Reference values for healthy human myocardium using a T1 mapping methodology: results from the International T1 Multicenter cardiovascular magnetic resonance study

Abstract

Background: T1 mapping is a robust and highly reproducible application to quantify myocardial relaxation of longitudinal magnetisation. Available T1 mapping methods are presently site and vendor specific, with variable accuracy and precision of T1 values between the systems and sequences. We assessed the transferability of a T1 mapping method and determined the reference values of healthy human myocardium in a multicenter setting.

Methods: Healthy subjects (n=102; mean age 41 years (range 17-83), male, n=53 (52%)), with no previous medical history, and normotensive low risk subjects (n=113) referred for clinical cardiovascular magnetic resonance (CMR) were examined. Further inclusion criteria for all were absence of regular medication and subsequently normal findings of routine CMR. All subjects underwent T1 mapping using a uniform imaging set-up (modified Look- Locker inversion recovery, MOLLI, using scheme 3(3)3(3)5)) on 1.5 Tesla (T) and 3 T Philips scanners. Native T1-maps were acquired in a single midventricular short axis slice and repeated 20 minutes following gadobutrol. Reference values were obtained for native T1 and gadolinium-based partition coefficients, λ and extracellular volume fraction (ECV) in a core lab using standardized postprocessing.

Results: In healthy controls, mean native T1 values were 950±21 msec at 1.5 T and 1052±23 at 3 T. λ and ECV values were 0.44±0.06 and 0.25±0.04 at 1.5 T, and 0.44±0.07 and 0.26±0.04 at 3 T, respectively. There were no significant differences between healthy controls and low risk subjects in routine CMR parameters and T1 values. The entire cohort showed no correlation between age, gender and native T1. Cross-center comparisons of mean values showed no significant difference for any of the T1 indices at any field strength. There were considerable regional differences in segmental T1 values. λ and ECV were found to be dose dependent. There was excellent inter- and intraobserver reproducibility for measurement of native septal T1.

Conclusion: We show transferability for a unifying T1 mapping methodology in a multicenter setting. We provide reference ranges for T1 values in healthy human myocardium, which can be applied across participating sites.

Figure 1

Illustration of T1 measurements by ROI placements in septal myocardium (A), blood pool (B), and by coverage of myocardium in short axis slice (SAX) (C).

Figure 2

Concordance of T1 values and routine CMR measures between healthy volunteers (n = 102) and a subgroup of patients with low pretest likelihood of cardiovascular disease (n = 113).

Figure 3

Segmental variations of T1 values in midventricular short axis slice (SAX, segments 7–12) at 1.5 T and 3 T field strengths. Bull’s eye with annotated segments in midventricular SAX slice.

Figure 4

Concordance between measurements obtained at core lab and at participating sites for native and postcontrast septal and short axis slice (SAX) measurements in a random sample of 9 cases from all sites (KCL – King’s College London, Leeds – University of Leeds, DHZB – Deutsches Herzzentrum Berlin (German Heart Institute Berlin), Sydney – Vincent University, Sydney Australia.

Figure 5

Distribution of native T1 values for age and gender. Age groups were determined by separating the entire study population into quartiles (group 1: ≤30 years (1.5 T, n = 27, 3 T = 26), group 2: 31 and 42 years (1.5 T, n = 28, 3 T = 27); group 3: 42 and 53 years (1.5 T, n = 27, 3 T = 24), group 4: ≥ 53 years (1.5 T, n = 28; 3 T = 28).

Figure 6

Relationship between native T1 and age separately for field strengths.

Figure 7

Interobserver and intraobserver reproducibility of native T1 values.