Quantitative evaluation of pulmonary gas-exchange function using hyperpolarized ¹²⁹ Xe CEST MRS and MRI

Area of Science:

• Medical Imaging
• Pulmonary Medicine
• Magnetic Resonance Imaging

Background:

• Hyperpolarized 129Xe gas MRI is valuable for lung structure and function assessment.
• Existing methods like CSSR and XTC provide quantitative lung information.
• Hyperpolarized 129Xe chemical exchange saturation transfer (Hyper-CEST) is used for biosensors but its in vivo lung application is unclear.

Purpose of the Study:

• To assess the feasibility of using Hyper-CEST for in vivo pulmonary gas exchange quantification.
• To globally and regionally evaluate lung gas exchange using Hyper-CEST.
• To define and validate a new parameter for gas exchange in lung diseases.

Main Methods:

• Utilized Hyper-CEST with hyperpolarized 129Xe MRI and MRS.
• Defined a new parameter, pulmonary apparent gas exchange time constant (Tapp).
• Applied the technique to a rat model of chronic obstructive pulmonary disease (COPD).

Main Results:

• The pulmonary apparent gas exchange time constant (Tapp) significantly increased in COPD rats (0.63s to 0.95s).
• Spatial distribution maps of Tapp revealed regional increases in COPD rat lungs.
• Hyperpolarized 129Xe CEST MR demonstrated effectiveness in quantifying pulmonary gas exchange.

Conclusions:

• Hyperpolarized 129Xe CEST MR is an effective method for global and regional pulmonary gas exchange quantification.
• The defined Tapp parameter shows potential for diagnosing lung diseases affecting gas exchange.
• This technique could aid in the diagnosis of conditions like COPD.