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HD11 XE Getting Started
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Safety
time. Diagnostic ultrasound is an important tool in medicine, and, like any tool, it
should be used efficiently and effectively.
Output Display
The system output display comprises two basic indices: a mechanical index and a
thermal index. The thermal index further consists of the following indices: soft
tissue (TIS), bone (TIB), and cranial bone (TIC). One of these three thermal indi-
ces will be displayed at all times. Which one depends upon the system preset or
user choice, depending upon the application at hand.
The mechanical index (MI) is continuously displayed over the range of 0.0 to max-
imum output (see the HD11 XE Acoustic Output Tables), in increments of 0.1 for all
applications except contrast, where the minimum increment is 0.01.
The thermal index consists of the three indices, and only one of these is displayed
at any one time. Each transducer application has a default selection that is appro-
priate for that combination. The TIB, TIS, or TIC is continuously displayed over
the range of 0.0 to maximum output, based on the transducer and application, in
increments of 0.1.
The decision as to which of the three thermal indices to display should be based
on the following criteria:
• Appropriate index for the application: TIS is used for imaging soft tissue, TIB
for a focus at or near bone, and TIC for imaging through bone near the sur-
face, as in a cranial exam.
•Mitigating factors that might create artificially high or low thermal index read-
ings: location of fluid or bone, or blood flow. For example, is there a highly
attenuating tissue path so that the actual potential for local zone heating is less
than the thermal index displays.
• Scanned modes versus unscanned modes of operation affect the thermal
index. For scanned modes, heating tends to be near the surface; for
unscanned modes, the potential for heating tends to be deeper in the focal
zone.
• Always limit ultrasound exposure time. Do not rush the exam. Ensure that
the indices are kept to a minimum and that exposure time is limited without
compromising diagnostic sensitivity.
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