANSI) Österreicisches Normungsinstitut

  5. Current European Union regulation ● based on the “New Approach” (CE marking) ● applicable processes depend on risk-category ●government-appointed Notified Bodies certify the conformity assessment procedures ● improvements often result from user feedback

  6. Methods to assure Safety ● Certification and harmonization of design standards Directive 93/42/EWG Medical products Directive 90/385/EWG Active implants Directive 98/79/EG In-vitro diagnostic devices ISO / EN 60601-2 EN 540 (EN ISO 14155) clinical Evaluation EN 1041 Information by the manufacturer ● Risk management and labelling EN 1441 risk analysis, EN ISO 14971 risk management EN 980 Graphical symbols and labeling

  7. Methods to assure Safety ● Safety-ZonesNo-Cell Phones in critical areas, no metallic objects near MRI, … ● Dependability, Fail-Safety, Fault Tolerance Redundancy in Hardware and Software ● Guidelines „MEDDEVS“ of the European Comission NB-Med Recommendations Global Harmonization Task Force (GHTF)

  8. Law for the admission of medical devices: Österreichisches Medizinprodukte= gesetz (MPG), BGBl. Nr. 657/1996: ● Definition of medical devices ● Classification of risk ● CE – admission ●clinical evaluation ● Registration, responsibility: menufacturer, seller, … ● intended usage

  9. Electrical Safety - some definitions Clearance: The shortest distance between two conductive parts, or between a conductive part and the bounding surface of the equipment, measured through air Hazardous Energy Level: A stored energy level of 20J or more, or an available continuous power level of 240 VA or more, at a potential of 2V or more. Hazardous Voltage: A voltage exceeding 42.4V peak or 60V d.c., existing in a circuit which does not meet the requirements for either a Limited Current Circuit or a TNV Circuit. Limited Current Circuit: A circuit which is so designed and protected that , under both normal conditions and a likely fault condition, the current which can be drawn is not hazardous. Safety Critical: A component which affects the safety of the equipment. All components in primary circuitry are safety critical. Other components which protect the equipment under normal and fault conditions, such as thermal switches, optocouplers, etc. are also safety critical.

  10. Electrical Safety - some definitions Touch Current: Electric current through a human body when it touches one or more accessible parts. (Touch current was previously included in the term 'leakage current') Insulation according to IEC 664 / VDE 0110 (1/89): Data for insulation coordination requires values for rated voltage, pollution degree and overvoltage category. Overvoltage category: Classification of electrical equipment to the overvoltage to be expected. Surge voltage: Amplitude of a voltage impulse of short duration with a specified impulse form and polarity that is applied to test insulation paths in device/component. This proves that the device/component (for example relay) will withstand very high overvoltages for very short periods.

  11. Electrical Safety - some definitions Class I: Equipment where protection against electric shock is achieved by using basic insulation, and also providing a means of connecting to the protective earthing conductor in the building wiring those conductive parts that are otherwise capable of assuming hazardous voltages if the Basic Insulation fails. Class II: Equipment in which protection against electric shock does not rely on basic insulation only, but in which additional safety precautions, such as double insulation or reinforced insulation, are provided, there being no reliance on either protective earthing or installation conditions. Medical types B and BF (EN60601): Maximum leakage 100 microamperes, 4000V voltage rating with 60 second test Medical type CF (EN60601): Maximum leakage 10 microamperes, 4000V voltage rating with 60 second test

  12. Electrical safty - IEC 60601 examples Safety Class I metallic enclosure grounded via earth wire Safety Class II enclosure seperated with double or hardened isolation Safety Class III Power Supply <= 25V AC Example guidelines for electrical isolation

  13. Device types, labels - IEC 60601 examples ● device type B („body“) Leakage current < 0.1 mA Can be grounded ●device type BF („body floating“) Leakage current < 0.1 mA Isolated from ground ● device type CF („cardiac floating“) Leakage current < 0.01 mA special Isolation

