PFOB sonosensitive microdroplets: determining their interaction radii with focused ultrasound using MR thermometry...

Area of Science:

• Biophysics
• Medical Imaging
• Acoustic Therapy

Background:

• Perfluorocarbon droplets enhance focused ultrasound (FUS) therapies.
• They reduce required power and prefocal heating, increasing thermal dose in vascularized tissues.
• Heat enhancement saturates at higher droplet concentrations.

Purpose of the Study:

• To empirically model the saturating heating effects of perfluorocarbon droplets during FUS.
• To determine the interaction radius and volume of these droplets with FUS.
• To understand the dose-response relationship and physical heating mechanisms.

Main Methods:

• Magnetic resonance thermometry and FUS were used with varying droplet concentrations.
• Droplets with a mean diameter of 1.9–2.3 µm circulated through a perfused phantom.
• Simulations estimated the empirical interaction radius.

Main Results:

• The interaction radius was experimentally determined from ultrasonic absorption coefficients.
• Simulations indicated the interaction radius is ~12.5 times the droplet's geometrical radius.
• This results in an interaction volume ~2000 times larger than the geometrical volume.

Conclusions:

• Results provide dose-response information for perfluorocarbon droplets in FUS.
• Interaction radii were measured with 15% precision.
• Insights into the physical heating mechanism of droplets with FUS were gained.