A simplified empirical model to estimate oxygen relaxivity at different magnetic fields

Area of Science:

• Biomedical Engineering
• Magnetic Resonance Imaging
• Biophysics

Background:

• Oxygen's effect on longitudinal relaxation rate (R1) is crucial for MRI-based oxygenation measurements.
• The relationship between oxygen partial pressure (pO2) and R1 is linear, with relaxivity (r1Ox) as the slope.
• Reported r1Ox values show significant variability influenced by field strength and temperature.

Purpose of the Study:

• To compile reported empirical values of oxygen relaxivity (r1Ox) for researchers.
• To develop an empirical model for estimating r1Ox in water, saline, plasma, and vitreous fluids.
• To account for the influence of magnetic field strength and temperature on r1Ox.

Main Methods:

• Literature review and compilation of 28 reported empirical r1Ox values.
• Development of an empirical model correlating r1Ox with field strength and temperature.
• Validation of the model against compiled literature data.

Main Results:

• A comprehensive dataset of 28 empirical r1Ox values was assembled.
• An empirical model was established to predict r1Ox in various fluids.
• The model demonstrated strong agreement (R² = 0.93) with literature data across a wide range of field strengths (0.011–8.45 T) and temperatures (21–40 °C).

Conclusions:

• The compiled data and developed model serve as a valuable resource for researchers.
• The model enables accurate estimation of pO2 in simple and bodily fluids using MRI.
• This facilitates quantitative oxygenation measurements in phantoms and in vivo applications.