To develop a breath-hold cardiac quantitative susceptibility mapping (QSM) sequence for noninvasive measurement of differential cardiac chamber blood oxygen saturation (ΔSO2). A non-gated three-dimensional stack-of-spirals QSM sequence was implemented to continuously sample the data throughout the cardiac cycle. Measurements of ΔSO2 between the right and left heart chamber obtained by the proposed sequence and a previously validated navigator Cartesian QSM sequence were compared in three cohorts consisting of healthy volunteers, coronavirus disease 2019 survivors, and patients with pulmonary hypertension. In the pulmonary-hypertension cohort, Bland-Altman plots were used to assess the agreement of ΔSO2 values obtained by QSM and those obtained by invasive right heart catheterization (RHC). Compared with navigator QSM (average acquisition time 419 ± 158 s), spiral QSM reduced the scan time on average by over 20-fold to a 20-s breath-hold. In all three cohorts, spiral QSM and navigator QSM yielded similar ΔSO2. Among healthy volunteers and coronavirus disease 2019 survivors, ΔSO2 was 17.41 ± 4.35% versus 17.67 ± 4.09% for spiral and navigator QSM, respectively. In pulmonary-hypertension patients, spiral QSM showed a slightly smaller ΔSO2 bias and narrower 95% limits of agreement than that obtained by navigator QSM (1.09% ± 6.47% vs. 2.79% ± 6.99%) when compared with right heart catheterization. Breath-hold three-dimensional spiral cardiac QSM for measuring differential cardiac chamber blood oxygenation is feasible and provides values in good agreement with navigator cardiac QSM and with reference right heart catheterization.
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