Endogenous assessment of chronic myocardial infarction with T1ρ-mapping in patients.

Background: Detection of cardiac fibrosis based on endogenous magnetic resonance (MR) characteristics of the myocardium would yield a measurement that can provide quantitative information, is independent of contrast agent concentration, renal function and timing. In ex vivo myocardial infarction (MI) tissue, it has been shown that a significantly higher T_1ρ is found in the MI region, and studies in animal models of chronic MI showed the first in vivo evidence for the ability to detect myocardial fibrosis with native T_1ρ-mapping. In this study we aimed to translate and validate T1ρ-mapping for endogenous detection of chronic MI in patients. Methods: We first performed a study in a porcine animal model of chronic MI to validate the implementation of T_1ρ-mapping on a clinical cardiovascular MR scanner and studied the correlation with histology. Subsequently a clinical protocol was developed, to assess the feasibility of scar tissue detection with native T_1ρ-mapping in patients (n = 21) with chronic MI, and correlated with gold standard late gadolinium enhancement (LGE) CMR. Four T_1ρ-weighted images were acquired using a spin-lock preparation pulse with varying duration (0, 13, 27, 45 ms) and an amplitude of 750 Hz, and a T_1ρ-map was calculated. The resulting T_1ρ-maps and LGE images were scored qualitatively for the presence and extent of myocardial scarring using the 17-segment AHA model. Results: In the animal model (n = 9) a significantly higher T1ρ relaxation time was found in the infarct region (61 ± 11 ms), compared to healthy remote myocardium (36 ± 4 ms) . In patients a higher T1ρ relaxation time (79 ± 11 ms) was found in the infarct region than in remote myocardium (54 ± 6 ms). Overlap in the scoring of scar tissue on LGE images and T_1ρ-maps was 74%. Conclusion: We have shown the feasibility of native T1ρ-mapping for detection of infarct area in patients with a chronic myocardial infarction. In the near future, improvements on the T1ρ -mapping sequence could provide a higher sensitivity and specificity. This endogenous method could be an alternative for LGE imaging, and provide additional quantitative information on myocardial tissue characteristics. [ABSTRACT FROM AUTHOR]