  14. EMC - European standards EN 55011 Interference emission from industrial, scientific and medical devices (ISM appliances) EN 55013 Interference emission from radio receivers and consumer electronic appliances EN 55020 Interference immunity of radio receivers and consumer electronic appliances EN 55014-1 Interference emission from household appliances EN 55014-2 Interference immunity of household appliances EN 55015 Interference emission from electric lighting equipment EN 61547 Interference immunity of electric lighting equipment EN 55022 Interference emission from information technology equipment (IT appliances) EN 55024 Interference immunity of information technology equipment (IT appliances) EN 61000-4-2 Interference immunity to electrostatic discharge (ESD) EN 61000-4-3 Interference immunity to electromagnetic fields EN 61000-4-4 Interference immunity to fast transient orders of interference (burst) EN 61000-4-5 Interference immunity to surge voltage EN 61000-4-6 Interference immunity to conducted orders of interference induced by high frequency fields EN 61000-4-8 Interference immunity to magnetic fields with energy technology frequencies EN 61000-4-11 Interference immunity to voltage drops, short-time interruptions and voltage fluctuations EN 50081-1 Interference emission from appliances in the household area EN 50081-2 Interference emission from appliances in the industrial area EN 50082-1 Interference immunity of appliances in the household area EN 50082-2 Interference immunity of appliances in the industrial area EN 61000-6-2 Interference immunity of appliances in the industrial area EN 61000-3-2 Reactions in electricity supply systems - harmonic oscillations EN 61000-3-3 Reactions in electricity supply systems - voltage fluctuations EN 60601-1-2 EMC medical electric appliances

  15. ESD Protection - Standards ANSI ESD STM5.1:2001—Electrostatic discharge sensitivity testing—Human body model. ANSI ESD STM5.2:1999—Electrostatic discharge sensitivity testing—Machine model. ANSI ESD STM5.3.1:1999—Charged device model (CDM)—Component level. ESD Association Advisory Documents : ESD ADV1.0:2004—Glossary of terms. IEC 61000-4-2:1995—Electromagnetic compatibility (EMC)—Part 4: Testing and measurement techniques—Section 2: Electrostatic discharge immunity test; Amendment 2:2001. IEC 61340-2-2:2000—Electrostatics—Part 2-2: Measurement methods—Measurement of chargeability. IEC 61340-2-3:2000—Electrostatics—Part 2-3: Methods of test for determining the resistance and resistivity of solid planar materials used to avoid electrostatic charge accumulation. IEC 61340-3-1:2002—Electrostatics—Part 3-1: Methods for simulation of electrostatic effects—Human body model (HBM)—Component testing (IEC/101/33/CD). IEC 61340-3-2:2002—Electrostatics—Part 3-2: Methods for simulation of electrostatic effects—Machine model (MM)—Component testing (IEC/101/34/CD). IEC 61340-4-1:2003—Electrostatics—Part 4-1: Standard test methods for specific applications—Section 1: Electrostatic behavior of floor coverings and installed floors.

  16. Product Safety Standards – IEC 60601 IEC 60601-1:2005—Medical electrical equipment—Part 1: General requirements for safety. IEC 60601-1-2:2004—Medical electrical equipment—Part 1: General requirements for safety—Section 2: Collateral standard—Electromagnetic compatibility—Requirements and tests; Amendment 1:2004. IEC 60601-1-3:1994—Medical electrical equipment—Part 1: General requirements for safety—Section 3: Collateral standard—General requirements for radiation protection in diagnostic x-ray equipment. IEC 60601-1-4:2000—Medical electrical equipment—Part 1-4: General requirements for safety—Collateral standard: Programmable electrical medical systems. IEC 60601-2-1:1998—Medical electrical equipment—Part 2-1: Particular requirements for the safety of electron accelerators in the range of 1 to 50 MeV; Amendment 1:2002. IEC 60601-2-2:1998—Medical electrical equipment—Part 2-2: Particular requirements for the safety of high-frequency surgical equipment. IEC 60601-2-3:1991—Medical electrical equipment—Part 2-3: Particular requirements for the safety of short-wave therapy equipment; Amendment 1:1998. IEC 60601-2-4:2002—Medical electrical equipment—Part 2-4: Particular requirements for the safety of cardiac defibrillators and cardiac defibrillator monitors. IEC 60601-2-5:2000—Medical electrical equipment—Part 2-5: Particular requirements for the safety of ultrasonic physiotherapy equipment.

