Recently, a simple solution was found to the image distom
tion problem caused in the oximeter by high-frequency elec
trical noise from the pulsing of the gradient and radio-fme
quency coils. The cable connecting the sensor to the oximeter
(Nonin 8604D-L; Nonin Medical, Plymouth, Minn) was
wound around two radio-frequency chokes (low-pass filters).
These chokes prevent high-frequency noise from reaching the
MRimager by means of the oximetemcable. No imaging arti
facts existed when we used this arrangement with a 1.5-T sys
tem (Signa; GE Medica' Systems, Milwaukee). In addition, the
oximeter functioned continuously, even during pulsing.
One other problem of lesser importance is that oximeters
have metal cases and components that could be pulled into
the magnet; typically, this problem can be solved by placing
the oximetem sufficiently far from the magnet. Similarly, the
radio-frequency chokes are ferromagnetic and must be placed
sufficiently far from the magnet or secured.
As anesthesiologists, we believe that sedated patients me
quire appropriate monitoring, including both careful observa
tion by skilled clinicians and measurement of clinical parame
ters including heart and respiratory mates, airway patency,
ventilation, and oxygenation. Technologies other than oxi
metry have been readily available to monitor these other pa
rameters. Now that an oximetem can safely and continuously
monitor patients undergoing MR imaging without creating
imaging artifacts, we believe that oximetry should be consid
ered part of the standard practice for monitoring sedated pe
diatric patients during radiologic procedures.