Konica Minolta SONIMAGE HS2 - MI;TI Limits and ALARA Principle

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9.1 Basic Knowledge of MI/TI
Chapter 9
The idea of MI/TI has been introduced recently to increase the diagnostic capability, promoting relaxation of these
acoustic power limits (Track 3).
Maximum limit for MI/TI display (Track 3)
Application I
spta.3
(mW/cm
2
)
I
sppa.3
≤
190 (W/cm
2
) or MI
≤
1.9
All regions (except eyes) 720
With this trend, management of the level of acoustic power has been transferred from manufacturers to users.
IMPORTANT
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• Note the following in regard to output setting of the acoustic power level.
The FDA allows ultrasound equipment to output acoustic power level Track 3, which is higher than Track 1, provided
that MI/TI values are displayed on the system. This means that users have a higher degree of responsibility for safety
than manufacturers.
Against this background, users are required to understand the ultrasound bioe󰀨ects and their cause. They are also
required to understand that the introduction of MI/TI will increase the diagnostic capability.
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(5) ALARA (As Low As Reasonably Achievable)
ALARA refers to a practice to control the ultrasound energy at the lowest possible level that would not a󰀨ect di-
agnosis. It is required to practice ALARA when using ultrasound energy. Practicing ALARA ensures that the total
energy level is controlled at the lowest possible level that would not a󰀨ect bodies that are currently being diag-
nosed. The ultrasound energy is controlled by output intensity and total radiation time.
The output intensity necessary for examinations di󰀨ers depending on the patient and the clinical case.
IMPORTANT
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• It is strictly required that acoustic output is set based on the ALARA (As Low As Reasonably Achievable) principle.
However, not all examinations can be performed with an extremely low level of acoustic energy. Controlling the
acoustic level at an extremely low level leads to low-quality images or insu󰀩cient Doppler signals, adversely a󰀨ecting
the reliability of the diagnosis.
However, increasing the acoustic power more than necessary does not always contribute to an increase in quality of
information required for diagnosis, rather increasing the risk of generating bioe󰀨ects.
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