Samsung ACCUVIX XG Instrukcja Użytkownika Pobierz pdf (Strona 45)

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Chapter 1 Safety

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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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

bioeffects varies with peak pressure and ultrasound frequency. The MI accounts for these two

factors. The higher the MI value, the greater the likelihood of mechanical bioeffects occurring but

there is no specific MI value that means that a mechanical effect will actually occur. The MI should

be used as a guide for implementing the ALARA principle.

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Thermal Index (TI) Display

The TI informs the user about the potential for temperature increase occuring at the body surface,

within body tissue, or at the point of focus of the ultrasound beam on bone. The TI is an estimate

of the temperature increase in specific body tissues. The actual amount of any temperature rise is

influenced by factors such as tissue type, vascularity, and mode of operation etc. The TI should be

used as a guide for implementing the ALARA principle.

The bone thermal index (TIb) informs the user about potential heating at or near the focus after

the ultrasound beam has passed through soft tissue or fluid, for example, at or near second or third

trimester fetal bone.

The cranial bone thermal index (TIc) informs the user about the potential heating of bone at or near

the surface, for example, cranial bone.

The soft tissue thermal index (TIs) informs the user about the potential for heating within soft

homogeneous tissue.

TIc is displayed when you select a trans-cranial application.

You can select TI Display in Utility > Setup > Display > Display.

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Mechanical and Thermal indices Display Precision and Accuracy

The Mechanical and Thermal Indices on the system are precise to 0.1 units.

The MI and TI display accuracy estimates for the system are given in the Acoustic Output Tables

manual. These accuracy estimates are based on the variability range of probes and systems, inherent

acoustic output modeling errors and measurement variability, as described below.

The displayed values should be interpreted as relative information to help the system operator

achieve the ALARA principle through prudent use of the system. The values should not be interpreted

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Samsung ACCUVIX XG Instrukcja Użytkownika Strona 45