Full Title:Reference values for healthy human myocardium using a T1 mapping methodology: results from International T1 Multicenter CMR study
Short title:Multicenter T1 mapping study: normal reference values
First authors: Darius Dabir, Nicholas Child
Authors:
Darius Dabir1, MD; Nicholas Child1, MD; AshwinKalra, BSc; Toby Rogers1, BM BCh, MA; Rolf Gebker2 MD, PhD; Andrew Jabbour3, MD, PhD; Sven Plein4; MD, PhD; Chung-Yao Yu3; MBBS, James Otton3, MBBS, PhD; Ananth Kidambi4, MD, PhD; Adam McDiarmid4, MD, PhD; David Broadbent4, PhD; David M. Higgins5, PhD; Bernhard Schnackenburg6, PhD; Lucy Foote1, BSc; Ciara Cummins1, MSc, Eike Nagel1, MD, PhD; Valentina O. Puntmann1*, MD, PhD
Methods
Image acquisition
All cine-images were acquired using a balanced steady-state free precession sequence in combination with parallel imaging (SENSitivity Encoding, factor 2) and retrospective gating during a gentle expiratory breath- hold (TE/TR/flip-angle: 1.7msec/3.4msec/60°, acquired spatial resolution 1.8x1.8x8 mm). LGE imaging was performed in a gapless whole heart coverage of short axis slices ~20 minutes after administration of gadobutrol using a mid-diastolic inversion prepared 2-dimensional gradient echo sequence (TE/TR/flip-angle 2.0 msec/3.4 msec/25°, acquired spatial resolution 1.8x1.8x8 mm) with a patient-adapted prepulse delay.
Image analysis
Endocardial LV borders were manually traced at end-diastole and end-systole. The papillary muscles were included as part of the LV cavity volume. LV end-diastolic (EDV) and end-systolic (ESV) volumes were determined using Simpson’s rule. Ejection fraction (EF) was computed as EDV-ESV/EDV. All volumetric indices were normalized to body surface area (BSA). LGE images were visually examined for the presence of regional fibrosis showing as bright areas within the myocardium in corresponding longitudinal views and by exclusion of potential artifacts [6].
Results
Inter- and intraobserver reproducibility
In a mixed sample of 10 subjects from all centers (see above), intra-observer reproducibility for both field strengths septal measurements showed better agreement and lower coefficient of variation (CoV) for native T1 measurements compared to postcontrast T1 measurements, and for septal T1 measurements compared to coverage of complete SAX slice.
Native T1 of septal myocardium (for both field strengths, Figure 3) showed excellent intra-observer (r=0.98, p<0.01, MD±SD=-2.1±4.3, CoV=5.2%) and inter-observer (r=0.96, p <0.01, MD±SD=1.3±6.8; CoV=6.1) agreement for all subjects, whereas postcontrast T1 measurements showed slightly lower intra-observer (r=0.91, p <0.01, MD±SD=-4.8±7.2, CoV=12.6%) and inter-observer (r=0.87, p <0.01; MD±SD=-5.9±9.8; CoV=16.2%) agreement.
Native T1 of complete SAX slice myocardium showed reasonable intra-observer and inter-observer reproducibility (native T1 (SAX): intraobserver: r=0.81, p<0.01; MD±SD=-7.1±9.2; CoV: 5.9%; interobserver: r=0.74, p<0.01; MD±SD=-8.3±.11.2; CoV: 7.2%), whereas postcontrast T1 measurements showed lower intra-observer and inter-observer reproducibility (postcontrast T1 (SAX): intraobserver: r=0.78, p<0.01; MD±SD=-8.9±.14.3; CoV: 10.1%; interobserver: r=0.69, p<0.01; MD±SD=-15.2±.19.3; CoV: 7.3%).