Optimizing reliability of RBC signal oscillation measures from hyperpolarized 129Xe MRI

Area of Science:

• Pulmonary Medicine
• Medical Imaging
• Cardiovascular Research

Background:

• Gas exchange hyperpolarized 129Xe MRI (Xe-MRI) detects cardiogenic oscillations in red blood cell (RBC) signals, indicating sensitivity to pulmonary disease.
• Generating regional oscillation amplitude maps via keyhole image reconstruction is possible but validation is hindered by a lack of pulmonary microvascular health biomarkers.
• Varied methodologies in previous Xe-MRI implementations obscure optimal techniques for measuring regional oscillation amplitude.

Purpose of the Study:

• To evaluate and compare different published methods for Xe-MRI oscillation mapping to determine which offers the best same-day reliability.
• To establish reliability as a surrogate endpoint for validating Xe-MRI oscillation maps' sensitivity to pulmonary physiology, given the absence of direct microvascular health biomarkers.
• To demonstrate "healthy" oscillation amplitude maps using data from healthy volunteers.

Main Methods:

• Assessed same-day reliability of RBC oscillation measures in patients with systemic sclerosis (N=6) and pulmonary arterial hypertension (PAH, N=10).
• Utilized single-time-point data from healthy volunteers (N=9) to generate reference "healthy" oscillation amplitude maps.
• Compared reliability across different published oscillation mapping methodologies, including those generating both amplitude and phase information.

Main Results:

• Global RBC oscillation amplitude measures demonstrated strong reliability (Intraclass Correlation Coefficient, ICC=0.88), comparable to standard Xe-MRI measures (ICC≥0.82).
• Overall means for regional oscillation mapping showed strong reliability (ICC≥0.86), despite some inter-scan disagreement in regional features.
• Advanced oscillation amplitude mapping techniques providing both amplitude and phase yielded maps equivalent to amplitude-only methods.

Conclusions:

• Optimized Xe-MRI oscillation mapping exhibits robust reliability, even in individuals with pulmonary disease.
• The findings support the use of Xe-MRI oscillation mapping as a reliable tool for assessing pulmonary microvascular function.
• Methodological standardization is crucial for maximizing the reliability and clinical utility of Xe-MRI oscillation mapping.