Samsung MySono U5 Manual do Utilizador descarregar pdf (Página 36)

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Operation Manual

Applying ALARA

The system-imaging mode used depends upon the information needed. 2D mode and M mode

imaging provide anatomical information, whilst Doppler, Power and Color imaging provide

information about blood ow. Scanning modes, such as 2D mode, Power and Color, spread the

ultrasound energy all over the imaging area, while non-scanning modes, such as M mode and Doppler,

focus the ultrasound energy at one point. Understanding the nature of the imaging mode being used

allows the sonographer to apply the ALARA principle with informed judgment. The probe frequency,

system set-up values, scanning techniques, and operator experience aid the sonographer in meeting

the denition of the ALARA principle. The decision regarding the volume of acoustic output is, in the

nal analysis, up to the system operator. This decision must be based on the following factors: type of

patient, type of exam, patient history, ease or diculty of obtaining diagnostically useful information,

and the potential localized heating of the patient due to probe surface temperatures. Prudent use

of the system involves patient exposure being limited to the lowest index reading for the shortest

amount of time necessary to achieve acceptable diagnostic results.

Although a high index reading does not mean that a bioeect is actually occurring, a high index

reading should nevertheless be taken seriously. Every eort should be made to reduce the possible

eects of a high index reading. Limiting exposure time is an eective way to accomplish this goal.

There are several system controls that the operator can use to adjust the image quality and limit the

acoustic intensity. These controls relate to the techniques that an operator might use to implement

ALARA. These controls can be divided into three categories: direct, indirect, and receiver control.

Direct Controls

Application selection and output intensity control directly aect acoustic intensity. There are dierent

ranges of allowable intensity or output based on user selection. Selecting the correct range of acoustic

intensity for the application is one of the rst things required during any exam. For example, peripheral

vascular intensity levels are not recommended for fetal exams. Some systems automatically select the

proper range for a particular procedure, whilst others require manual selection. Ultimately, the user

bears the responsibility for proper clinical use. The Samsung Medison system provides both automatic

and user-denable settings.

Output has a direct impact on acoustic intensity. Once the application has been established, the

output control can be used to increase or decrease the intensity output. The output control allows

you to select intensity levels less than the dened maximum. Prudent use dictates that you select the

lowest output intensity consistent with good image quality.

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Samsung MySono U5 Manual do Utilizador Página 36