The results obtained in this study are similar to those observed by Backley et al in 2011(3), where less than 70% of ultrasound operators forming part of the Radiology departments where aware of the bioeffects and ODS indices.
We the authors agree with the review by Nyborg in 2001(9), and consider essential that all ultrasound operators know the bioeffects associated and the risks derived from each imaging mode. This knowledge should result in adequate decision-making when considering the risks vs benefits, especially since the implementation of TRACK 3 where there is a tendency for the operator to regulate output(8).
We consider it necessary to implement training programs for the operator to better assess risk/benefit of each examination. Operators should understand the mechanisms behind the bioeffects of ultrasound and be aware of the risks involved with each imaging mode. They should be able to act accordingly in order to adjust the acoustic output power in addition to other parameters that may be contributing to increasing risk indices(6,8). It is also important to consider time spent performing each ultrasound examination as this is usually related to the operator´s ability and examination difficulty(10).
In our survey, we have shown that indices of biological risk present in ultrasound equipment are not well known, and so not frequently considered. Less than 40% of users are aware of them and less than 22% take them into consideration.
Due to uncertainties in the measurement of acoustic output and in situ estimation, the thermal and mechanical indices are only an approximation to the risk of producing bioeffects from ultrasound. These do not indicate the real values of acoustic output or related biophysical parameters(8). In addition, the TI does not pinpoint the exact area of increased thermal activity(7), and as it is not an exact measure of the increase in temperature(6), operator awareness of the ODS is in itself insufficient for monitoring patient safety(3).
These observations could lead us to question whether the ODS are currently a useful alert system for ultrasound operators.
When questioned on at the ALARA criteria, we observed that only 109 of the 488 respondents (22.3%) took the indicators into consideration, either by reducing the acoustic power (16.2%; n=79) or other actions. These data are lower than those obtained by Martin et al (10) which found that 60% of participants in the United Kingdom (n=276) considered the ALARA criteria.
In absolute terms, and in response to the second objective of this study, we can observe that 77.7% of all respondents (n=488) do not take into account the current indicators which warn of the potential risks associated with ultrasound on live tissues, either through unfamiliarity of the ODS or inaction.
Conclusions
- A high number of ultrasound operators are unaware of ultrasound bioeffects.
- The current indices, the “mechanical index” and the “thermal index” may not be sufficient to control for the bioeffects of ultrasound.
- Education policies should be put in place that guarantees that operators are aware of the hazards of ultrasound and how to reduce their effects.
- In addition to the current ODS, it may be beneficial to implement the acoustic power outputs on the display as W/cm2.
