10
HD11 XE Getting Started
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TEE Transducers
Leakage Current
For the TEE transducers discussed in this manual, the insertion tube and tip are
type BF , as described in IEC 60601-1. There are no exposed conductive sur-
faces distal to the control housing. Within the flexible shaft, all active circuits and
conductors are surrounded by a chassis-grounded shield that runs the length of
the transducer.
If the outer layer of the shaft is punctured or cracked, a patient’s esophagus could
be exposed to chassis leakage current. This leakage current is not hazardous pro-
vided that the ground connector (third wire) in the ultrasound system power
cable is intact and is connected to a properly grounded wall outlet. Even if the
ground connector breaks, leakage current does not exceed 100 µΑ when con-
nected to a 120-V outlet, or 200 µΑ when connected to a 240-V outlet.
Leakage hazards are further reduced when the ultrasound system is plugged into
an isolated power outlet, which is standard in most operating rooms.
Electrosurgical Units
Electrosurgical units (ESUs) and other devices intentionally introduce radio fre-
quency electromagnetic fields or currents into patients. Because imaging ultra-
sound frequencies are coincidentally in the radio frequency range, ultrasound
transducer circuits are susceptible to radio frequency interference. While an ESU
is in use, severe noise interferes with the black-and-white image and completely
obliterates the color image.
Combinations of failures in an ESU or other device and in the outer layer of the
transducer shaft can cause electrosurgical currents to return along the transducer
conductors. This could burn the patient, and the ultrasound system and the trans-
ducer could also be damaged. Be aware that a disposable transducer cover pro-
vides no protective electrical insulation at ESU frequencies.
Pacemakers
For information on the use of pacemakers and transducers, see “Pacemakers” on
page 51.
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