  17. Product Safety Standards – IEC 60601 IEC 60601-2-25:1993—Medical electrical equipment—Part 2-25: Particular requirements for the safety of electrocardiographs; Amendment 1: 1999. IEC 60601-2-26:2002—Medical electrical equipment—Part 2-26: Particular requirements for the safety of electroencephalographs. IEC 60601-2-27:2005—Medical electrical equipment—Part 2-27: Particular requirements for the safety of electrocardiographic monitoring equipment. IEC 60601-2-28:1993—Medical electrical equipment—Part 2-28: Particular requirements for the safety of x-ray source assemblies and x-ray tube assemblies for medical diagnosis. IEC 60601-2-29:1999—Medical electrical equipment—Part 2-29: Particular requirements for the safety of radiotherapy simulators. IEC 60601-2-30:1999—Medical electrical equipment—Part 2-30: Particular requirements for the safety, including essential performance, of automatic cycling noninvasive blood pressure monitoring equipment. IEC 60601-2-31:1994—Medical electrical equipment—Part 2-31: Particular requirements for the safety of external cardiac pacemakers with internal power source; Amendment 1:1998.

  18. Product Safety Standards – others ISO 11197:2004—Medical electrical equipment—Particular requirements for safety of medical supply units ISO/TR 16142:2006—Medical devices—Guidance on the selection of standards in support of recognized essential principles of safety and performance of medical devices ISO/IEC Guide 63:1999—Guide to the development and inclusion of safety aspects in international standards for medical devices IEC 60513:1994—Fundamental aspects of safety standards for medical electrical equipment. EN 793:1998—Particular requirements for safety of medical supply units. EN 45502-1:1998—Active implantable medical devices—Part 1: General requirements for safety, marking, and information to be provided by the manufacturer EN 50061—Medical electrical equipment—Safety of implantable cardiac pacemakers EN 61204:1995—Low-voltage power-supply devices, dc output—Performance characteristics and safety requirements; Amendment 1:2002 EN 60950:2000—Safety of information technology equipment; Corrigendum: 2002 CISPR 11 - Industrial, Scientific and Medical (ISM) Radio-Frequency Equipment -- Electromagnetic Disturbance Characteristics -- Limits and Methods of Measurement.

  19. Product Safety Standards – IEC 60601 Summary of first and Second edition

  20. Software as a medical product ● Control algorithms for medical hardware CT, pacemaker, … ● Data evaluation, visualisation ●Expert systems, databases ●Computer aided surgery, Tele-medical applications ● Risk Management Processes became essential adapted from IEC 60601-1-4 ● CDRH Center for Devices and Radiological Health Guidance for the Content of Premarket Submissions for Software Contained in Medical Devices

  21. What does this all mean for our EEG device ? Steps to get an EN-60601 CE certification: ● improvement of ESD protection for all inputs +15kV, especially for the amplifier input pins (IEC 1000-4-2) ●improvement of isolation barrier (DC/DC converter and optocouplers) to withstand 3kV permanently ●calibration procedurces in software, impedance checking ● certification by notified bodies: Österreichisches Normeninstitut, TÜV ● last but not least: some money (do not try this at home without € 20000 at hands )

  22. Electrostatic Discharge Protection

  23. ESD: ● One root cause of equipment failure ●Can happen during production and in field ●Errors often difficult to track, degrading performance Example: RS232 interface chip after exposure to an ESD event of 15kV

  24. ESD: Origin of electrostatic chargeing - triboelectric effect: materials with opposite surface charges come together transfer of electrons from one material the other seperation leaves a net-negative and a net-positive charge

  25. ESD: ● low humidity prevents localized charges from moving ●Interaction of people with their surrounding can produce significant charge: Human body model: 100pF capacitance charged upt to 15kV 1500 Ohm series resistance When discharged, this setup produces a very fast rise time with peak current of 15kV/1500Ohm = 10 A

  26. ESD Testing standards ● Chip package pins are tested against other groups of pins ●I/O pins should be tested seperately

  27. ESD Testing standards Four Levels of ESD compliance in the IEC 100-4-2 standard: Contact and Air Gap discharge

  28. ESD Testing Electron Microscope View of a Fused Metallization Site, as a Result of Electrical Overstress Example ESD waveform: rise time, peak current, amplitude at 30 an 60 ns

  29. ESD protection strategies / guidelines ● Capacitor protection / Resistor Protection to limit voltage / current Layout and design compatibility needed ● Metal oxide varistors / silicon avalanche suppressor (TransZorb) ●Place bypass and charge-pump capacitors close to IC or I/O-port ● Include a ground plane on the PCB ● Use protection ICs (e.g. NUP 4201) and/or ESD protected ICs ● Proper grounding of persons and facility ● Suitable power up strategy for the circuit, consider maximum ratings Further reading: Maxim Application Note 639 on ESD

