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Elekta Neuromag Technical Manual

System hardware, revision f
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Elekta Neuromag
®
Elekta Neuromag
System Hardware
Technical manual
Revision F
September 2005

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  • Page 1 Elekta Neuromag ® Elekta Neuromag System Hardware Technical manual Revision F September 2005...
  • Page 2 Elekta Neuromag Oy. Elekta Neuromag Oy reserves the right to make changes in the specifications or data shown herein at any time without notice or obligation.

  • Page 3: Table Of Contents

    Contents List of symbols Chapter 1 Technical data 1.1. The probe unit ....................7 1.1.1. General ..................7 1.1.2. Sensors ..................7 1.1.3. Probe unit construction ............. 8 1.1.4. Dewar ..................8 1.2. Gantry, bed, and chair ..................9 1.2.1. Gantry ..................9 1.2.2.
  • Page 4 1.7. Data Acquisition System Hardware .............. 20 1.7.1. Real-time data acquisition computer system ......20 1.7.2. Stimulus I/O interface unit ............20 1.8. Computer system hardware ................. 21 1.9. Helium transfer equipment ................22 1.10. Environmental and power requirements, grounding ........22 1.11.

  • Page 5: List Of Symbols

    Magnetic objects and devices symbol. The use of these symbols in the vicinity of the probe unit indicate that magnetic objects or devices may cause disturbances in the operation of the system; they should therefore be avoided. See Elekta Neuromag System Hardware: User’s Manual Non-ionizing radiation, RF transmitter.
  • Page 6 NM20216A-F...

  • Page 7: Technical Data

    Technical data CHAPTER 1 1.1. The probe unit 1.1.1. General • Number of MEG channels: 306 channels • Sensor coverage: whole cortex, 1220 cm • Measurement positions: supine, upright • Minimum room height required: 2.3 m • Dimensions and weights: see chapter 2 1.1.2.

  • Page 8: Probe Unit Construction

    Technical data Noise performances for all operational channels are the following: • Gradiometer noise (white noise, 60Hz < f < 70Hz): max. 5 fT/(cm ) for 96% of channels, max. 10 fT/(cm ) for all gradiometer channels • Magnetometer noise (white noise, 60Hz < f < 70Hz): max. 5 fT/ for 96% of channels, max.

  • Page 9: Gantry, Bed, And Chair

    Technical data • Boiloff rate of liquid Helium: max. 8 liters per 24 hours • Exhaust of Helium gas due to liquid Helium boiloff (+20 °C, normal operation at atmospheric pressure): typ. 4 liters per minute • Helium transfer equipment: see 1.9 below •...

  • Page 10: Chair

    Technical data • Movement mechanism: Bed on wheels. Push/pull by hand. Wheels provided with locks. Upper part can be locked in place. • Removable head rest • Movement range of the upper bed: 300 mm • Dimensions and weights: see chapter 2. 1.2.3.

  • Page 11: Meg Preamplifiers

    Technical data 1.3.2. MEG preamplifiers • Preamplifiers for MEG channels inside the shielded room on top of the dewar • SQUID tuning: by an automatic program or manually • 12 channels on each preamplifier board, connected to a preamplifier motherboard on top of the Dewar top flange •...

  • Page 12: Electrode Interface

    Technical data • Test oscillator for testing the channels and for measuring the electrode impedances • Test oscillator frequency selectable at 20 Hz or 200 Hz • Test oscillator output amplitude selectable 100 mV or 1 mV (without load; with 1-MΩ signal terminators the signal coupled to the or 490 µV input of the channels is approximately 49 mV •...

  • Page 13: Filter Unit

    Technical data • Fully MEG-compatible • Bridging with EEG paste, skin preparation with liquid gel Electrode headbox: • 32 unipolar channels for single electrodes • Passive • Electrode sockets for reference electrode (REF) and ground driver (GND) • D37-connector for cable to electrode interface panel in gantry 1.3.5.

  • Page 14: Meg Main Electronics

    Technical data Other feedthrough RF filters • RF feedthrough filter for auxiliary electronics • Safety-isolating power supply for EEG front-end (see 1.4.2) • Lifting mechanism control unit and position indicator/ RF filter feedthrough unit 1.3.6. MEG main electronics • Principle: digital flux-locked feedback control loop realized with a digital signal processor (DSP) •...

