Elekta Neuromag® Site Planning Guide for MaxShield - Psychology

Elekta Neuromag
Elekta Neuromag ®
Site Planning Guide for
MaxShield
June 2006
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NOTICE
This document contains copyrighted and possibly confidential
information and is intended for the exclusive use of customers
having Elekta Neuromag products and authorized representatives
of Elekta Neuromag Oy. Disclosure to others or other use is
strictly prohibited without the express written authorization of
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. Elekta Neuromag Oy denies any responsibility for
damage to apparatus or persons due to improper use or service
performed by unauthorized persons. Elekta Neuromag Oy assumes
no liability for damage and/or failure of equipment caused
by faulty site preparation.
REVISION HISTORY
- 15.11.2004 Preliminary draft edition
- 30.6.2006 First release (final draft for review)
© Copyright Elekta Neuromag Oy, Helsinki, Finland
Printed in Finland.
All rights reserved. Reproduction in any form without the written
permission of Elekta Neuromag Oy is strictly prohibited.
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1
CONTENTS
1. MAGNETIC REQUIREMENTS ............................................................................... 5
1.1. Sources of magnetic interference...................................................... 5
1.2. Measurement of magnetic interference ............................................. 5
1.3. Residual magnetic field inside the magnetically shielded room ........... 6
2. MAXSHIELD MAGNETICALLY SHIELDED ROOM CHARACTERISTICS ......................... 8
2.1. Dimensions .................................................................................... 8
2.2. Feedthroughs ................................................................................. 8
2.3. Door .............................................................................................. 9
2.4. Inside / outside décor , lights, and accessories ................................... 9
3. CLIMATIC REQUIREMENTS ............................................................................... 10
3.1. Room temperature in the shielded room, equipment area and operator
area ............................................................................................. 10
3.2. Relative humidity in the shielded room, equipment area and operator
area ............................................................................................. 11
4. POWER SUPPLY AND GROUNDING REQUIREMENTS ............................................ 12
4.1. Power Requirements ..................................................................... 12
4.2. Connection to the building’s power lines, power requirements .......... 13
4.3. Grounding .................................................................................... 14
5. VIBRATION CONSIDERATIONS.......................................................................... 15
5.1. General Recommendations ............................................................ 15
5.2. Recommendations for allowable vibration ...................................... 15
5.3. Measurement of vibration.............................................................. 16
6. BUILDING REQUIREMENTS .............................................................................. 17
6.1. Floor space requirements and layout considerations ........................ 17
6.2. Load distribution .......................................................................... 20
6.3. Free ceiling height requirements .................................................... 21
6.3. Exhaust vents................................................................................ 21
6.4. Transportation and access during installation .................................. 21
6.5. Dimensions of the main components of the MEG system ................... 22
6.6. Other considerations ..................................................................... 22
7. TELECOMMUNICATION FACILITIES ON SITE ........................................................ 23
APPENDIX............................................................................................................. 24
MEG-MRI layout considerations ...................................................... 24
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Elekta Neuromag® Site Planning Guide for MaxShield
1
1. MAGNETIC REQUIREMENTS
1.1. Sources of magnetic interference
1.2. Measurement of magnetic interference
A site survey must be conducted to define the location of the
Elekta Neuromag® system. The goal is to find an environment in
which the magnetic disturbances are at a level low enough to be
effectively compensated for by the shielded room and the active
compensation systems.
Obvious sources of magnetic interference are elevators, electrical
transformers, power cables, mechanical/plant rooms, cars, parking
lots, subways, subway stations, trains, street cars, MRI and
CT scanners, and linear accelerators. Elekta should be contacted
if any doubt exists regarding the effects of magnetic interference
sources.
Large volume/area ferromagnetic objects, e.g. steel-covered doors,
walls, floors, and furniture should not be located in the vicinity of
the shielded room because they may intensify the interference fields
and cause movement artefacts. If in doubt, contact Elekta.