  30. Sources / Links ●Dr. Wolfgang Ecker: Skriptum Medizinproduktegesetz: http://cis.technikum-wien.at/documents/bbe/5/srk/download/ ● Articles by EisnerSafety http://www.eisnersafety.com ● Österr. Verband für Elektrotechnik (www.ove.at) ● Österr. Normungsinstitut (www.on.at) ● International Electrotechnical Commission (www.iec.ch) ● European directives http://ec.europa.eu/enterprise/medical_devices/index_en.htm http://ec.europa.eu/enterprise/electr_equipment/emc/ http://ec.europa.eu/enterprise/newapproach/legislation/guide/index.htm ● US Food and Drug Administration / Center for Devices and Radiological Health (www.fda.gov/cdrh)

  31. Standards for Communication and Modelling

  32. DICOM – Digital Imaging and Communications in Medicine ● developed by ACR (American College of Radiology) and NEMA (National Electrical Manufacturers Association ) ● main purpose: transfer of image data (CT images) ● overcomes file format incompatibilities ●allows creation of distributed databases (TCP/IP) ●specifies semantics of commands and associated data ● Information Objects for images, waveforms, reports, printing … ● specifies levels of conformance, not implementation details

  33. DICOM – General Communication Model ● Upper Layer service provides independence from physical networking ● Basic File Service provides storage media access

  34. DICOM Parts and Application Profile Example configuration of an application, corresponding DICOM Parts

  35. HL7 - Health Level Seven ● Non-Profit organisation, developing standards for exchange of clinical and administrative data ● HL7 Reference Information Model (RIM) representation of clinical data domains ● Special Interest Groups develop vocabulary, XML-integration, Messaging Standards ●Objectives:Messaging/Protocols, Query Sturctures, Medical Records Patient Administration / Financial Management, Clinical Order Entry, Laboratory Automation, Application Management, Personnel Management Security in Data Exchange (in respect to HIPAA, the Health Insurance Portability and Accountability Act, 1996)

  36. HL7 - Reference Information Model (RIM)

  37. CDISC - Clinical Data Interchange Standards Consortium ● CDISC develops industry standards for electronic acquisition, exchange, submission and archiving of clinical trials data ●Study Data Tabulation Model (SDTM): Metadata Variable definitions: name, type, origin, role Observation Classes: Interventions (medication etc.), Events, Findings Relationships among Datasets and Records Trial Design Model

  38. File Formats for physiological data

  39. File Formats: Proprietary EEG recording formats Neuroscan AVG, CNT and EEG EEG, PAT, EVT Nervus/Profile EEG, PAT, EVT, VIDEO Nicolet AllianceWorks Intuition EEG, PAT, EVT Nicolet BMSI 5000 EEG, PAT, EVT, VIDEO Nicolet BMSI 6000 EEG, PAT, EVT, VIDEO Nicolet Bravo Intuition EEG, PAT, EVT, VIDEO Nicolet EEG Vue EEG, PAT, EVT Nicolet UltraSom NT EEG, PAT, EVT Nicolet Voyageur EEG, PAT NCI Uniquant EEG, PAT, EVT, VIDEO Nihon Kohden 2100 EEG, PAT, EVT Persyst Layout (Exported Data) EEG Schwarzer/OSG EEG, PAT, EVT Stellate Harmonie EEG, PAT, EVT Telefactor TUFF EEG, PAT TMSI SMP EEG, PAT Walter Graphtek EEG, PAT, EVT Alpha-Trace DigitalEEG EEG, PAT, EVT ASA (ANT Software B.V.) EEG Axon Instruments EEG, PAT Bio-logic CEEGraph1 EEG, PAT Cadwell EEG, PAT, EVT Cleveland Clinic Vangard EEG, PAT, EVT EBNeuro Galileo DOS EEG, PAT, EVT EBNeuro Galileo NT EEG, PAT, EVT EEProbe AVR (ANT Software B.V.) EEG, EVT Electrical Geodesics (EGI) EEG, PAT EMS Pegasus 1 and 2 EEG, PAT European Data Format EEG, PAT, EVT Excel Tech NeuroWorks EEG, PAT, EVT Micromed BrainQuick EEG, PAT, EVT, VIDEO MPI Nijmegen (MPIData) EEG, PAT EEG: EEG Data , PAT: Patient Information, EVT: Event Data, MNT: Montage Information, VIDEO: Digital Video Data Source: http://www.eemagine.com/fileformats.htm

  40. File Formats: European Data Format - EDF and EDF+ ● Simple format for exchange and storage of multichannel biological signals ● Defacto standard for EEG recordings ●EDF was published in 1992, EDF+ in 2003 ●EDF+ suports annotations and events -> EP, sleep stages etc. ●Hundreds of EDF+ files and several EDF+ viewers available on the internet ● format description and demo applications: http://www.edfpuls.info

