Dear Andreas,
the only way to run a cable into the scanner room is via a
filter plate, that usually consists of low-pass filters.
Any cable going into the scanner room on other routes,
including through the wave-guide, will introducd HF-noise
from outside. This will cause artifacts in your images or
spctra (consider the MR signal in the range of micro-volts).
Usually the scanner should have a few
spare filters. This was not the case for our scanner, where
we constructed a RF-tight insert for the wave guide, that
included an array of double-T filters. However, if you filter
your trigger signal to much, the slope might be too low to do
the trigger-job. Both, the hot line and the ground need to be
filtered.
Another way is to place an LED on the window(outside) and a
photodiode (inside).
Hope it helps,
Peter
On Thu, 3 Aug 2000, andreas joachim
bartsch wrote:
> Dear group members,
> I am bothered by a hf-artifact due to a trigger cable running into the
> scanner room. Any advice how to eliminate this, e.g. by what means of
> shielding?
> TIA-
> andreas
>
-----------------------------------------
Peter Erhard, Ph.D.
Nuklearmedizinische Klinik und Poliklinik
Klinikum rechts der Isar
Technische Universitaet Muenchen
Ismaninger Strasse 22
81675 Muenchen
Germany
Tel: 49-89-4140 4570
Fax: 49-89-4140 4938
[log in to unmask]
Laura, Marie & Peter Erhard
Josef-Dosch-Strasse 12
82131 Gauting
Germany
Tel: 49-89-8930 9424
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