SCMR 22nd Annual Scientific Sessions
Background: T1-rho is the spin-lattice relaxation time measured using a long continuous spin-lock RF pulse, which is applied aligned with the spins. Native T1-rho mapping is sensitive to low-frequency interactions between water and macromolecules and may be an attractive technique for detection of myocardial interstitial fibrosis without the need for exogenous contrast agents1.
Between January 2015 and January 2017, we enrolled 219 patients [87 F, 132 M; mean age 48±18] referred for evaluation of suspected or known non-ischemic cardiomyopathies. The study was approved by the medical ethics committee and written informed consent was obtained from all participants. All patients underwent T1-rho mapping on a 1.5T clinical MR system (Ingenia, Software Release 5.1.7, Philips Healthcare) using the following imaging parameters: TR/TE, 3.5/1.75 ms; flip angle, 35 degrees; BW/pixel, 723 Hz; FOV, 288 x 288 mm2; slice thickness, 8.0 mm; in-plane spatial resolution: 2.0 x 2.0 mm2; SENSE parallel imaging factor 2; 8 startup echoes and spin-lock amplitude of 500 Hz. Acquisition time was 3 breath holds (approximately 45 s in total). After the acquisition was completed T1-rho images were transferred to a dedicated workstation for motion correction and standardized post-processing. Results of T1-rho mapping were compared with the results of native and post-contrast T1 mapping as well as extracellular volume fraction (ECV) measurements. Spearman correlation coefficients were calculated to determine the correlation between ECV and whole heart T1-rho values, native T1-values and post-contrast T1-values.
T1-rho and ECV maps were successfully obtained in all 211 patients. 189 datasets were of sufficient quality for automatic processing. Mean T1-rho relaxation time was 64.0 ± 5.0 ms. Mean native T1 was 1094 ± 56 ms, mean post-contrast T1 was 390 ± 58 ms. ECV values ranged between 5-47%, with a mean value of 25.2 ± 8.0%]. A strong and significant correlation was found between T1-rho relaxation time and ECV fraction (Spearman coefficient: 0.63, p<0.001, left figure panel). Weak correlations were found between native T1 and ECV fraction (0.31, p<0.001, middle figure panel), and post-contrast T1 (-0.26, p<0.01, right figure panel).
Native T1-rho is strongly correlated with ECV and thus provides information on diffuse myocardial fibrosis without the need for injection of exogenous contrast agents.