Cavitation Threshold in the Porcine Crystalline Lens

Area of Science:

• Biomedical Engineering
• Ophthalmology
• Acoustics

Background:

• Cataract formation is a significant cause of vision impairment.
• Understanding ultrasonic cavitation is crucial for developing novel therapeutic interventions.
• Porcine crystalline lenses serve as a relevant model for human ocular tissues.

Purpose of the Study:

• To determine ultrasonic cavitation thresholds in porcine crystalline lenses of varying ages.
• To assess the impact of different duty cycles (DCs) on cavitation and tissue integrity.
• To explore the feasibility of using ultra-low DCs for safe and effective ultrasound applications.

Main Methods:

• Utilized a 2 MHz transducer to expose porcine lenses (young and old) to varying peak negative pressures.
• Recorded and analyzed cavitation signals to estimate threshold pressures.
• Investigated duty cycles ranging from 0.025% to 0.000006%, including an ultra-low duty cycle (0.6e-5%).

Main Results:

• Cavitation thresholds were determined, with an ultra-low DC (0.6e-5%) yielding a threshold of -36.1 MPa without observable macroscopic cataracts.
• Higher DCs (e.g., 0.1%) led to cavitation thresholds around -31.7 MPa but caused severe cataracts.
• Significant variations in cavitation thresholds were noted between samples and age groups, attributed to differences in viscoelastic properties and water content.

Conclusions:

• Increasing negative pressure trends towards higher cavitation probability.
• Ultra-low duty cycles demonstrate feasibility for cavitation nucleation while minimizing heat deposition, suggesting potential for therapeutic use.
• Further research is needed to explore the safety aspects of this technique.