Precision-optimized single protocol pre-/post-contrast modified-look locker inversion T1 mapping using composite inversion group fitting

Precision-optimized single protocol pre-/post-contrast modified-look locker inversion T1 mapping using composite inversion group fitting:



Publication date: Available online 1 October 2020

Source: Magnetic Resonance Imaging

Author(s): Luigia D'Errico, Marshall S. Sussman, Kate Hanneman, Bernd J. Wintersperger




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Magnetic Resonance Imaging
Available online 1 October 2020
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Original ContributionPrecision-optimized single protocol pre-/post-contrast modified-look locker inversion T1 mapping using composite inversion group fitting
Author links open overlay panelLuigiaD'ErricoabMarshall S.SussmanabKateHannemanabBernd J.WinterspergerabShow more
https://doi.org/10.1016/j.mri.2020.09.025Get rights and content


Abstract

Background

Investigation of a simple, precision optimized, identical pre−/post-contrast modified look locker inversion recovery (MOLLI) protocol employing Composite inversion group (IG) fitting in a clinical cardiomyopathy population.

Methods

Cardiac magnetic resonance imaging (MRI) was performed at 3 Tesla in 36 patients (48.0 years [IQR: 35.7, 58.2 years]) with known/suspicion of hypertrophic cardiomyopathy. T1 mapping was performed pre−/post-contrast (0.15 mmol/kg Gadobutrol) using a standard 3-parameter fit (STANDARD) and an optimized (OPTIMAL) single-protocol Composite-IG fitting MOLLI approach. The OPTIMAL protocol was based on a simulation study (for 11hb acquisitions) with cost metric analysis across the range of expected T1 values (300-1400 ms) and heart rates (50-80 bpm).

All maps were generated offline based on motion corrected source images. Based on region of interest analysis, the precision of both approaches was assessed using a previously validated propagation of errors technique for pre−/post-contrast T1 mapping as well as calculated ECV (based on point-of care hematocrit measurements. Furthermore, respective T1 and ECV values were calculated. Statistical methods included Wilcoxon Signed-Rank tests and Student's paired t-test.

Results

A total of ~9000 11hb inversion groupings were simulated with a 4(0)2(0)2(0)2(0)1 grouping providing the optimal precision across the specified T1/heart rate range. In comparison to standard pre-contrast 5(3)3 MOLLI, this OPTIMAL protocol demonstrated a significantly improved pre-contrast precision (9.1 [6.2, 9.9]ms vs. 9.4 [7.3, 10.8]ms; P < 0.001) while no significant differences were found for post-contrast T1 mapping (4.5 [2.6, 5.3]ms vs. 4.2 [2.8, 5.1]ms; P = 0.25) and EVC mapping (0.38 [0.28, 0.45]ms vs. 0.35 [0.25, 0.44]ms; P = 0.07) or reproducibility (0.16 [0.14, 0.19] vs. 0.19 [0.13, 0.23] P = 0.53).

Direct comparison of resulting T1/ECV values demonstrated no significant differences between STANDARD and OPTIMAL techniques for pre-contrast T1 (1178 [1158, 1199]ms vs. 1173 [1143, 1195]ms; P = 0.46) and significant differences for post-contrast T1 (466 [446, 506]ms vs. 456 [433, 503]ms; P = 0.04) and ECV (23.1 [20.8, 25.1]% vs. 23.9 [22.3, 26.4]%; P = 0.001).

Conclusions

A single optimized Composite-IG fitting protocol for pre−/post-contrast T1 mapping demonstrated improved precision over standard MOLLI techniques. It enables a simplified workflow with reduction of potential sources of error especially with respect to image data co-registration easing advanced post-processing for generation of patient specific ECV maps.

Keywords
Magnetic resonance imaging
Cardiomyopathies
Myocardium
Fibrosis
Precision

Abbreviations
BSA
body surface area.
MRI
magnetic resonance imaging.
ECV
extracellular volume fraction.
EDVi
end-diastolic volume index.
ESVi
end-systolic volume index.
EF
ejection fraction.
FoV
field-of-view.
GBCA
gadolinium-based contrast agents.
GRAPPA
generalized autocalibrating partial parallel acquisition.
Hb
hemoglobin.
Hct
hematocrit.
IQR
interquartile range.
IG
inversion group.
LGE
late gadolinium enhancement.
LV
left ventricle.
MASSi
myocardial mass index.
MOLLI
modified look-locker inversion recovery.
ROI
region of interest.
SSFP
steady state free precession.
bSSFP
balanced steady state free precession.