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Microbubbles induce renal hemorrhage when exposed to diagnostic ultrasound in anesthetized rats
James H Wible1, Karen P Galen, Jolette K Wojdyla
1Mallinckrodt Imaging, St. Louis, MO, USA. james.wible@tycohealthcare.com
Abstract:
The generation of ultrasound (US) bioeffects using a clinical imaging system is controversial. We tested the hypothesis that the presence of microbubbles in the US field of a medical imager induces biologic effects. Both kidneys of anesthetized rats were insonified for 5 min using a medical imaging system after the administration of microbubbles. One kidney was insonified using a continuous mode (30 Hz) and the opposite kidney was insonified using an intermittent (1 Hz) technique. The microbubbles were exposed to three different transducer frequencies and four transducer output powers. After insonification, the animals were euthanized, the kidneys were removed and their gross appearance scored under "blinded" conditions using a defined scale. After the administration of microbubbles, US imaging of the kidney caused hemorrhage in the renal tissue. The severity and area of hemorrhage increased with an increase in the transducer power and a decrease in the transducer frequency. Intermittent insonification in the presence of microbubbles produced a greater degree of renal hemorrhage than continuous imaging techniques.
Insights
Ultrasound (US) imaging with microbubbles can cause kidney bleeding in rats. Higher power and lower frequencies increased hemorrhage severity, with intermittent US causing more damage than continuous modes.
Area of Science:
- Medical Imaging
- Ultrasound Bioeffects
- Nephrology
Background:
- The bioeffects of clinical ultrasound (US) imaging are debated.
- Microbubbles are commonly used as contrast agents in medical imaging.
Purpose of the Study:
- To investigate if microbubbles in the ultrasound field of a medical imager induce biologic effects.
- To determine the relationship between ultrasound parameters and induced bioeffects.
Main Methods:
- Rat kidneys were insonified using a clinical imaging system after microbubble administration.
- Insonification was performed in continuous (30 Hz) and intermittent (1 Hz) modes.
- Exposure involved varying transducer frequencies and output powers.
Main Results:
- Ultrasound imaging in the presence of microbubbles caused renal hemorrhage.
- Hemorrhage severity and area increased with higher transducer power and lower frequencies.
- Intermittent insonification resulted in greater renal hemorrhage than continuous imaging.
Conclusions:
- Microbubbles can potentiate ultrasound-induced bioeffects, specifically hemorrhage, in renal tissue.
- Ultrasound power and frequency are critical factors influencing the extent of bioeffects.
- Imaging modes (continuous vs. intermittent) impact the severity of microbubble-mediated US bioeffects.