The Dependence of Glomerular Capillary Hemorrhage Induced by Contrast Enhanced Diagnostic Ultrasound on Microbubble...

Area of Science:

• Biomedical Engineering
• Ultrasound Physics
• Nephrology

Background:

• Microbubbles (MBs) are used as contrast agents in diagnostic ultrasound.
• Understanding MB bioeffects, such as cavitational bioeffects, is crucial for safe ultrasound applications.
• A two-criterion model for MB-associated bioeffects has been proposed.

Purpose of the Study:

• To test a recently proposed two-criterion model for cavitational bioeffects in tissue using microbubbles (MBs).
• To investigate the relationship between microbubble size, ultrasound frequency, and glomerular capillary hemorrhage in rat kidneys.

Main Methods:

• Glomerular capillary hemorrhage was induced in rat kidneys using microbubble suspensions (1.6, 3.1, and 5.5 µm).
• Diagnostic ultrasound was applied at 3.6 MHz and 5.5 MHz with varying power settings.
• Petechial hemorrhage was quantified on kidney surfaces, and glomeruli were assessed via histology.

Main Results:

• Hemorrhage thresholds were similar for large and medium MBs but higher for small MBs.
• At 5.5 MHz, medium MBs showed a higher hemorrhage threshold than large MBs in histology.
• Observed pressure amplitude thresholds aligned with theoretical predictions.
• Optimal MB size counterintuitively increased with ultrasound frequency, as predicted by the model.

Conclusions:

• The findings support the two-criterion model for microbubble-associated capillary hemorrhage.
• Microbubble size and ultrasound frequency are critical factors influencing cavitational bioeffects.
• The study provides valuable insights into the mechanisms of ultrasound-induced tissue bioeffects.