  • Page 15: Eeg Main Electronics

    Technical data 1.3.7. EEG main electronics • Signal acquisition module (SAM) for 12 channels • one digital signal processor (DSP) per SAM • Resolution of A/D conversion: 16 bits • Type of coupling: dc • Input stage realized with instrumentation amplifiers with software controlled gain of 1 or 10, corresponding to SAM input ranges of ±10 V or ±1 V, respectively •...

  • Page 16: Front-End Eeg Power Supply (Isolated)

    Technical data 1.4.2. Front-end EEG power supply (isolated) • Input 24 V~ unregulated, supplied by the MEG preamplifier power supply • Output ±12.6 V, 60 W total • Applied part isolated with sector-wound transformer (24 V~/2 x 16 V~), dielectric strength > 4 kV (according to IEC60601-1, Class B) •...

  • Page 17: Main Iisolation Transformers

    Technical data • Location: inside main electronics cabinet, integrated to the VME subrack 1.4.5. Main iIsolation transformers • Number of units: 3 (MEG, Stimulus, 3D digitizer) • Primary: 100 / 115 / 120 / 200 / 230 / 240 V~ 50/60 Hz •...

  • Page 18: Auxiliary Electronics

    Technical data 1.6. Auxiliary electronics 1.6.1. Head Position Indicator (HPI) • Method: marker coils are attached to the head of the subject • Excitation: DSP-controlled current drive for each HPI-coil • Detection of signals: by sensor array • Number of coils: 3, 4, or 5 permanently attached to a connector. •...

  • Page 19: Liquid Helium Level Gauge And Display

    Technical data • Input ±10 V • Maximum load impedance: 100 Ω 1.6.5. Liquid Helium level gauge and display • Readout: remotely by real-time data acquisition computer or manually over local display • Probe active length (nominal): 55 cm • Probe resistance (nominal, at 300 K): 300 Ω •...

  • Page 20: Thermometer Sensors (For Maintenance Only)

    Technical data • Microphone input for voice intercom 1.6.8. Thermometer sensors (for maintenance only) • Number: 2 • Locations: lower end of helmet, upper end of wiring unit • Type: Pt-resistor • Nominal resistance at 273 K: 100 Ω 1.6.9. Voice intercom (option) •...

  • Page 21: Computer System Hardware

    Technical data • The units can be operated either in a mirroring mode duplicating the input/output at two physically separate places (16 lines total, default mode) or independently (32 lines total, optional) • Each channel individually selectable as input or output •...

  • Page 22: Helium Transfer Equipment

    60601-1 requirements fulfilled): 30%…75% RH, non-condensing • Relative humidity during storage and transport: 10%…95% RH, non- condensing. Special packaging instructions must be obeyed (available from Elekta Neuromag Oy). • Mains power voltage: 100/115/200/230/240 V~ ± 10 % • Mains frequency: 47…63 Hz...

  • Page 23: Classification (Iec 60601-1-1)

    Technical data Table 1. Power consumption of system units. The total consumption depends on system configuration. Unit Power [W] Appar. [VA] Notes Main electronics cabinet 1700/1900 1800/2000 64 ch EEG / 128 ch EEG Lifting unit 10/750 20/1200 Idle/working (20 s / run) 3-D digitizer Acq.

  • Page 24: Options

    Technical data 1.13. Options As an option, e.g., the following units may be included: • Two-way voice intercommunication system • CCTV video monitoring system • Audiovisual stimulus system • Back projection screen • Stimulus video projector • Chair insert for pediatric measurements •...

  • Page 25: Electromagnetic Compatibility (Emc)

    Such combination of the magnetically shielded room and the Elekta Neuro- ® system must be always be considered together as an entity.

  • Page 26: Guidance And Manufacturer's Declaration

    Technical data 1.14.3. Guidance and manufacturer’s declaration NOTE! The Elekta Neuromag MEG system should not be used adjacent to other systems, and if adjacent operation is necessary, the system should be observed to verify normal operation in the configuration in which it will be used.
  • Page 27 The Elekta Neuromag ® system is intended for use in electromagnetic environmen specified below. The ® customer or the user of the Elekta Neuromag system should assure that it is used in such an environment. Electromagnetic environment – Immunity test...
  • Page 28 If abnormal performance is observed, ® additional measures may be necessary, such as reorienting or relocating the Elekta Neuromag system Over the frequency range 150 kHz to 80 MHz, field strengths should be less than 3 V/m.
  • Page 29 The Elekta Neuromag ® system is intended for use in an electromagnetic environment in which radiated RF disturbances are controlled. The customer or the user of the Elekta Neuromag ® system can help prevent electromagnetic interference by maintaining a minimum distance between portable and mobile RF communications equipment (transmitters) and the Elekta Neuromag ®...

