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ERT Module
Temperature probes are fragile and should be handled with care. The tip of the probe
can be broken or cracked if the tip is bent. Problems with the temperature probe can
occur if it develops a crack. Since the thermister in the tip of the probe operates at 5 V
and a break lets conductive fluid from the animal make contact with the thermister wire,
a small offset voltage can occur.
The offset voltage is displayed in the SYSTEM INFO window. It should be 2.5 V +/- 1.0
V for normal operation. If it goes close to 0 V or to 5 V the ECG will be flat lined by the
software and a Lead Off error message will exist. An easy check to see if a large offset
is due to the probe is to disconnect the probe from the ERT Module (no need to remove
it from the animal). If disconnecting the probe removes the offset, the probe is at fault.
In an emergency a faulty probe will work if placed in a plastic or rubber sleeve (e.g. a
thermometer cover or finger from a rubber glove).
The sleeve provides electrical
isolation.
Positioning the thermister temperature probe
The thermister temperature probe will distort the magnetic field for a few mm around the
tip creating a small signal void in the MR image. This artifact is normally only a problem
when imaging near the rectum. In that case the probe can be used as a skin probe
near the animal's head.
Under some conditions it is possible for the thermister temperature probe to heat from
interaction with the MR scanner's RF coil. Observation of the measured temperature
will indicate if this happens. If a temperature rise is observed when the scanner begins
to acquire data and the temperature decreases when the acquisition is complete,
reposition the ECG/T Module, Battery Pack and cable. A position near the center line of
the magnet bore is generally better than near the edge of the bore.
Charging the ERT Battery Pack
The ERT Battery Pack should be connected to the ERT battery charger when the
system is not in use. The battery pack voltage is between 5.8 V and 6.5 V. A fully
charged pack will operate for more than 15 hours when the battery is new. The battery
pack voltage is displayed in the "System Info" window (refer to Chapter 3).
The ERT battery pack charger is internal to the ERT Control/Gating Module.
An
optional wall charger is also available. The battery pack will obtain a full charge in less
than 2 hours. It is not necessary to deep discharge the battery or disconnect it from the
charger after it is fully charged.
Revision C, August 2013
4-7
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