Towards Photoswitchable Contrast Agents for Absolute 3D Temperature MR Imaging

Area of Science:

• Biomedical Imaging
• Chemical Physics
• Materials Science

Background:

• Temperature serves as a critical clinical marker for tissue metabolism, inflammation, and tumor detection.
• Noninvasive temperature monitoring using Magnetic Resonance Imaging (MRI) is increasingly vital for physiological parameter assessment.

Purpose of the Study:

• To present a proof-of-principle for MRI contrast agents enabling absolute and concentration-independent temperature imaging.
• To develop novel contrast agents for precise temperature determination in biological tissues.

Main Methods:

• Utilized azoimidazole substituted Ni^II porphyrins undergoing Light-Driven Coordination-Induced Spin State Switching (LD-CISSS).
• Monitored the cis-to-trans isomerization kinetics using standard clinical MRI sequences.
• Translated determined half-lives directly into absolute temperature values.

Main Results:

• Developed temperature-responsive contrast agents tested in methanol-based gels.
• Generated high-resolution temperature maps (0.13×0.13×1.1 mm) with minimal temperature errors (<0.22 °C).
• Demonstrated the method's speed for capturing dynamic temperature changes, like heat flow.

Conclusions:

• The developed contrast agents offer a novel approach for absolute temperature imaging using MRI.
• This technique provides concentration-independent temperature measurements, crucial for clinical applications.
• The high spatial resolution and accuracy support potential use in diagnosing and monitoring conditions like inflammation and tumors.