Effects of supplemental oxygen on cardiovascular magnetic resonance water proton relaxation time constant measurements (T1, T2 and T2*)

Abstract

ObjectiveTo study, the effects of supplemental oxygen on the measurement of native cardiovascular water proton relaxation time constants using commercially available protocols. MethodsT1, T2 and T2* relaxation time constant mapping were performed in twelve volunteers at 1.5 T breathing room air and supplemental oxygen supplied by nasal cannula and a non-rebreather mask. Regions-of-interest were drawn for quantitative measurements in the bloodpool of each ventricle and atria as well as septal myocardium. The effects of supplemental oxygen were investigated statistically using a mixed model analysis of variance. Intra- and inter-observer reproducibility were assessed using the Intraclass Correlation Coefficient and Coefficient of Variation. ResultsBlood T1 relaxation time constants in the left ventricle (T1 change = −241.0 ms) and left atrium (T1 change = −247.0 ms) decreased significantly in every subject after oxygen inhalation with a non-rebreather mask (p < 0.001). No significant changes of T1 in the right side of the heart were detected after oxygen inhalation with the non-rebreather mask (p = 0.345). Oxygen inhalation with nasal cannula did not significantly change blood T1 in the study (p = 0.497). No significant changes in myocardial T1 (p = 0.390), T2 (p = 0.960) or T2* (p = 0.438) were observed with supplemental oxygen supplied by nasal cannula or the non-rebreather mask. Results were similar in mid-short-axis and horizontal long-axis acquisitions. ConclusionSupplemental oxygen does not affect myocardial relaxation time constant measurements with current protocols. On the other hand, blood T1 measurements with the inhalation of supplemental oxygen supplied by a non-rebreather mask change significantly and could affect myocardial tissue characterization if used for the calculation of extracellular volume. Additionally, current relaxation time constant mapping protocols do not reproducibly detect myocardial T1 changes with supplemental oxygen inhalation.