The multiecho sequence parameters will be as follows: for the measurement more of myocardial T2*, a single short axis mid-ventricular will be acquired at 10 echo times (1.99–20.26 ms, which will increase in 2.03 ms increments) in a single breath-hold. A gradient-echo sequence will be used with a flip angle of 20°, a matrix of 90–256 pixels, a field of view of 40 cm, and a sampling bandwidth of 814 Hz per pixel. The TR in between the 10 radio frequency pulses applied to each cardiac cycle will be 22.17 ms. A homogeneous full-thickness region of interest (ROI) will be chosen in the LV septum, encompassing
both epicardial and endocardial regions. The signal intensity of this region will be measured for each image using QMass V.7.6, MEDIS software, and will then be plotted against the echo time to form an exponential decay curve. To derive T2*, an exponential trend line
will be fitted with an equation in the form y Ke–TE/T2* where K represents a constant, TE represents the echo time and y represents the image signal intensity. Given the known risk of sideroblastic cardiomyopathy in the hearts of patients with thalassaemia, we expect our T2* values to reflect this myocardial iron load as substantially shorter (4–10 ms) values. These values can potentially lead to a rapid decay in signal intensity with the signals of later echocardiography images buried in the background noise and motion. Therefore, in order to make the best-fit curve, we will employ the truncation method as described in the literature,34 which will exclude all data points less than a particular SNR, generated according to the algorithm described by Bonny et al.35 For all practical purposes, as utilised in the literature, we will therefore remove data points <2 SNR in our study for short T2* values. Figure 1 demonstrates the practical application of the truncation model to account for background noise. Figure 1 Adapted from Carpenter et al. This graph shows signal intensity (arbitrary units) plotted against echocardiography
time (milliseconds) for the hearts shown on top. Heart 1 (with normal iron levels) has a shallow decay curve with a T2* value of >20 ms. … Carpenter et al36 also attempted to provide calibration in humans Brefeldin_A for cardiovascular magnetic resonance relaxation parameter R2* (reciprocal of clinically measured T2*) against actual myocardial iron concentration. They reported that myocardial R2* provides a robust curvilinear relationship when calibrated against chemically assayed values of cardiac iron in postmortem studies. They also reported that R2* mid-ventricular septal ROI was highly representative of mean global myocardial iron (figure 2). Figure 2 Adapted from Carpenter et al correlated T2* values to myocardial iron content. The regression (solid line) and 95% confidence bands (dotted lines) are shown and derived from analysis of the log-log data shown in E. (A) R2* plotted versus myocardial iron ..