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Ultrasonic contrast agents: safety considerations reviewed.
1Joint Physics Department, Institute of Cancer Research, Royal Marsden Hospital, Sutton, Surrey SM2 5PT, UK. gail@icr.ac.uk
European Journal of Radiology
|February 28, 2002
Summary
Ultrasonic contrast agents, used in medical imaging, can cause red blood cell damage and internal bleeding in animals. Safety thresholds for these microbubbles are near clinical limits, though no human adverse effects are reported.
Area of Science:
- Biomedical Engineering
- Acoustics
- Medical Imaging
Background:
- Ultrasonic contrast agents are gas-filled microbubbles used to enhance ultrasound imaging.
- Their primary applications are in cardiology and oncology.
- Microbubbles can also induce acoustic cavitation, raising safety concerns.
Purpose of the Study:
- To investigate the acoustic safety of ultrasonic contrast agents.
- To determine the thresholds for microbubble-induced bioeffects.
Main Methods:
- In vitro studies with red blood cell suspensions exposed to ultrasound.
- In vivo studies in experimental animals with infused contrast agents.
- Evaluation of Mechanical Index (MI) thresholds for observed effects.
Main Results:
- In vitro: Ultrasound exposure caused red blood cell hemolysis (rupture).
- In vivo: Contrast agents enhanced petechiae and intestinal hemorrhage in animals.
- Acoustic thresholds for in vitro effects are within clinical scanner ranges.
- In vivo thresholds approach the upper limits of clinical exposure levels.
Conclusions:
- Ultrasonic contrast agents possess the potential for bioeffects, including hemolysis and hemorrhage.
- Acoustic safety margins for in vivo applications are narrow.
- Further research is needed to fully understand and mitigate risks in clinical use.