Samsung SONOACE R5 Manual do Utilizador descarregar pdf (Página 40)

1-24

User Manual

Some factors might create articially high or low thermal index readings e.g. presence of uid or bone,

or the ow 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 aect 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.

■

Mechanical Index (MI) Display

Mechanical bioeects 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

bioeects 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 bioeects occurring but

there is no specic MI value that means that a mechanical eect will actually occur. The MI should

be used as a guide for implementing the ALARA principle.

■

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 specic body tissues. The actual amount of any temperature rise is

inuenced 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 uid, 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.

You can select either TIs or TIb using the TIs/TIb selection on the Miscellaneous system setups. TIc is

displayed when you select a trans-cranial application.

1 2 ... 35 36 37 38 39 40 41 42 43 44 45 ... 453 454

Sem comentários

Samsung SONOACE R5 Manual do Utilizador Página 40