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ble or air pocket (for example, in the lung or intestines). During the cavitation process, the sound wave may cause the
bubble to contract or vibrate. This vibration can cause the bubbles to explode and damage the tissue. The mechanical
index (MI) was created to help users evaluate the likelihood of cavitations and the related side effects.
The MI recognises the importance of non-thermal processes, and especially of cavitations. The index is an attempt to
indicate the probability of them occurring in the tissue.
2.6
Scanning patients and training
The IEC60601-2-37 output display standard allows users to be responsible for the safe use of this ultrasound system.
Therefore, for all of these diagnostic modalities, it is the responsibility of the user to understand the risks of the output of
the systems and to act appropriately in order to obtain the desired diagnostic information while minimising risk to the pa-
tient.
Follow these usage guidelines for safe operation:
In order to maintain proper cleanliness of the probes, always clean them between patients. Always use a disin-
fected sheath on all EV/ER probes and during every examination.
Continuously move the probe, rather than letting it rest in a single spot, so as to avoid elevated temperatures in any
one part of the patient’s body.
Keep the probe away from the patient when not actively scanning.
Make sure you are familiar with the meaning of the TI, TIS, TIB, TIC and MI output displays, as well as with the rela-
tionship between these parameters and with the thermal/bioeffect on the tissue.
Expose the patient to only the very lowest practical transmitting power levels for the shortest time possible to achieve a
satisfactory diagnosis (ALARA - As Low As Reasonably Achievable).
2.6.1
Guidelines for safe scanning
Ultrasound should only be used for medical diagnosis and should only be operated by trained medical personnel.
Diagnostic ultrasound procedures should be performed only by personnel who are fully familiar with and trained in the
use of the equipment, who can safely interpret the results and images, and are sure in the use of ultrasound (including
training on potential hazards).
Operators must be aware of the possible influences of device operation and the operating mode (e.g. B mode) and
know the probe frequencies for thermal and cavitation hazards.
Select a low setting for each new patient. Output should only be increased during the examination if penetration is
required to achieve a satisfactory result, and only after the gain control has been moved to its maximum value.
Maintain the shortest examination time necessary to produce a useful diagnostic result.
Do not hold the probe at a fixed point for any longer than is necessary. The still-frame and cine loop function options
allow images to be reviewed and discussed with the patient without exposing the patient to continuous scanning.
Do not use an endocavitary probe if the probe noticeably heats up by itself when operated in the air. Although this
applies to all probes, take particular care during transvaginal exams during the first eight weeks of pregnancy.
Take particular care to reduce output and minimise the exposure time of an embryo or fetus when the temperature of the
mother is already elevated.
Take particular care to minimise the risk of thermal hazard during the ultrasound examination if: an embryo is less than
eight weeks old, or when examining the head, brain or spine of any fetus or neonate.
The user must always monitor the temperature index (TI) and mechanical index (MI) on the screen and select the
settings in such a way as to keep them as low as possible while still providing diagnostically useful results. For obstet-
ric examinations, the TIS (thermal index for soft tissue) should be monitored during the scans in the first eight weeks
of pregnancy, and after that, the TIB (thermal index in bone). In applications where the probe is very close to bone