Role of endogenous T1ρ and its dispersion imaging in differential diagnosis of cardiac amyloidosis

Background: Cardiovascular magnetic resonance (CMR) has demonstrated excellent performance in the diagnosis of cardiac amyloidosis (CA). However, misdiagnosis occasionally occurs because the morphological and functional features of CA are non-specific. This study was performed to determine the value of non-contrast CMR T1 rho in the diagnosis of CA. Methods: This prospective study included 45 patients with CA, 30 patients with hypertrophic cardiomyopathy (HCM), and 10 healthy controls (HCs). All participants underwent cine (whole heart), T1 rho mapping, pre- and post-contrast T1 mapping imaging (three slices), and late gadolinium enhancement using a 3T whole-body magnetic resonance imaging system. All participants underwent T1 rho at two spin-locking frequencies: 0 and 298 Hz. Extracellular volume (ECV) maps were obtained using pre- and post-contrast T1 maps. The myocardial T1 rho dispersion map, termed myocardial dispersion index (MDI), was also calculated. All parameters were measured in the left ventricular myocardial wall. Participants in the HC group were scanned twice on different days to assess the reproducibility of T1 rho measurements. Results: Excellent reproducibility was observed upon evaluation of the coefficient of variation between two scans (T1 rho [298 Hz]: 3.1%; T1 rho [0 Hz], 2.5%). The ECV (HC: 27.4 +/- 2.8% vs HCM: 32.6 +/- 5.8% vs CA: 46 +/- 8.9%; p < 0.0001), T1 rho [0 Hz] (HC: 35.8 +/- 1.7 ms vs HCM: 40.0 +/- 4.5 ms vs CA: 51.4 +/- 4.4 ms; p < 0.0001) and T1 rho [298 Hz] (HC: 41.9 +/- 1.6 ms vs HCM: 48.8 +/- 6.2 ms vs CA: 54.4 +/- 5.2 ms; p < 0.0001) progressively increased from the HC group to the HCM group, and then the CA group. The MDI progressively decreased from the HCM group to the HC group, and then the CA group (HCM: 8.8 +/- 2.8 ms vs HC: 6.1 +/- 0.9 ms vs CA: 3.4 +/- 2.1 ms; p < 0.0001). For differential diagnosis, the combination of MDI and T1 rho [298 Hz] showed the greatest sensitivity (98.3%) and specificity (95.5%) between CA and HCM, compared with the native T1 and ECV. Conclusion: The T1 rho and MDI approaches can be used as non-contrast CMR imaging biomarkers to improve the differential diagnosis of patients with CA.