Magnetic interference can also be generated by mechanical vibrations
if the sensors move in the remanent field inside the room.
For detailed discussion see Chapter 5.
The level of magnetic interference is defined by measuring at
different times of the day the three components of the ambient
magnetic field (= B amb
) as functions of time, and calculating the
corresponding spectra. A three-head flux gate connected to a
spectrum analyzer is used for this purpose. The measurement is
carried out by Elekta or by an employee of a vendor of magnetically
shielded rooms.
If an MRI or CT unit or related equipment (see 1.1. above) is in close
vicinity of the measurement point, the measurements should be
carried out both with the equipment on and with the equipment off.
For measurement of vibration, see Chapter 5.
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1 Magnetic requirements Elekta Neuromag® Site Planning Guide for MaxShield
1.3. Residual magnetic field inside the magnetically shielded room
The spectral density of the residual magnetic field B res
inside the
shield is calculated in the following way:
B res
= B amb
(f)/S(f),
where
B amb
(f) = the spectral density of the ambient magnetic field
at frequency f (from the site survey). Usually, all
three orthogonal directions are treated separately.
It is also common to consider the vector sum of
the x-, y-, and z-components.
S(f) = the combined attenuation factor of the
magnetically shielded room (MSR) and active
compensation systems at frequency f. Note: in
general, the shielding factor depends also on the
location inside the room and on the direction. For
simplicity, however, an average value of all
directions in the middle of the room is often used.
At DC, the state of static magnetization of the shielded room
normally determines the remanent DC-field B rem
in the room. In
such a case the remanent field can be reduced by proper demagnetization.
To obtain optimum performance of the magnetometer channels,
the value of B amb
, as a function of frequency, and the spectral
density of the remanent DC-field B rem
should not exceed the
following values:
Ambient magnetic field outside, Spectral density:
B amb
≤ 100 nT/ Hz at 0.1 Hz
B amb
≤ 10 nT/ Hz at 1 Hz
B amb
≤ 1 nT/ Hz above 10 Hz
Remanent DC-field inside:
B rem
≤ 50 nT
During MEG-measurements, the magnetometer channels must
not saturate. The residual peak-to-peak fluctuation B res
(0) p-p
at
very low frequencies is given by
B res
(0) p-p
= B amb
(0) p-p
/S(0),
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Elekta Neuromag® Site Planning Guide for MaxShield Magnetic requirements 1 1
where
B amb
(0) p-p
= the p-p fluctuation of the ambient field at very low
frequencies as determined from at least 30 min long
DC-coupled recordings during site survey, and
S(0) = the low frequency limiting value of S(f).
To guarantee operation, B amb
(0) p-p
should not exceed
P-P range of ambient field:
B amb
(0) p-p
≤ 2 µT
If the above limits are exceeded, additional shielding might be
necessary.
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Elekta Neuromag® Site Planning Guide for MaxShield
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2. MAXSHIELD MAGNETICALLY SHIELDED ROOM CHARACTERISTICS
2.1. Dimensions
2.2. Feedthroughs
External floor space:
External height:
Door opening:
Door swing radius:
3.2 m × 4.2 m (without exterior finish)
2.6 m
1.0 m × 2.0 m
1.3 m
The following 6 holes for technical feedthroughs are required for
the basic system:
• 2 × φ85 mm for filter unit (feedthrough type A)
• φ85 mm for stimulus cabinet (feedthrough type A)
• φ35 mm for measurement unit movement control (feedthrough
type B)
• φ35 mm for helium boil-off (feedthrough type B)
• φ100 for helium safety vent (feedthrough type C)
Additional holes :
• φ100 mm feedthrough for visual stimulus projector, center
height 1000 mm above MSR inner floor (feedthrough type
D). The visual stimulus projector is available as an option.
