Biomedical Engineering Reference
In-Depth Information
Fig. 3.55.
A cut-away diagram of the horizontal dewar made using a “ship-in-a-
bottle” technique
surface of the dewar where the subject's/patient's head touches. Figure 3.55
shows a cut-away diagram of this dewar. The helmet-shaped manifold is the
sensor-holder, with many sockets for the gradiometers.
One of the merits of the horizontal dewar is that a small room is sucient
for installation because of the low height (0.89 m) of the dewar. The size of
the MSR can be reduced to a 2.4 m height by 2.2 m width by 3.5 m depth
(outer shell dimensions). Two systems in Boston and Tokyo are installed in
this size of MSR. The next merit is that the dewar is gantry free. The dewar
is placed on a rigid base, therefore eliminating numerous concerns caused by
moving mechanisms.
The third merit is that the patients can be measured in a relaxed lying
position. The subject's MEG responses are measured for 10-20 minutes, and
they are required to stay still during measurement. Therefore, it is necessary
to provide a relaxing and easy position for the subject. Our solution with the
horizontal dewar is a bed on which the patient can recline in a supine mode,
with his or her head resting on a pillow. The bed is slid towards the dewar so
that the head is placed into the concave part of the dewar. For the patient, it
is easy to be transferred from the stretcher to the bed. The lying position is a
goodmatchwithotherscanners,suchasMRIandX-rayCT,whichmeasure
patients in the same way. We made a vertical type of dewar with the “ship-
in-a-bottle approach” in order to compare the vibration of the subject's head
during the MEG measurement. To confirm the improvement, the vibration
