Using hyperpolarized ¹²⁹Xe gas-exchange MRI to model the regional airspace, membrane, and capillary contributions to...

Area of Science:

• Pulmonary Medicine
• Medical Imaging
• Physiology

Background:

• Hyperpolarized 129Xe MRI offers 3D mapping of pulmonary ventilation, interstitial barrier uptake, and red blood cell (RBC) transfer.
• The precise physiological interpretation of these 129Xe MRI parameters for assessing lung function remains to be fully established.
• Diffusing capacity for carbon monoxide (DLCO) is a critical measure of pulmonary gas exchange.

Purpose of the Study:

• To develop and validate a model using hyperpolarized 129Xe MRI to estimate the components of DLCO: accessible alveolar volume (VA), membrane conductance, and capillary blood volume.
• To correlate image-derived DLCO with conventionally measured DLCO in a cohort of healthy subjects and patients with pulmonary disorders.

Main Methods:

• A model was developed utilizing 129Xe ventilated volume (VV), barrier uptake, and RBC transfer measurements.
• Accessible alveolar volume (VA) was estimated from VV using a scaling factor (kV).
• Membrane and capillary blood volume-specific conductance coefficients (kB and kR) were derived from normalized barrier uptake and RBC transfer, respectively.
• Image-derived DLCO was calculated by multiplying estimated VA by the transfer coefficient (KCO).

Main Results:

• The model demonstrated strong correlation (R² = 0.75, P < 0.001) between 129Xe-derived DLCO and measured DLCO values across 142 subjects (41 healthy, 101 patients).
• This strong correlation was consistent within individual disease cohorts.
• Specific scaling factors were determined: kV = 1.47 [1.42, 1.52], kB = 10.6 [8.6, 13.6] mL/min/mmHg/L, and kR = 13.6 [11.4, 16.7] mL/min/mmHg/L.

Conclusions:

• Hyperpolarized 129Xe MRI can effectively estimate the individual components contributing to DLCO, including VA, membrane, and capillary blood volume.
• This imaging-derived DLCO provides a spatially resolved and physiologically interpretable assessment of gas exchange.
• The model enables independent and regional monitoring of ventilation, barrier function, and capillary blood flow in pulmonary diseases.