• φ60 mm feedthrough for the optional intercom loudspeaker
(feedthrough type E)
.• φ35 mm hole for the optional CCTV camera (feedthrough
type B)
• Two φ120 mm holes / rectangular openings for ventilation
(feedthrough type F)
• φ35 mm hole for the lighting
• One or two φ50 mm additional feedthroughs can be optionally
provided for medical gases and patient monitoring devices
such as a pulse oximeter. Alternatively, these feedthroughs
can be fitted to the stimulus cabinet.
The optimum hole locations vary according to the site. For
details, contact Elekta representative, see also Section 6.1.
User-supplied TV monitoring (CCTV) systems are not recommended
to avoid RF-leakage via the camera and its cables.
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Elekta Neuromag® Site Planning Guide for MaxShield MaxShield shielded droom 1 2
2.3. Door
Doorstep:
0.13 m. A ramp (approx. 1 m length, slope < 10°) is provided to
ensure easy access for both the subjects during MEG-measurements
and for the LHe storage container during a re-fill operation.
Door mechanism:
2.4. Inside / outside décor , lights, and accessories
Mechanical, can be manually opened both from inside and
outside. The door is provided with a stopper to limit the opening
to approximately 90°. For possible door locations, see Sect. 6.1.
Inside wall coverage
Provided with light, sound-absorbing and electrically insulating
material.
Outside wall coverage
Outside coverage is not provided as standard part as it normally
needs to be matched with the style and look of the surroundings.
A dry-wall made of light electrically insulating material and built
on site after shielded room installation is recommended. The
outside coverage must not be attached to the shielded room wall.
Inside floor
Provided with easy to clean laminate resistent to eventual minor
leakage of condensation water from the He-cooled pipes inside
the gantry.
Loads on ceiling and walls
Additional load to unsupported magnetic shield material must
not be applied. Light objects can be attached to inside décor.
Interior lighting
Adjustable and dimmable halogen spots (DC operated)
Accessories
All accessories brought inside the room should be of nonmagnetic
material. Large metallic conducting objects (area > 0.25 m 2 ) must
be avoided.
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Elekta Neuromag® Site Planning Guide for MaxShield
3
3. CLIMATIC REQUIREMENTS
Maintaining the specified environmental conditions is essential
to ensure the stable functioning of the system. Note that the
relative humidity requirements have to be taken into account
simultaneously with the temperature.
NOTE:
During transportation and storage, the temperature of the Elekta
Neuromag MEG system must be between 0 – 40 ºC, and the
relative humidity between 10 – 95 %, non-condensing.
3.1. Room temperature in the shielded room, equipment area and operator area
Excessively high room temperatures may cause overheating of
the power components thus reducing component lifetimes.
Requirement for the ambient temperature outside the shielded
room including the equipment area and the operator area:
T amb
= 20 – 24 ºC.
Approximate heat load in the equipment area is 2 kW and in the
operator area 3 kW (not including stimulators). Exact heat load
depends on system configuration. Refer to Section 4 for more
information on power consumption.
Requirement for the air temperature inside the shielded room:
T MSR
= 20 – 28 ºC.
Approximate heat load due to electronics inside the shielded
room is 0.3 kW. Addtional heat is generated by the lights (0.2 kW
at full brightness) and persons inside (0.1 kW per person). The
heat transfer through the MSR wall depends on the wall covering,
which effectively acts as thermal insulation. Therefore, ventilation
in the room should be designed to carry the heat away.
NOTE:
To maintain the temperature inside the shielded room below 28 ºC,
cooling of the input air may be needed. The minimum capacity of
the air input 30 liters/s, corresponding to temperature difference
of 8 °C.
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Elekta Neuromag® Site Planning Guide for MaxShield Climatic requirements 1 3
3.2. Relative humidity in the shielded room, equipment area and operator area
Excessive air humidity promotes oxidation of metals, can be
detrimental to electric circuits and computers and increase leakage
currents as well as may cause water to condense on the cold
parts of the system. Low humidity in turn increases static electricity,
which can interfere with the SQUID detectors and damage
electronic circuits. It also causes discomfort to the users.