  41. File Formats: EDF - structure HEADER RECORD 8 ascii : version of this data format (0) 80 ascii : local patient identification 80 ascii : local recording identification 8 ascii : startdate of recording (dd.mm.yy) 8 ascii : starttime of recording (hh.mm.ss) 8 ascii : number of bytes in header record 44 ascii : reserved 8 ascii : number of data records (-1 if unknown) 8 ascii : duration of a data record, in seconds 4 ascii : number of signals (ns) in data record ns * 16 ascii : ns * label (e.g. EEG Fpz-Cz or Body temp) ns * 80 ascii : ns * transducer type (e.g. AgAgCl electrode) ns * 8 ascii : ns * physical dimension (e.g. uV or degreeC) ns * 8 ascii : ns * physical minimum (e.g. -500 or 34) ns * 8 ascii : ns * physical maximum (e.g. 500 or 40) ns * 8 ascii : ns * digital minimum (e.g. -2048) ns * 8 ascii : ns * digital maximum (e.g. 2047) ns * 80 ascii : ns * prefiltering (e.g. HP:0.1Hz LP:75Hz) ns * 8 ascii : ns * nr of samples in each data record ns * 32 ascii : ns * reserved DATA RECORDSnr of samples[1] * integer : first signal in the data record nr of samples[2] * integer : second signal .. nr of samples[ns] * integer : last signal

  42. File Formats: Physionet and the WFDB tools ● WFDB: Waveform Database a set of tools to read, annotate and convert physiological data from the physiobank archive ● WFDB toolset includes c-libraries, signal viewers, data and file conversion tools ● supported formats: AHA, HEA, MIT/BHI, Netfiles (remote on the web) header-, signal-, annotation- and calibration files ● Link to physionet and the physiobank archives: http://www.physionet.org

  43. BIOSIG Toolbox, other file formats: Biosig Toolbox by Alois Schlögl (TU-Graz) : accessible from C / Python / Matlab / Octave more than 30 import filters for common file formats signal analysis tools ● BDF : a 24 bit extension of EDF, developed by BIOSEMI ● GDF/BKR : defined by TU-Graz ● DDB/DDF : Daisylab Data Files ●MFER: medical waveform encoding rules ●CEN/FEF: file exchange format for vital signs ●DAT: brain atlas EEG data file structure ●SIGIF: signal interchage format Further information about file formats and the biosig toolbox: http://hci.tugraz.at/schloegl/matlab/eeg http://biosig.sourceforge.net/

  44. The IEEE 11073 family of standards : Personal Telehealth Devices - Point of Care medical device communication

  45. IEEE 11073 – The Scenario: E-Health Integration Telecare Technology Vision: E-Health Interaction and Integration

  46. Origins: IEEE 1073 “MIB”: Medical Information Bus IEEE 1157 “MEDIX” : Medical Data Exchange

  47. IEEE 11073 family of standards ● device standards for controlling information exchange to and from personal telehealth devices and cell phones, personal computers, personal health appliances and other compute engines ●codes, formats and behaviors in a telehealth environment to favor plug-and-play interoperability ●Capture and integration of medical instrumentation data generated at the point of patient care to achieve a better understanding of the condition of the patient ● CEN, ISO and IEEE cooperate to solve to the problem of proprietary device- and communication standards ● could provide a link between device-level data and HL-7 long term health records

  48. IEEE 11073 family of standards IEEE P11073-00103: Technical Overview: data exchange, data representation and terminology for communication between personal telehealth devices and computers IEEE P11073-10400: Common Framework of communication, managing devices and allow vendors to access non-standard features. IEEE P11073-10404: Pulse Oximeters IEEE P11073-10406: Heart Rate Monitors IEEE P11073-10407: Blood Pressure Monitors IEEE P11073-10408: Thermometers IEEE P11073-10415: Weighing Scales IEEE P11073-10417: Glucose Meters IEEE P11073-20401: Point-of-Care Medical Device Communication Application Profile Common Networking Infrastructure, IEEE P11073-20601: Device Communication Application Profile Optimized Ex-change Protocol, which will define a common framework for creating an abstract model of personal health data

  49. IEEE 11073 family of standards Goal: interoperability with existing medical information systems Method: object-oriented modelling of functionality and areas of application (“Domain Information Model”)

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