In vivo multisite oximetry using EPR-NMR coimaging

Area of Science:

• Biomedical Engineering
• Medical Imaging
• Biophysics

Background:

• In vivo oximetry is crucial for understanding physiological processes and disease states.
• Existing methods for measuring tissue oxygen partial pressure (pO₂) have limitations in speed and spatial coverage.
• Electron paramagnetic resonance (EPR) imaging offers potential for non-invasive oximetry, but requires precise anatomical localization.

Purpose of the Study:

• To develop and validate a rapid, simultaneous multi-organ in vivo oximetry technique using coimaging.
• To integrate EPR imaging with MRI for precise anatomical referencing of oxygen measurements.
• To improve the efficiency of EPR data acquisition for enhanced clinical relevance.

Main Methods:

• A hybrid EPR-NMR coimaging instrument was utilized for simultaneous measurements.
• Oxygen-sensitive particulate EPR probes were implanted at localized sites across multiple organs in a live mouse.
• Three-dimensional MRI provided anatomical visualization to precisely locate implant sites.
• A generalized EPR data model was proposed to address radiofrequency (RF) phase inhomogeneities.

Main Results:

• Simultaneous pO₂ measurements were successfully obtained across multiple organs in vivo.
• MRI accurately guided the localization of EPR probe implant sites.
• The proposed EPR data model and optimized acquisition strategy reduced data collection requirements by over an order of magnitude.
• The technique demonstrated feasibility for clinically relevant models.

Conclusions:

• Coimaging of EPR and MRI enables rapid and spatially resolved in vivo oximetry.
• This integrated approach enhances the precision and efficiency of oxygen measurements in biological tissues.
• The developed method holds significant promise for advancing preclinical research and potential clinical applications in oxygen-related pathologies.