Relative humidity limits:
RH = 40% – 70%.
To maintain the humidity within limits, humidification/dehumidication
systems are normally necessary. Natural air humidity
can vary substantially depending on local climate, from 10 % to
over 90 %.
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Elekta Neuromag® Site Planning Guide for MaxShield
4
4. POWER SUPPLY AND GROUNDING REQUIREMENTS
4.1. Power Requirements
The power requirements of the system units are listed in Table 1.
The applicable standard line voltages (RMS) are: 100, 115, 120,
200, 215, 220, 230, and 240 V. The recommended voltages are 200,
230, and 240 V. The nominal line frequency should be 50 or 60 Hz.
Table 1. Power consumption of system units.
The total consumption depends on system configuration.
U nit
P ower [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
40
60
Acq.
workstation, 2 TFT monitors (typ.) 400
Anal.
workstation, 2 TFT monitors (typ.) 400
Trigger
I/O unit (2 pcs, total)
20
Voice
intercom (typ.)
10
CCTV video monitoring (typ.)
50
Finger
response pad
10
DAT drive (typ.)
100
MOD drive (typ.)
100
Color
printer (typ.)
250
/1650
Norm./max.
Monochrome
printer (typ.)
30/600
Idle/printing
Video
projector (typ.)
800
Electrical
stimulator (typ.)
10
Audiovisual
stimulus system (typ.)
200
Feed-forward
active compensation
200
Shielded
room lights
200
Note 1
Note 2
Stimulus cabinet not included as a unit since the consumption depends on the equipment used. Max 10 A.
Ratings marked with "typ." are representative values only, actual values depend on the exact model used
NOTE: Power requirements for lighting outside the shielded
room, air conditioning, and general purpose outlets are not
included.
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Elekta Neuromag® Site Planning Guide for MaxShield Power supply and grounding 1 4
4.2. Connection to the building’s power lines, power requirements
Separate power lines from the building’s main transformer and
system isolation transformers are required, see Fig. 1. The isolation
transformers (T 1
and T 2
) are provided by Elekta. They comply
with the medical standards EN 60601-1 and EN 61558-2-15
EN60742). The distance of the isolation transformers from the
shielded room should normally be more than 3 m. For details,
contact Elekta.
At sites where the mains voltage is less than 230 V~ the lifting unit
is connected to main using a portable step-up transformer provided
with the system (plug connection).
Power lines etc. cabling carrying substantial currents, power
supplies, fluorescent lamps or other electric equipment should
not be mounted on the shielded room walls or directly above the
shielded room roof.
MAINS
L
N
PE
S1
S2
F1
L
N
PE
L
N
PE
Sockets for
workstations and
other equipment
(min. 10)
System grounding point
Filter Unit
Grounding terminal in the
transformer room
S3
100/115/120/
200/230/240 V 230V
T1
F2 L
N
L1
0
L2
F3
S4
F4
Magnetically shielded room
RF Filter Sockets
L1
S7
L2
PE
S5
0 S6
N
F7
L = mains live
L2
N = mains neutral
PE = protective earth (ground)
L1 and L2 = isolated power terminals (symmetiric with respect to ground)
Switches S7 and S8 are inside cabinets (max. 10A), supplied by Elekta
Secondary fuses (F3,F4,F6, F7) and switches (S4, S6) are optional
F5
L
1:1
T2
L1
F6
Main electronics cabinet
RF Filter Sockets
L1
S8
L2
PE
Stimulus cabinet
Figure 1. Connection to building’s power lines and grounding
arrangements. The isolation transformers (T1–T2) and
components inside cabniets are provided by Elekta.
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4 Power supply and grounding Elekta Neuromag® Site Planning Guide for MaxShield
4.3. Grounding
Proper grounding is essential in order to maintain shielding
integrity. The guidelines listed below must be carefully followed.
