MEG SUITE SAFETY RULES
Before Entering the Magnetically Shielded Room (MSR)
MSR Guidelines and Safety
Liquid Helium
Food and Beverage
Before Entering the Magnetically Shielded Room (MSR)
Subjects may not enter the MSR without signing a consent form. Anyone entering the MSR must first "de-metal" (empty pockets; remove jewelry, watches, wallets, beepers, hairclips; leave pens, clipboards etc. outside). Don't use paper clips or other small metal objects (staples, etc.) around the MSR; they tend to land on the floor and find their way inside the room.
MSR Guidelines and Safety
Protecting Vectorview from Magnetic Contamination
The Vectorview system is comprised of 306 thin-film superconducting interference devices (SQUIDs). The sensors are ultra-sensitive in that they can pick up changes in a magnetic field in the range of femtoteslas. Because of this sensitivity, the Vectorview is placed inside a MSR.
Although wearing metal objects while in the MSR is not harmful to the individual, bringing magnetic objects close to the Vectorview can cause trapped flux in the SQUIDs, which can lead to a long and expensive service break which would cause an obvious delay in measurements. Thus, before entering the MSR, we require that you remove any potentially magnetic objects. These include belts, keys, watches, coins, hair barrettes and pins, eyeglasses, and pieces of clothing with magnetic parts. Also, to prevent any magnetic dust from getting into the MSR, always remove your shoes before entering. Objects such as cell phones, pagers, cameras, flashlights, or any other electrical equipment are strictly forbidden. Never take a bar magnet inside the MSR.
When arranging for visitors or experimental subjects to come to the MEG lab, please inform them of these restrictions and see that they are appropriately prepared. Subjects who may arrive unprepared (eg, have magnetic parts on their clothing that cannot be removed) will be issued non-magnetic clothing supplied by the hospital.
If you do not know whether an object is magnetic or not, it is possible to test it inside the MSR. (However, please only do such a test in the presence of an experienced user or one of the techs). To test an object, one member of your group should wave the object inside the closed MSR while another member watches the raw data display. First wave your bare hands inside the helmet to be sure that you yourself are not magnetic. Next wave the object a few feet from the helmet, and if artefacts are not seen, then proceed to wave the object inside the helmet. If artefacts are seen on the raw data display, the object is magnetic and should not be brought inside the MSR.
Do not touch Vectorview unnecessarily, and keep a respectful distance from the device. Furthermore, to prevent microscopic magnetic particles from causing spurious results, do not attach anything (eg, tape) to the Vectorview helmet.
Do not leave any equipment in the MSR (other than screen, auditory and somatosensory stimulators, and response pads). Place experimental equipment instead in one of the cabinets outside the MSR, on the sink-side of the room. So that your equipment is not mispaced or borrowed, be sure to clearly label each item.
Moving the Vectorview Gantry
The gantry can be in one of two positions, upright (sitting down) or supine (lying down). The gantry is usually in the sitting position, but during the helium fill on Mondays, for example, the gantry is in the lying position. The gantry is lifted or lowered by pushing two buttons that are located on the back of the gantry. When these buttons are pushed, the gantry is lifted or lowered by ropes that are connected to a motor outside the MSR. During measurements, the gantry rests on two claws, both of which can hold at least four times the weight of the gantry. However, when the gantry is lifted or lowered, it hangs from the ropes only, and should something unexpected happen the whole unit (~270 kg) could fall down and seriously injure someone. Thus it is important to understand the following process to avoid such an injury.
There are four "traffic lights" behind the gantry that indicate whether or not it is safe to place a subject under the dewar. The green light indicates that the gantry is resting safely on the claws; you may place a subject under the dewar only when the green light is lit. The yellow light indicates that there is either tension in the ropes (eg, during lifting or lowering) or that the gantry is in an extreme position, where it shouldn't be. The red light indicates that something is wrong, and you should contact service personnel.
If you notice that the green light is not lit, and the subject is already seated under the dewar, first remove the subject and only afterwards should you move the gantry. Never move the gantry while the subject or the chair/bed is under the dewar!
Positioning the Subject Chair and Bed
The MEG chair is simply pushed into the opening beneath the dewar; no locking mechanism is needed. Similarly, the bed is pushed against Vectorview as well, but in order to keep it from moving the wheels should be locked.
Do not bring wheel chairs into the MSR. Instead, first place the subject on the bed outside of the MSR, and roll the bed inside the room.
Monitoring the Subject from Outside the MSR
During measurements, you can communicate with the subject by means of a two-way intercom system. Hit 1 to turn on the system, M to speak to the subject, and C to turn off the system. You will be able to hear the subject without pressing any additional buttons, although while you pressing M you will be unable to hear him or her. The microphone is quite sensitive, so you can keep it at about an arms-length when speaking to the subject. Additionally, you can monitor the subject by watching them on the TV monitor.
Never leave a subject or patient unsupervised in the MSR! If someone is inside the MSR and you are alone, do not leave the measurement room even for a short while. Someone must be available for help if the subject suddenly has an attack of illness, or if something unexpected happens.
Liquid Helium
Familiarize yourself with the section of the Vectorview manual that concerns the properties of liquid helium. It is highly unlikely that you would encounter such dangers while running a study due to the ventilation system installed in the MSR, however, it is important to keep these properties in mind while present for the helium fill, for example. Such properties include (1) its extremely low temperature when liquid (-279 C), (2) its ability to replace oxygen in the air, and (3) its tendency to expand in an explosive manner when transforming from liquid to gas at room temperature.
The cryogenic dewar of the Vectorview, which contains maximally 80 L of liquid helium, has several mechanisms to ensure that the dewar does not leak. However, if you hear any hissing sounds coming from the Vectorview, leave the MSR and contact Seppo Ahlfors or Valerie Carr.
Food and Beverage
No food is allowed inside the MEG lab. The cafeteria is located directly across from the lab, so please take your snack breaks at one of the tables in the café area. Beverages may be taken inside the lab (not the MSR, however!), so please be careful and keep trash to a minimum.
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