Modeling the detectability of vesicoureteral reflux using microwave radiometry

Area of Science:

• Biomedical Engineering
• Medical Imaging
• Radiometry

Background:

• Vesicoureteral reflux (VUR) is a condition where urine flows backward into the kidneys.
• Current detection methods for VUR can be invasive.
• Noninvasive methods for VUR detection are highly desirable.

Purpose of the Study:

• To model and design a microwave radiometry system for noninvasive VUR detection.
• To determine optimal antenna parameters and receiver sensitivity for detecting warm urine reflux.
• To evaluate the system's feasibility using realistic anatomical models and thermal simulations.

Main Methods:

• Utilized computed tomography (CT) data to create 3D tissue models of pediatric kidneys.
• Designed and simulated a microstrip log spiral antenna with a dielectric matching layer and metal shielding.
• Performed transient thermal simulations to calculate minimum detectable temperature changes for refluxing urine.

Main Results:

• Optimized antenna parameters (center frequency 1.35 GHz, band 500 MHz) and aperture radius (30-40 mm) for deep target detection.
• Achieved a minimum detectable temperature change (deltaT(B)) of 0.1 K for 15 mL of 40°C urine at 35 mm depth.
• Simulations showed improved performance with antenna and matching layer enclosed in a metal cup.

Conclusions:

• A microwave radiometry system with specific parameters (1.35 GHz, 500 MHz bandwidth, <0.1 K sensitivity) is suitable for noninvasive VUR detection.
• The designed log spiral antenna and shielding enhance detection capabilities.
• Numerical studies support the feasibility of this noninvasive diagnostic approach.