The magnetically shielded room (MSR) is grounded at one point
only using a separate grounding cable connected to the common
grounding terminal of the building transformer providing power
to the Elekta Neuromag® system. The grounding cable should
have a cross-section of 50 mm 2 or larger and it should be stranded
(preferably fine-stranded) to ensure low inductance path to ground.
The wire is connected to the M8 grounding bolt at the feedthrough
filter unit during installation of the MEG system. The connection
must be made in such a way that it can be disconnected when the
isolation of the magnetically shielded room is measured. The
isolation resistance between the disconneted shielded room and
the end of the grounding cable must be more than 1 kΩ. The walls
of the MSR must be electrically isolated from all building parts
including the air conditioning ducts and helium exhaust pipes.
All components of the electronics must be grounded to the same
single point as the magnetically shielded room, see Figure 1.
NOTE:
A dedicated grounding electrode separate from the grounding
terminal of the building transformer can be used but is not
recommended.
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Elekta Neuromag® Site Planning Guide for MaxShield
5
5. VIBRATION CONSIDERATIONS
5.1. General Recommendations
Generally, the magnetically shielded room should be located at
a place where low frequency vibrations are as small as possible.
Thus, basements are preferred to upper floors.
NOTE:
Spring type suspension designs of the room are not recommended
since they may cause low frequency oscillation.
5.2. Recommendations for allowable vibration
Magnetic interference signals due to mechanical vibrations are
generated by the relative motion of the magnetic sensors with
respect to the remanent field inside the room. A typical value of
remanent field is ≤ 50 nT (see chapter 2.1.1). The magnetometers
are more sensitive to the vibration than the gradiometers.
General criteria for maximum allowable vibration observed in a
site survey are difficult to define in practice. Vibration artefacts
have often prominent peaks and if they happen to match with
natural structural resonances of the room, the effect of building
floor vibration may be augmented. Moreover, air pressure variations
e.g. caused by ventilation can produce vibration artifacts.
Magnetic artefact caused by vibration as such are relatively
uniform and is thus they are effectively reduced by software noise
reduction based on spatial filtering like signal space projection
and MaxFilter.
The spectral density of the magnetic interference signal B vibr
in a
magnetometer channel due vibration is given by
B vibr
(f) ≤ X(f) B rem
/ L 1
,
where
X(f) = displacement spectrum of the magnetometer in the
units of m/ Hz
B rem
L 1
= remanent field inside the MSR (≤ 50 nT)
= Characteristic length associated with the first
gradient of the remanent magnetic field, typically
L 1
= 10 m.
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5 Vibration considerations Elekta Neuromag® Site Planning Guide for MaxShield
5.3. Measurement of vibration
The following conservative recommendations for the spectral
density of the displacement spectrum at the site of the shielded
room X amb
are based on an assumption that disturbance due to
vibrations is not seen in the magnetometer output spectrum when
noise reduction techniques are not used.
Displacement, Spectral Density (conservative recommendation)
X amb
≤ 20 µm/ Hz at 0.1 to 1 Hz
X amb
≤ 2 µm/ Hz at 1 to 10Hz
X amb
≤ 1 µm/ Hz above 10 Hz
In case the readout of the vibration analyzer is in units of velocity,
V amb
, the corresponding criteria are:
Velocity, Spectral Density (conservative recommendation)
V amb
≤ 12 (µm/s)/ Hz at 0.1 to 1 Hz
V amb
≤ 12 (µm/s)/ Hz at 1 to 10Hz
V amb
≤ 60 (µm/s)/ Hz ) at 10 Hz
With proper signal-space noise reduction or by application of
MaxFilter these values can be relaxed considerably. Thus
exceeding these limits, especially only at certain frequencies, is
not necessarily detrimental.
The level of vibration is defined by measuring at different times
of the day the displacement or velocity as functions of time, and
calculating the corresponding spectra. If obvious sources of vibrational
interference are in close vicinity of the measurement point, the
measurements should be carried out both with the equipment on and
with the equipment off.
