Role of T1 mapping as a complementary tool to T2* for non-invasive cardiac iron overload assessment

Abstract

BackgroundIron overload-related heart failure is the principal cause of death in transfusion dependent patients, including those with Thalassemia Major. Linking cardiac siderosis measured by T2* to therapy improves outcomes. T1 mapping can also measure iron; preliminary data suggests it may have higher sensitivity for iron, particularly for early overload (the conventional cut-point for no iron by T2* is 20ms, but this is believed insensitive). We compared T1 mapping to T2* in cardiac iron overload.MethodsIn a prospectively large single centre study of 138 Thalassemia Major patients and 32 healthy controls, we compared T1 mapping to dark blood and bright blood T2* acquired at 1.5T. Linear regression analysis was used to assess the association of T2* and T1. A “moving window” approach was taken to understand the strength of the association at different levels of iron overload.ResultsThe relationship between T2* (here dark blood) and T1 is described by a log-log linear regression, which can be split in three different slopes: 1) T2* low, <20ms, r2 = 0.92; 2) T2* = 20-30ms, r2 = 0.48; 3) T2*>30ms, weak relationship. All subjects with T2*<20ms had low T1; among those with T2*>20ms, 38% had low T1 with most of the subjects in the T2* range 20-30ms having a low T1.ConclusionsIn established cardiac iron overload, T1 and T2* are concordant. However, in the 20-30ms T2* range, T1 mapping appears to detect iron. These data support previous suggestions that T1 detects missed iron in 1 out of 3 subjects with normal T2*, and that T1 mapping is complementary to T2*. The clinical significance of a low T1 with normal T2* should be further investigated.

Simultaneous proton density fat‐fraction and imaging with water‐specific T1 mapping (PROFIT1): application in liver

“… mapping provides important complimentary information for the interpretation the T 1(Water) in the liver. The correlations between T 1(Water) and observed in the current study were expected and their relationships with iron concentrations in the liver 22,23 and heart 36 have previously been characterized. Specifically, the large range of T 1(Water) values observed within the healthy subjects likely reflects higher iron concentration in those with lower T 1 values.…”

Cardiovascular magnetic resonance (CMR) in restrictive cardiomyopathies

“…In addition, in patients with only mild increases in cardiac iron, nT1 showed a superior reproducibility as compared to T2* measurements (about 2.5-7 fold T2*) [47].…”

Cardiac magnetic resonance T1 mapping. Part 2: Diagnostic potential and applications

“…Early recognition of myocardial diseases helps to optimize patients' treatment and outcome. Substantially decreased native T1 times have been reported in early stages of Anderson-Fabry disease (AFD) [49,50] and patients with cardiac iron overload [51,52], enabling differentiation from normal myocardium prior to the development of structural, functional, or electrical abnormalities. Compared to T2* mapping, native T1 reveals higher sensitivities for the diagnosis of myocardial iron loading at 1.5 T and 3 T at early stages of disease [51,52].…”

“…Substantially decreased native T1 times have been reported in early stages of Anderson-Fabry disease (AFD) [49,50] and patients with cardiac iron overload [51,52], enabling differentiation from normal myocardium prior to the development of structural, functional, or electrical abnormalities. Compared to T2* mapping, native T1 reveals higher sensitivities for the diagnosis of myocardial iron loading at 1.5 T and 3 T at early stages of disease [51,52]. Increased native T1 and ECV values have been reported in early stages of cardiac amyloidosis [53], genotype-positive dilated cardiomyopathy (DCM) [54,55], hypertrophic cardiomyopathy (HCM) sarcomere-gene mutations carriers [56], and asymptomatic patients with valvular diseases [57,58].…”