GE Vscan Air, Руководство пользователя

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Acoustic Output
Vscan Air
–
User Manual
8-3
Direction GP092020-1EN Rev 18
Acoustic Output
The real-time display of acoustic output indices
The Vscan Air software have real-time display features
according to IEC62359 Ed.2. A thermal (TI) and a mechanical
(MI) index is displayed. These two indices are intended to
estimate the potential for thermal and mechanical bioeffects
induced by ultrasound. Both TI and MI are displayed with
increments of 0.1. The displayed (estimated) TI and MI are
nominal values.
Thermal Index
TI is defined as:
where: W
0
is the time-averaged acoustic power and W
deg
is the
estimated power necessary to raise the target tissue 1°C.
The displayed TI is an estimate of temperature increase of soft
tissue or bone, presented to make it easier for the operator to
implement the ALARA (As Low As Reasonably Achievable)
principle. There are three thermal index categories:
• TIS: Soft tissue thermal index. The main TI category. Used
for applications that do not image bone.
• TIB: Bone thermal index (bone located in a focal region).
Used for fetal application.
• TIC: Cranial bone thermal index (bone located close to the
surface). Used for transcranial application.
The correct category is chosen based on display standard,
mode of operation and chosen application, and the relevant TI
category presented to the operator. It is therefore important that
the operator chooses the right application.
Vscan Air will for each scan setup calculate and limit TI for the
chosen index category to 3.0.