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Elekta Neuromag® Site Planning Guide for MaxShield
6
6. BUILDING REQUIREMENTS
6.1. Floor space requirements and layout considerations
The minimum floor space requirement for the complete system
is about 40 m 2 . Anyhow, it is recommended, if possible, to
reserve an area of 60–70 m 2 to ensure optimal conditions to
operate the system from both operator’s and patient’s/subject’s
point of view. Examples of site layouts are shown in Figs. 2 and
3. For other possibilities, contact Elekta representative. See also
discussion below.
Outer dimensions of a MaxShield shielded room are given in
chapter 2. The exact dimension will depend on the exterior
finish.
9000
Isolation
transformers
Storage for
liquid Helium
etc.
Printer
Analysis
PC
MEG Equipment area
Electr.
cabinet
Feedthrough
Lifting
unit
filter
1500
PC
Acquisition
Stimulus control
Stimulus
cabinet
6500
Ramp
HPI chair
Patient preparation
and head digitization
MSR
equipment
area
Video
projector
Figure 2. Example layout of a large Elekta Neuromag® site. The
office furniture, PCs, peripherals, stimulation equipment, and
liquid Helium containers shown for illustrational purposes in the
figure are not part of the standard system. Another example
layout for a smaller site is shown in Fig. 3.
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6 Building requirements Elekta Neuromag® Site Planning Guide for MaxShield
The door can be either on the shorter or on the longer side in any
corner, subject to the following constraints:
• distance from nearest outside corner to free opening is approx.
0.5 m, depending on exterior finish thickness (see Fig.
4)
• handedness of the door is selectable
• the door opening should be as far from the sensor unit as
possible.
• there should be enough space in front of the shielded room
door for the door to open, to position the ramp and transfer
in and out the bed, chair, and and helium storage vessels etc.
The electronics is preferably located at the shorter side of the
room behind the sensor unit. If space does not permit, alternative
locations are possible as illustrated in Fig. 5. The following
constraints must, however, be met:
• free access to the the feedthrough filter unit is needed from all
three sides not facing the shielded room wall (min. 0.3 m
space)
• both front and back doors of the main electronics cabinet
need to be accessed and opened
7000
Analysis
Printer
MEG Equipment area
Electr.
cabinet
Feedthrough
filter
Lifting
unit
1500
Isolation
transformers
Stimulus control
Acquisition
Stimulus
cabinet
6500
Ramp
Patient preparation
and head digitization
HPI chair
Storage for
liquid Helium
etc.
Video
projector
Figure 3. Example layout for a small Elekta Neuromag® site.
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Elekta Neuromag® Site Planning Guide for MaxShield Building requirements 1 6
0.5 m
0.5 m
Figure 4. Possible door locations. For further details, see text.
800
Feedthrough
filter
Lifting unit
500
Lifting unit
Electr.
cabinet
Electr.
cabinet
Feedthrough
filter
Stimulus
cabinet
Stimulus
cabinet
Video
projector
Video
projector
VARIANT A
VARIANT B
Figure 5. Examples of alternative electronics locations. For further
details, see text.
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6 Building requirements Elekta Neuromag® Site Planning Guide for MaxShield
6.2. Load distribution
• main electronics cabinet and feedthrough filter unit must be
adjacent due to cable length restriction
• exact feedthrough hole locations are subject to constraints
due to support structures of the room. Feedthrough filter unit
is centered with respect to the signal feedthrough holes
• the lifting unit must be near the room corner in order to avoid
too steep curves of the Bowden cable transmitting the movement
• the cabinets and the lifting unit are not symmetric
The MaxShield shielded room can even be directly located
against a wall at two sides. Such configuration may, however,
require special arrangements.
An adequate space for liquid Helium storage container must be
reserved. An easy access from the storage area to the shielded
room should be ensured as well. The diameter of a typical 100-
liter storage Dewar is 0.6–0.7 m and height 1.3–1.5 m.
