Fast dynamic electron paramagnetic resonance (EPR) oxygen imaging using low-rank tensors

Area of Science:

• Biomedical Imaging
• Medical Physics
• Cancer Research

Background:

• Tumor hypoxia significantly contributes to radiotherapy resistance.
• Both chronic and transient hypoxia are implicated in treatment failure.
• Conventional Electron Paramagnetic Resonance Imaging (EPRI) offers high resolution but lacks the speed to capture rapid oxygen fluctuations.

Purpose of the Study:

• To develop an accelerated 3D dynamic EPRI method for imaging transient hypoxia.
• To enable real-time monitoring of oxygen changes in vivo.
• To investigate the role of transient hypoxia in tumor radioresistance.

Main Methods:

• A novel low-rank tensor model was employed to decouple imaging speed, spatial resolution, and accuracy.
• A specialized sparse sampling strategy and image reconstruction algorithm were developed.
• The method was validated using simulations and in vivo experiments in tumor-bearing mice.

Main Results:

• The new method achieves 3D dynamic EPRI at 2 frames per minute, significantly faster than conventional techniques.
• This accelerated imaging speed is sufficient to capture transient hypoxia dynamics.
• Simulations and in vivo data confirmed the method's quality and utility for dynamic pO2 mapping.

Conclusions:

• The developed accelerated EPRI technique allows for rapid 3D oxygen imaging in vivo.
• This advancement facilitates the study of transient hypoxia, a critical factor in tumor radioresistance.
• The method holds promise for improving our understanding and treatment of hypoxic tumors.