  • Page 30: Final Disposal

    The remaining material should be recycled where facilities and local regulations permit. Prior to disposal, always contact Elekta for advice. Where applicable, information will be available for treatment facilities and recyclers in accordance with Article 11 of directive 2002/96/EC of the European Parliament and of the Council of 27 January 2003 on waste electrical and electronic equipment (WEEE).

  • Page 31: Dimensions And Weights

    Dimensions and weights CHAPTER 2 2.1. Dewar dimensions 1080 Figure 2.1. Dewar side view. Dimensions in millimeters. NM20216A-F...
  • Page 32 Dimensions and weights Figure 2.2. Dewar front view. Dimensions in millimeters. NM20216A-F...

  • Page 33: Gantry And Chair Dimensions

    Dimensions and weights 2.2. Gantry and chair dimensions 1172 1813 1148 1206 Figure 2.3. Gantry in upright measurement position.Dimensions in millimeters. NM20216A-F...
  • Page 34 Dimensions and weights 1206 2000 Figure 2.4. Gantry in supine position..Dimensions in millimeters. NM20216A-F...

  • Page 35: Dimensions Of Cabinets

    2.3. Dimensions of cabinets 2040 Main electronics cabinet Stimulus cabinet Figure 2.5. Electronics and stimulus cabinet dimensions (in millimeters). For heights, see section 2.4. 1000 Adjustable: 100 (min.) 500 (max.) Figure 2.6. Filter cabinet dimensions. NM20216A-F...

  • Page 36: Table Of Dimensions And Weights

    Dimensions and weights 2.4. Table of dimensions and weights Unit W [cm] L/D [cm] H [ cm] Mass [kg] Measurement unit supine/upright 128/160 198/223 Patient’s bed (bed surface/maximum) 60/76 Patient’s chair Filter unit cabinet (adjustable) 150-190 Electronics cabinet Stimulus cabinet Acq.

  • Page 37: Chapter 3 Diagrams

    Diagrams CHAPTER 3 3.1. Electronics diagrams 3.1.1. System diagrams Main electronics cabinet Workstations Magnetically shielded room RF feedthrough Control MEG Preamp 2 fiber-optic links (MEG,EEG) Control Control digi- tizer Ethernet Digital signal proc. Opto- System bus isol. Subject SQUID Control Ethernet Digital Electrode...
  • Page 38 Diagrams Fiber-optic link Liquid Control Feedthrough Helium filter level display Stimulus E-net System Liquid triggers in/out Helium probe controller (Fiber-optic Analysis link) workstation E-net Head position LHe/HPI Feedthrough indicator Control Unit filter driver coils (5) E-net E-net SQUID SQUID Feedthrough SQUID Sensor Preamplifier...

  • Page 39: Eeg Electronics

    Diagrams 3.1.2. EEG electronics Filter unit Rf shield Isolated power feedthrough ±12 Vi 24 V~ 230 V~ Isolated gnd Preamplifier unit Osc+ Isolated Safety isolating RF feedthr. power supply transformer filter VME rack Osc– EEG control feedthr. ±15 V Control 230 V~ Non-isol.
  • Page 40 Diagrams Digital control (RS422), floating ±12 V EEG control feedthrough filter EEG preamplifier backplane Control signal (RS422) & ±15 V EEG preamplifier reference board 1/system EEG optoisolation / signal feedthrough filter 4 pcs, 16 channels/unit EEG preamplifier board 8 pcs, 8 channels/board EEG Ch 1–64 to Signal Acquistion Module Buffered reference,...

  • Page 41: Auxiliary Electronics

    Diagrams 3.1.3 Auxiliary electronics Feedthrough filter (MEG) Helium level probe/multiplexer 300 K 4.2 K Dc power Dc power Display I probe U probe sensor Tem- pera- (maintenance) ture gauge MEG control board Serial Control Dc power Aux board → Dipoles in Gantry MEG controller Phantom...