It is advisable to have an area for changing clothes and for waiting
available in the near vivinity (not necessarily adjacent ot the MEG
equipment area.
Head digitization station should be near the data acquisition
workstation or a dedicated additional terminal (PC). The analysis
workstation does not need to have to be in the same area as the
acquisition but it can also be remotely located.
The total weight of the MaxShield shielded room with the
system inside is typically 5000 kg. The weight is distributed
approximately as follows:
• Room floor and measurement unit: 1500 kg distributed
evenly over the room area (12 m 2 )
• Room walls and roof: 3500 kg distributed evenly on a 70 mm
wide edge around the room area
The room may be assembled on an underlayment (e.g. plywood)
to distribute the load more evenly. In addition, the electronics
cabinets need to be taken into account as approximately pointlike
loads. For details, see Table 2.
Conventionally, the load is expressed as the intensity of distributed
load (average floor load). It is determined by calculating the
intensity of a load evenly distributed over the whole external floor
base plate which results in equal maximum deflection or maxi-
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Elekta Neuromag® Site Planning Guide for MaxShield Building requirements 1 6
6.3. Free ceiling height requirements
6.3. Exhaust vents
6.4. Transportation and access during installation
mum principal bending moment as the load under investigation.
Generally, the simple calculation of dividing the shielded room
total mass by the shielded room area gives a too high value; for
proper determination the base plate properties need to be taken
into account.
The room can optionally be secured to the floor if required by
local regulations (e.g. as a precaution for earthquakes).
The installation of the MaxShield shielded room requires a
clearance of 50 mm above the room exterior height.
A free height of 1.50 m above the top opening of the liquid He
storage containers should be available in the vicinity of the
shielded room for the insertion of the LHe transfer siphon. If a
siphon extention is used the length of the extension (0.22 m for the
standard extension) should be added. The minimum area for this
height is 1 m 2 . In operator area and equipment area there are no
other special requirements.
Provision must be made for a φ100 mm safety exhaust duct
directly to the outside of the building.
An area to unload the crates and an adequate access to the
unloading area and from unloading area to the site must be
provided during the installation of the system. The access route
should not contain steps as many components are so heavy that
forklifts (pallet jacks) must be used. Any door openings, corridors
etc. should be wide and high enough that the crates and unloaded
components can be transferred.
All crates are to be transported in their original orientation whilst
the components can be carried in any orientation (vertical/horisontal)
which is convenient for access. The only exception is the
MEG measurement unit which must always be kept in vertical
orientation. Thus, a minimum height clearance of 2.00 m is
required all the way, including all door openings.
The largest crates for the LMSR are 3.2 m × 0.9 m × 0.9 m, 2.6 m
× 1.8 m × 0.7 m, and 5.0 m × 0.3 m × 0.3 m, 7 crates total.
Correspondingly, the largest crates for MEG components are 1.6
m × 1.2 m × 2.3 m and 2.5 m × 0.9 m × 1.1 m (LxWxH), 7 crates
total.
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6 Building requirements Elekta Neuromag® Site Planning Guide for MaxShield
Largest single shielded room elements that need to be transported
from the unloading area to site are 1.6 m × 0.3 m × 2.3 m and 2.4
m × 0.6 m × 0.1 m, and largest MEG components are 1.0 m x 1.3
m x 2.0 m and 0.6 m × 0.8 m × 2.1 m.
6.5. Dimensions of the main components of the MEG system
6.6. Other considerations
The dimensions of the main components of the system are listed
in Table 2.
A water faucet and sink is recommended in the patient preparation
are.
When designing the MEG area local regulations must be taken
into account. These may include building, electrical and HVAC
regulations as well as and possible requirements for hospital
environment and occupational health.
A smoke detector should be installed in the ventilation exhaust
duct to monitor the inside of the shielded room. Installation of a
fire detector inside the room is not recommended to prevent RF
leakage through the detector cabling.
