Samsung HS70A - Output Display Features

Chapter 1 Safety 1 - 27
up, which ultimately increases the time. Diagnostic ultrasound is an important tool in medicine, and,
like any tool, should be used efficiently and effectively.
▐Output Display Features
The system output display comprises two basic indices: a mechanical index and a thermal index. The
thermal index consists of the following indices: soft tissue (TIs), bone (TIb) and cranial bone (TIc). One
of these three thermal indices will be displayed at all times. Which one depends upon the system’s
default setting or user choice, depending upon the application at hand.
The mechanical index is continuously displayed over the range of 0.0 to 1.9, in increments of 0.1. The
thermal index consists of the three indices, and only one of these is displayed at any one time. Each
probe application has a default selection that is appropriate for that combination. The TIb or TIs is
continuously displayed over the range of 0.0 to the maximum output, based on the probe and
application, in increments of 0.1.
The application-specific nature of the default setting is also an important factor of index behavior. The
default setting is a system control state, which is preset by the manufacturer or the operator. The
system has default index settings for the probe application. The default settings are invoked
automatically by the Ultrasound System when power is turned on, new patient data is entered into the
system database, or a change in application takes place. 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; and TIb for a focus at or near
bone.Some factors might create artificially high or low thermal index readings, e.g. the presence of
fluid or bone, or the flow of blood. A highly attenuating tissue path, for example, will cause the
potential for local zone heating to be 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 but do not rush the exam. Ensure that the indices are kept to a
minimum and that exposure time is limited without compromising diagnostic sensitivity.
 Mechanical Index (MI) Display
Mechanical bioeffects are threshold phenomena that occur when a certain level of output is
exceeded. The threshold level varies, however, with the type of tissue. The potential for
mechanical biological effects varies with peak pressure and ultrasound frequency. The MI