Native T1 and Extracellular Volume Measurements by Cardiac MRI in Healthy Adults: A Meta-Analysis.

Purpose To summarize the literature by performing a systematic review and pooled analysis of the data, to understand the extent of variability among studies of native T1 and extracellular volume (ECV) measurements, and to identify covariates that account for heterogeneity between studies. Materials and Methods PubMed, Web of Science, and Cochrane Central were searched for native T1 and ECV measurements of the left ventricle in health adult study participants. The search terms used were "T1 mapping heart," "Native T1 heart," and "ECV heart." Summary means were generated with random-effects modeling. Heterogeneity was assessed by using the inconsistency factor (I 2). Subgroup analyses and meta-regression analyses were conducted to identify etiologic causes of heterogeneity. Results This systematic review of native T1 included 120 articles, with 5541 participants (mean age, 50 years; 51.0% men [2826 of 5541]). The pooled mean of native T1 was 976 msec (95% confidence interval [CI]: 969 msec, 983 msec) at 1.5 T and 1159 msec (95% CI: 1143 msec, 1175 msec) at 3.0 T. I 2 was 99% at both field strengths. Eighty-one articles were included in the systematic review of ECV, with 3872 participants (mean age, 52 years; 50.0% men [1936 of 3872]). The pooled mean of ECV was 25.9% at field strength of 1.5 T (95% CI: 25.5%, 26.3%) and 3.0 T (95% CI: 25.4%, 26.5%). I 2 was 94% and 90% at 1.5 and 3.0 T, respectively. Conclusion The pooled means of extracellular volume and native T1 measurements in healthy adult participants are summarized in this analysis. There was significant heterogeneity found among studies, highlighting the importance of standardized cardiac MRI protocols and the derivation of institution specific reference ranges. © RSNA, 2018 Online supplemental material is available for this article. See also the editorial by Dodd and Dewey in this issue.