Table 2. The dimensions of the components of the Elekta
Neuromag® system.
Unit
Width
(cm)
Depth
(cm)
Height
(cm)
Weight
(kg)
Measurement
unit (supine/upright) 96
128/160
198/223
350
Patient
bed (bed surface/maximum) 75
230
60/76
75
Patient
chair
70
135
78
80
Filter
unit (adjustable height)
100
40
150-190
150
MEG electronics cabinet
60
80
212
250
Stimulus
electronics cabinet
60
80
202
100
Data
acquisition workstation (min./typ.) 44/70
57/75
68
25
Data
analysis workstation (min./typ.) 44/70
57/75
68
20
Monitors
(typical 19" TFT, four pcs.) 41
20
46
4 x 9
Gantry
lifting unit
37
64
37
30
HPI
chair + digitizing unit
54
56
98
10
Back-projection
screen
118
33/
6 186
35
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Elekta Neuromag® Site Planning Guide for MaxShield
7
7. TELECOMMUNICATION FACILITIES ON SITE
For software installation and upgrades, possible troubleshooting,
and maintenance, the site should be equipped with a remote
access over tcp/ip -connection or with an ISDN line. Proper data
security precautions such as dedicated firewall setups etc. should,
however, be implemented.The data connection is needed already
during the installation, as well as an ordinary telephone line.
Computers of the MEG system are connected to ethernet network
with twisted pair (UTP, CAT 5) cable. The cabling and
location for network switch should be ready before the installation
starts. For best performance the network should be a separate
subnet. Following information is needed for installation: the
intended IP addresses of all devices, the network mask, the IP
address of the gateway to external networks, the domain name
and the IP address of the domain name server.
If an official registered network is unavailable, the network
addresses can be selected from non-routed internal network
addresses. For details contact Elekta.
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Elekta Neuromag® Site Planning Guide for MaxShield
A
APPENDIX
MEG-MRI layout considerations
The following discussion illustrates the issues that have to be
taken into account when locating the MEG unit and an MRI unit
close to each other.
In an ideal situation the axis of the bore of the MRI unit should
be parallel to the longer wall of the shielded room of the MEG
unit. Additionally, the electronics cabinets of the MRI device
should be as far away from the MEG unit as possible, as shown
in Figs. A1 and A2. The purpose of these arrangements is to
minimize, inside the magnetically shielded room, the effect of fast
switching electromagnetic pulses of the MRI unit that are due to
the gradient amplifiers. The permanent magnetic field generated
by the MRI is not considered harmful to the operations of the
MEG unit as long as we are beyond the 50-mT (0.5 G) line.
Equipment area
of the MEG unit
RF-shield
Magnetically
shielded room
MEG
MRI
Equipment area
of the MRI unit
Recommended minimum distance 10 meters
Figure A1. The axis of the bore of t he MRI unit should preferably
be parallel to the longer wall of the magnetically shielded room.
If this is not possible, an alternative layout is shown in Fig. A2. It
is recommended to locate the equipment area of the MRI unit as
far away from the magnetically shielded room as possible.
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Elekta Neuromag® Site Planning Guide for MaxShield Appendix 1 A
Equipment area
of the MEG unit
Magnetically
shielded room
MEG
Recommended minimum distance 10 meters
MRI
RF-shield
Equipment area
of the MRI unit
Recommended minimum distance 10 meters
Figure A2. Recommended layout if the axis of the MRI unit is not
parallel to the longer wall of the magnetically shielded room. As
in the previous layout above it is recommended to locate the
equipment area of the MRI unit as far away from the magnetically
shielded room as possible.
NM21643A 25

Elekta Neuromag Oy
P.O. Box 68
FIN-00511 Helsinki, Finland
Tel: +358 9 756 2400
Fax: +358 9 756 24011
E-mail: neuromag@elekta.com
Web: www.elekta.com