Magnetization-transfer flow-independent dark-blood delayed enhancement cardiac MRI optimizes discrimination of ST-elevation myocardial infarct borders.

Objectives: To prospectively compare image quality and infarct sizing methods between magnetization-transfer "flow-independent dark-blood delayed enhancement" (MT-FIDDLE) and standard "bright-blood"-late gadolinium enhancement (LGE) cardiac-magnetic-resonance (CMR) sequence.

Methods: "Bright-blood"-LGE and MT-FIDDLE sequence were acquired in 110 patients at 4 days (n = 33), 4 months (n = 39) and 12 months (n = 38) after acute ST-elevation myocardial infarction (STEMI). Subjective image quality, including confidence in infarct segmentation and blood-pool bordering, were each rated on a 4-point Likert scale. Objective image quality was assessed by the detectability index (DI). Infarct volumes derived via full-width at half-maximum (FWHM) and different number of standard deviations ("n-SD") methods on MT-FIDDLE images were compared with FWHM and reference 5-SD results from "bright-blood-LGE images.

Results: Overall subjective median image quality was excellent for both LGE sequences. Qualitative analysis revealed a significantly higher confidence in infarct segmentation and in blood-pool bordering for MT-FIDDLE as compared to "bright-blood"-LGE (all p < 0.001). Infarct volumes assessed by the FWHM technique on MT-FIDDLE and "bright-blood"-LGE showed excellent agreement overall (Concordance correlation coefficient, CCC = 0.96). The 3-SD technique for MT-FIDDLE showed the best agreement with the 5-SD method for "bright-blood"-LGE overall (CCC = 0.94), as well as in the subgroup with excellent confidence in infarct segmentation on "bright-blood"-LGE (CCC = 0.96). DI of scar versus LV blood-pool was higher for MT-FIDDLE (8.9 ± 5.5) compared to "bright-blood"-LGE sequence (2.0 ± 1.5; p < 0.001).

Conclusion: MT-FIDDLE significantly optimizes the discrimination between myocardial infarction and adjacent blood-pool in STEMI patients. As compared to the established 5-SD technique on "bright-blood"-LGE, the 3-SD method on MT-FIDDLE results in consistent infarct volumes.

Key points: Question Does magnetization-transfer "flow-independent dark-blood delayed enhancement" (MT-FIDDLE) offer any benefits over standard "bright-blood"-late gadolinium enhancement (LGE) cardiac-magnetic-resonance (CMR) for identifying STEMI infarct borders? Findings MT-FIDDLE image quality was higher than LGE CMR and measured infarct volume comparability to the standard 5-SD-threshold-technique. Clinical relevance MT-FIDDLE facilitates the assessment of myocardial infarctions at the subendocardial border, improving the discrimination between myocardial infarction and adjacent blood-pool in STEMI patients.