Cardiac quantitative susceptibility mapping (QSM) for heart chamber oxygenation

Area of Science:

• Medical Imaging
• Biophysics
• Cardiovascular Physiology

Background:

• Quantitative susceptibility mapping (QSM) is an emerging MRI technique.
• Accurate measurement of mixed-venous oxygen saturation (SvO2) is clinically important.
• Non-invasive methods for SvO2 assessment in cardiac MRI are desirable.

Purpose of the Study:

• To establish the feasibility of in vivo cardiac QSM.
• To demonstrate non-invasive SvO2 measurement using cardiac QSM.
• To correlate QSM-derived SvO2 with blood oxygen levels.

Main Methods:

• 1.5T ECG-gated multi-echo 2D gradient echo data acquisition.
• Iterative phase unwrapping and fat suppression (IDEAL) for artifact removal.
• Preconditioned dipole inversion for wide susceptibility range and SvO2 calculation from RV/LV blood susceptibility differences.

Main Results:

• Interpretable cardiac QSM was achieved in 64% of healthy volunteers.
• Significant contrast observed between right ventricle (RV) and left ventricle (LV) blood susceptibility.
• RV blood susceptibility values correlated with an SvO2 of 78.3 ± 2.3%.

Conclusions:

• In vivo cardiac QSM is feasible for non-invasive SvO2 measurement.
• QSM demonstrates potential for assessing cardiac blood oxygenation.
• Further improvements in data acquisition are needed for broader clinical application.