Nonlinear model for capillary-tissue oxygen transport and metabolism

Area of Science:

• Physiology
• Biophysics
• Medical Imaging

Background:

• Direct measurement of oxygen consumption in small tissue regions is challenging.
• Positron emission tomography (PET) with tracer 15O-oxygen allows regional assessment of oxygen transport and metabolism.
• Mathematical modeling of tracer kinetics is crucial for interpreting regional concentration-time curves.

Purpose of the Study:

• To develop an axially-distributed capillary-tissue model for quantifying regional oxygen consumption using PET.
• To account for complex physiological processes including oxygen convection, binding, transport, and metabolism.
• To optimize computational speed for routine experimental data analysis.

Main Methods:

• Developed an axially-distributed capillary-tissue model incorporating oxygen convection, nonlinear binding, transmembrane transport, axial dispersion, and water formation.
• Utilized a parent model for nontracer oxygen to govern solutions for tracer oxygen and water models.
• Fitted model solutions to experimental tracer curves (regional tissue content or venous outflow) to estimate parameters.

Main Results:

• The model accurately estimates oxygen consumption, extraction, and venous partial pressure of oxygen (pO2).
• Estimated myocardial oxygen consumption showed good agreement with direct Fick method measurements.
• The model demonstrated relative insensitivity to data noise.

Conclusions:

• The developed mathematical model provides a robust method for estimating regional oxygen consumption using PET.
• The model's features allow for wide applicability to various organs and external detection methods.
• This approach enhances the understanding of tissue oxygen metabolism and transport.