MOLLI and AIR T sub(1) mapping pulse sequences yield different myocardial T sub(1) and ECV measurements

• Published in: NMR in biomedicine Vol. 27; no. 11; pp. 1419 - 1426
• Main Authors: Hong, KyungPyo, Kim, Daniel
• Format: Journal Article
• Language: English
• Published: 01.11.2014
• ISSN: 0952-3480; 1099-1492
• DOI: 10.1002/nbm.3221

Both post-contrast myocardial T sub(1) and extracellular volume (ECV) have been reported to be associated with diffuse interstitial fibrosis. Recently, the cardiovascular magnetic resonance (CMR) field is recognizing that post-contrast myocardial T sub(1) is sensitive to several confounders and migrating towards ECV as a measure of collagen volume fraction. Several recent studies using widely available Modified Look-Locker Inversion-recovery (MOLLI) have reported ECV cutoff values to distinguish between normal and diseased myocardium. It is unclear if these cutoff values are translatable to different T sub(1) mapping pulse sequences such as arrhythmia-insensitive-rapid (AIR) cardiac T sub(1) mapping, which was recently developed to rapidly image patients with cardiac rhythm disorders. We sought to evaluate, in well-controlled canine and pig experiments, the relative accuracy and precision, as well as intra- and inter-observer variability in data analysis, of ECV measured with AIR as compared with MOLLI. In 16 dogs, as expected, the mean T sub(1) was significantly different (p<0.001) between MOLLI (891 plus or minus 373ms) and AIR (1071 plus or minus 503ms), but, surprisingly, the mean ECV between MOLLI (21.8 plus or minus 2.1%) and AIR (19.6 plus or minus 2.4%) was also significantly different (p<0.001). Both intra- and inter-observer agreements in T sub(1) calculations were higher for MOLLI than AIR, but intra- and inter-observer agreements in ECV calculations were similar between MOLLI and AIR. In six pigs, the coefficient of repeatability (CR), as defined by the Bland-Altman analysis, in T sub(1) calculation was considerably lower for MOLLI (32.5ms) than AIR (82.3ms), and the CR in ECV calculation was also lower for MOLLI (1.8%) than AIR (4.5%). In conclusion, this study shows that MOLLI and AIR yield significantly different T sub(1) and ECV values in large animals and that MOLLI yields higher precision than AIR. Findings from this study suggest that CMR researchers must consider the specific pulse sequence when translating published ECV cutoff values into their own studies. Copyright copyright 2014 John Wiley & Sons, Ltd. The purpose of this study was to evaluate, in well-controlled canine and pig experiments, the relative accuracy and precision of AIR cardiac T1 mapping compared with widely available MOLLI cardiac T1 mapping. In 16 canines, mean T1 was significantly different (p < 0.001) between MOLLI (891.8 plus or minus 373 ms) and AIR (1071 plus or minus 503 ms), as well as mean ECV (p < 0.001) between MOLLI (21.8 plus or minus 2.1%) and AIR (19.6 plus or minus 2.4%). In 6 pigs, the coefficient of repeatability (CR), as defined by the Bland-Altman analysis, of T1 was considerably lower for MOLLI (32.5 ms) than AIR (82.3 ms), and the CR of ECV was also lower for MOLLI (1.8%) than AIR (4.5%). In conclusion, this study shows that MOLLI and AIR yield significantly different T1 and ECV values in large animals and that MOLLI yields higher precision than AIR. Findings from this study suggest that CMR researchers must consider the specific pulse sequence when translating published ECV cutoff values into their own studies.