A loop resonator for slice-selective in vivo EPR imaging in rats

Area of Science:

• Biomedical Engineering
• Magnetic Resonance Imaging
• Spectroscopy

Background:

• Electron paramagnetic resonance (EPR) is a valuable technique for studying paramagnetic species.
• Developing specialized resonators is crucial for in vivo EPR applications, especially in small animal models.

Purpose of the Study:

• To develop and evaluate a loop resonator for 300 MHz continuous-wave EPR (CW-EPR) spectroscopy and imaging in live rats.
• To assess the performance of the resonator in terms of radiofrequency magnetic field generation and quality factor.

Main Methods:

• A single-turn loop resonator (55 mm diameter) was designed for a 300 MHz CW-EPR system.
• The resonator's efficiency and quality factor were measured with and without a live rat.
• EPR imaging was performed using a nitroxide spin probe (3-CP) infused intravenously into the rat.

Main Results:

• The resonator achieved an efficiency of 38 microT/W(1/2) at its center.
• An unloaded quality factor of 430 was obtained, decreasing to 18 when a 350 g rat was introduced.
• Successful EPR imaging of 3-CP distribution in the lower abdomen of a live rat was demonstrated.

Conclusions:

• The developed loop resonator is suitable for in vivo CW-EPR spectroscopy and imaging in live rats.
• The system enables visualization of probe distribution within a live animal model, opening possibilities for physiological studies.