  • Page 42: Lifting Mechanism

    Diagrams 3.1.4 Lifting mechanism Fiber pair (green) (Upper limit= Tension no reflection, (yellow) light-on) (upper limit) Fiber pai r (Fibre 2, supine) (Tension= (tension) reflection, light-on) Limit (yellow) Control Fiber pair logic (Fibre 1, (Latch on= Upright) (latch) reflection, light-on) Fault (lowest pos.) Fiber pair...

  • Page 43: Electronics Cabinets

    Diagrams 3.2. Electronics cabinets 3.2.1. Main electronics cabinets Main MEG electronics rack MEG 192 ch Analog signals from / to MEG preamplifiers Main MEG electronics rack MEG 114 ch Analog signals from / to MEG preamplifiers Main EEG electronics rack EEG 64 / 128 ch Analog signals from EEG...
  • Page 44 Diagrams EMC filter Circuit breaker Main switch with power failure release [4 x] 230 V~ Mains sockets: from Roof fan isolation Ethernet switch transformer Auxiliary sockets From main [4 x] grounding point Mains sockets: Main DSP electronics Mains socket: RT computers Mains socket: Preamplifiers Figure 3.7b.

  • Page 45: Stimulus Cabinet

    Diagrams 3.2.2. Stimulus cabinet Stimulus cabinet Auxiliary feedthrough Signal feedthroughs Mains line RF filter Mains line power cable Grounding cable Figure 3.8. Stimulus cabinet, side view (side facing the magnetically shielded room) NM20216A-F...
  • Page 46 Diagrams BNC 3 – BNC 5 high-frequency BNC 1 – BNC 2 feedthroughs low-frequency feedthroughs XLR 3 XLR 1 – XLR 2 low-frequency low-frequency feedthrough feedthroughs Stimulus cabinet auxiliary feedthrough Figure 3.9.a Stimulus cabinet’s auxiliary signal feedthrough connectors. For specifications of the feedthrough filters, see 1.6.96. Figure 3.9.b Stimulus cabinet’s optional signal feedthrough connectors NM20216A-F...

  • Page 47: Power Supplies

    Diagrams 3.3. Power supplies 3.3.1. Schematic diagram Main electronics cabinet Filter unit 5V 4A 230V~ +6V 1.2A –6V 1.6 A +Vca –Vca Gc ±15V 0.8A –Vc Main electronics power supply unit (9 pcs/11 pcs) MEG electronics front end power ±15V 9A Mains switch 240V~ 230V~...

  • Page 48: Recommended Power And Grounding Arrangement

    Diagrams 3.3.2. Recommended power and grounding arrangement Sockets for workstations and other equipment (min. 10) System grounding point Filter Unit Grounding terminal in the Magnetically shielded room 100/115/120/ transformer room 230V 200/230/240 V RF Filter Sockets Harmonic filter Main electronics cabinet RF Filter Sockets Socket for...

  • Page 49: Probe Unit

    Diagrams 3.4. Probe unit 3.4.1. Gradiometer chip and sensor array Detector array, right frontal view Detector array, side view. Detector array, top view Average distance between sensor elements: 34,6. Figure 3.12.a Sensor array. Dimensions in millimeters. Figure 3.12.b Triple sensor element chip. NM20216A-F...

  • Page 50: Cryogenic Insert

    Diagrams 3.4.2. Cryogenic insert Figure 3.13. Cross-section of the Dewar (see also Fig. 3.14). top flange neck-plug wiring unit flexible cable assembly support tube printed circuit board Figure 3.14. Close-up of the insert inside the Dewar (see also Fig. 3.13). NM20216A-F...

  • Page 51: Data Acquisition Software Block Diagram

    Diagrams 3.6. Data acquisition software block diagram Data Acquisition System Software Structure Acquisition Workstation Network, TCP/IP Real-Time Data Acq.Computers sinuhe connections kaptah1 .. kaptah4 Acquisition Online average Data control megacq response display xplotter Acquisition server Head Position Indicator collector Online saver Control averager...

  • Page 53: Appendix

    Appendix Additional site-specific data sheets (if applicable) NM20216A-F...
  • Page 54 Elekta Neuromag Oy P.O. Box 68 FIN-00511 Helsinki, Finland Tel: +358 9 756 2400 Fax: +358 9 756 24011 E-mail: neuromag@neuromag.fi Web: www.neuromag.com...

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